Finally, IMS, is this the answer and ultimate closure.

https://m.youtube.com/watch?v=hzUq2DFpeKw Found this video on direct oil feed. It was recommended by a local well respected independent in Cape Town, a real genuine Porsche hub all things Porsche from racers to road cars across all eras and models. All in, 1200 quid to source and install. What does the forum think?

I seem to remember a much cheaper 'direct oil feed' solution which involves drilling a small hole into a nearby oil passage. Some people have cast doubt on these solutions saying that the oil will spin out under high rpm, unlike the grease that is usually encased within the dust shields.

News Flash: Titanic hits Iceberg. The IMS bearing has a direct oil feed - all you need to do is remove the dust shields. Proven by Hartech.

Loads of text on this subject in 911 & Porsche World this month. Interesting reading.

So according to Hartech, all you need to do is remove a dust shield?

When I had the clutch changed, I got the garage to remove the the IMS bearing outer seal (round plastic cover), it was already slightly worn, and was letting some oil in. Car had done about 40k miles and was nine years old at the time.

YES

...and Alex comes back with a classic uppercut response opcorn:

One of a few \smoke and mirrors' solutions.

Why is it a smoke an mirror solution? What specifically do you mean? This local independent, a highly reputable independent amongst the Porsche community in Western Cape is advocating it strongly. http://lynxmotorsport.co.za/#&panel1-2

To try and answer why there are different solutions. A ball bearing does not benefit from a pressurised oil feed it just needs a supply of fresh cool oil and to be part of a filter system to remove and small pieces of worn metal that inevitably wears off parts slowly. A linear shell bearing does need a pressurised oil supply to keep the shaft metal apart from the shell bearing material as a result of the pressure in the oil between them - without which it could seize. The sprocket diameter on the end of the shaft runs in an oil bath at up to around 4,500 rpm and the chain fitting round it also travels at up to 40mph in the same oil bath - these between them splash oil in all directions at enormous force and speed and it gets everywhere and is entirely capable of lubricating an open ball bearing nearby. In fact when the dust seal that Porsche fit has worn slightly and the grease has leaked out - the pressure and force of oil nearby is sufficient to get in and out of that minute seal lip and in most cases can lubricate the bearing sufficiently to last for up to 150K (if it was not damaged too much during the period the grease mixed with wear particles, eventually escaped and the seal lip was worn enough by then to allow oil to seep in again). You can imagine how much better that would be if the whole seal was removed. The test set up of a bearing rotating in an oil bath does not describe the actual process as the centre of the IMS bearing remains stationary and it is the outside race that rotates. it is true that a rotating disc will throw oil outwards under centripetal acceleration but the gear is many time larger than the bearing running directly in the sump oil bath and the chain running at high speed in the same oil bath throws oil against the crankcase wall where is splashes in ample quantities with much more force and volume that the small IMS bearing does in the opposite direction and so - it is entirely sufficient to lubricate the bearing. Furthermore that oil bath is a continually cooled source of fresh filtered oil - nothing more needed. The small bearing itself is just slightly under a spec that would make it reliable for 100% of all fitted with it in this application - so perhaps 99.5% reliable say but with the seal in place that reduces to perhaps 90% or so. Lots of IMS products are s old as upgrades but in our opinion the only true "upgrade" is to fit the Porsche shaft with the larger bearing or some other modified original IMS that does so. The larger later bearing is man enough for the job but once again benefits from removal of the seal on assembly - which we do during rebuilds. Baz

Start with reading this post from start to finish: http://911uk.com/viewtopic.php?t=100752 What folk fail to grasp is any roller/ball/etc. type bearing needs a fraction of the oil that a solid bearing (crankshaft bearings, etc.) need as there is no friction involved to the extent there is with solid bearings (parts roll against each other rather than rub) so the bearing need very minimum amount of oil to survive. but most importantly of all, read this bit: and also this from another post: (there's loads more from Baz on here but can't find everything) [/b]

c: Baz beat me too it!! :thumb:

Sorry Baz, I'm not technical. Is Alex Yates correct? Hartech's view is that one just removes the 'dust shields' and job done? I could arrange that tomorrow.

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Do not have your bearing removed if it isn't required!!!!! If the bearing is in situ in the engine, just remove the outer dust shield. Don't have the bearing pulled out unless it's knackered as this can do more harm than good. It'll also be a damn sight cheaper to just have the outer dust shield removed too.

Yes if your bearing was in good condition when you were inspecting it - then just removing the seal would probably enable it to last as well as anything else on the market - but that will not be for ever nor as long as the larger later bearing will last. The problem is to establish what happened to the bearing up until that point. It could have run OK (as most did) and therefore be a good scenario or it could be worn badly (although you can often see this by testing how lose the cage is and the condition of the grease if any is still in there). Unfortunately removing and refitting a bearing "in-situ" can damage other internals (even with the use of special tools) - it is unlikely but could happen but it could. However most of these engines will have a slightly shorter life expectancy that many previous Porsche models. Things like cylinder ovality and cracking, head cracks, scored bores and crankshaft bearings etc will not overall last as long as they did on average in say an SC, a 955/968 etc - and like most older Porsches of all types - will require an engine rebuild one day. So as the incidence of IMS failures is still relatively low (probably little more than some other failures and much lower than cracked, oval or scored cylinders in later models) and if it looks and seems OK - then removing the seal seems a reasonable risk with the proviso that if it did still fail a larger bearing IMS could be fitted while other things are refreshed or even improved upon (depending on who rebuilds it and the specification chosen). Current prices show just how much older Porsches are valued and so eventually rebuilds will be an acceptable part of ownership for this model range (as it is becoming for other models) and at least things can be improved while doing so. Unfortunately claims form others that their "upgrade" will last for ever could only be truly comparatively tested by reproducing what happened to the ones that failed - i.e. fit to several hundred cars and run them for thousands of miles with different owners for several years and then assess the outcome - by which time most will have needed an engine rebuild anyway - and the problem could be resolved during it. Like a lot of problems with these engines the only way to assess the value of specialists contributions is to read and judge their engineering capabilities and compare the various claims and make a judgement on that - perhaps the volume of engines they work on is a factor as well (as you would soon hear about it if they did a lot and had problems). It is a mine field however. There are specialists that put a good argument on the Internet to encourage potential customers to trust them that are poor engineers that have been involved in failures that others have had to fix afterwards, lost legal cases and had to pay compensation as a result and tried to persuade people that other specialists had done things wrong by lying about the causes of failures elsewhere - relying on running others down rather than presenting their own credentials and arguments supporting their position. Such is life and such is the business of attracting customers. You will not however see them prepared or confident enough to try and explain technical issues on the Internet nor debate technicalities as some others have. Unfortunately - it is the small number of weaknesses in this model range that is the root cause of creating a situation that unscrupulous people can exploit (and is what goes on in business everywhere) and because the background reasons were not avoided by the manufacturer they are far more complicated than most would expect and take a lot of experience and research to correct - so in this scenario - there will always be alternative solutions and technical arguments and some owners will get caught out while others will get it right and there are no easy answers - so good luck whatever you decide to do! Baz

:lol:

Okay. Thanks. I think we all put a lot of trust and reverence in what you say. It's just that I'm a bit pedantic and want to get down to some real core absolutes. Forget all the other stuff that happens to engines. I'm sure I'll want to rebuild my engine someday to upgrade it or just get it to where it can be. And someday I'll be sending my perfectly good engine to Hartech to get an even better one. But for now, just on the IMS issue, this is the big one. The one that can be sudden and catastrophic. The back of the mind issue. What I'm hearing you say, is, assuming that the IMS bearing is fine upon examination, remove dust shields. IF it's for some reason not fine, replace with standard Porsche replacement with dust shield removed. That's it? It's seems like a crazily simple solution after al these years of internet mayhem. And that applies to the 3.4 1998 model specifically which is my particularly area of interest?

If you inspect the bearing and it's fine, it'll still be in the engine so you will only have access to the outer side of the bearing - this means you will only be able to remove the outer dust shield. The one on the inside of the shaft can not be removed without removing the bearing. That's perfectly fine though because all the swilling around of the oil is on the outside face of the bearing. Do not get you mechanic to start pulling the bearing out just to remove the inner face dust shield. If the bearing is goosed and needs replacing, Porsche don't do them any more so you will need to source one from someone like SKF to the same spec. Then pull the dust shields off both sides before fitting. Bearing should only cost between £20 - £50.

I'm sort of speechless. That after millions of posts, hundreds of magazine articles and numerous videos, does it really genuinely all come down to a dust shield? After years of raging ferocious debate, do we all quietly pull a little dust shield of a single component and shuffle quietly away into the normal life, never mention it again?

In the comments below the video there is this comment that relates to your proposal. Which now seems irrelevant anyway because the bearing is perfectly well fed with oil if you remove the dust shield. "The DOF was designed to fix the problem at the lowest cost (without engine tear down heck, without even removing the engine from the car). To drill holes in the IMS as you say, you first have to remove the engine, tear it down, remove the IMS drill the holes, clean, reassemble, install. Do you think that's less than $800?"

As Chris said - All smoke and mirrors Do you get it now? :grin: There'll be some snake oil salesmen squirming in their pits reading this post with a cupboard full of 'IMS upgrades' :wink:

There's also the small point that it was never exactly a common problem anyway....... :grin: And as Baz said, all you're doing with any of this is reducing probability of component failure, as you can never eliminate it completely. The only way to reduced it to 8 sigma etc is the fitment of secondary back up systems to cope with component failure. And then you're into Nuclear Reactor / NASA territory. Warm it up properly, change the oil regularly, make sensible precautionary 'upgrades' as advised. Then like the rest of us spend most of your money on maintenance, petrol and smiles :thumbs:

......or buy a Turbo :lol:

This is the culprit:

GT3 please

Crazy talk, fool!!! What kind of madman would buy a 996 turbo and use it as a daily driver............? ut:

Apparently not! The bearing is fine, it's that oil in a small number of cases doesn't get to it and keep it lubricated. https://www.youtube.com/watch?v=hzUq2DFpeKw&app=desktop

So would you put all of these in the snake oil salesman 'reject' box. https://www.youtube.com/watch?v=hzUq2DFpeKw&app=desktop https://www.youtube.com/watch?v=zKYcfMfL-o0 https://www.youtube.com/watch?v=bS9A8y30eWc https://www.youtube.com/watch?v=MCqiYU9uU1Y [/url]https://www.youtube.com/watch?v=kCE-KnTDSvo

So conclusions so far if the undoubtedly knowlegable Alex and the legendary Baz are to be believed: 1) Direct Oil feed is a snake oil salesman ploy. Walk away. 2) After market bearing suppliers are another snake oil ploy. The original bearing is fine - just ensure point 3. 3) Every 911 owner for 98-2005 I think, needs simply to remove dust shields. Probably cost 500quid at a local garage. 4) If original bearing is showing signs of wear, replace with similar and revert to point three. Hey presto, the M96, whether single row or double row sorted. When was this simple fix figured out?

Hartech have been doing it for around 4 years.

Just for clarity - there is nothing wrong with a direct oil feed - it is just not strictly necessary and is certainly not the only or the essential modification - splash oil will work just as well. The only reliable solution is to fit the large bearing without a seal during an engine rebuild. Any other solution simply reduces the risk and extends potential lifespan - but since there is an element of variability in the way the first bearing was fitted and how tight it was when first run (and the life it had in the past regarding oil changes and type etc) - it is impossible to assess the starting condition now for anyone with a small bearing type already in the car. The bearings also in themselves have a very small quality variation that may influence longevity. The risk of failure is small and most owners will never experience a failure. Some protection may be offered by warranty or maintenance plans (like ours). We have been working on the problem of IMS failure for more than 12 years. We first discussed this with the original dual row manufacturers and obtained their last stock of spares and came up with an improved stronger spindle and replacement single row bearing kit before we knew Porsche had fitted it and provided a kit to fit the single row bearing to either a single or dual row housing. We did not advertise or market this then because some specialists we had supplied simply copied it and then we gradually realised the basic bearing was a little too small for the application and that it could damage some internals during re-fitting (and some idiots or those desperate for an affordable solution - might even try and get away with fitting one when their bearing had failed without stripping the engines - to remove all traces of debris - that could backfire). We have seen most of the "upgrades" offered to the market in here having failed and from this, calculations, test results and experience concluded that the basic space available was insufficient to hold any perfect solution. We manufactured and satisfactorily tested prototype new end gears for the shaft to suit the new larger bearing some 3-4 years ago (when prices went up) - delayed volume manufacture when they went down again and they are now in production due to Porsche supply difficulties. I think I have explained enough now and don't want to be drawn into personal arguments or issues - there are plenty of alternatives on the market and you should now have enough information to decide what to do for the best or to suit your circumstances and funding. Baz

Da-yam. My car had a new clutch 6 months ago. Could so easily have done this then. Da-yam

At the (extreme) risk of adding more fuel to the fire isn't there a missing piece of info in here which is that not all ims shafts are created equal? The bigger bearing shaft from roughly 2005 onwards is considered a much more reliable solution - especially with the dust shields removed. When I had my engine rebuilt I had the older smaller bearing and I was advised to fit the later ims shaft with the larger bearing. The feeling was after that there is no more to be done. The shaft is around £1,000 and can't be replaced without stripping the engine (obviously). As part of a rebuild it makes sense - it would be a big project to take on if you didn't need a rebuild!!

Hi Baz, There is zero argumentativeness or personalization on my behalf. I have many friends in Porsche clubs etc who are huge admirers of Hartech. I'm just looking to strip away a lot of the technical stuff for a simpleton like myself. Because there is so much back and forth about it and internationally famous magazines are constantly putting contradictory stuff out there. In the spirit of asking your advice and drawing upon your expertise could I ask a couple of questions. 1. For me personally, with a 98 3.4, would you say that just checking the bearing and then a) if it's fine put it back with the dust covers removed or B) if it's has some signs of wear, replace it with one of your replacement units - and that should be as good an action as really needed? And do you supply these replacement units or where else can people get them? To be totally honest, if happily buy a new bearing just to have it there so handy so when I get around to having my current bearing looked at purely as a precautionary mid life check up, I'd have the part there ready if needed. 2. From your experience, are the original 3.4 dual row bearings proven to be pretty reliable and the real issues came with the later single row bearings on the 3.6's? Purely in terms of the IMS bearing issue? Cheers Niall

Ooooh you bitch! That's a proper low punch :hand:

I didn't think you could fit the bigger shaft in the 5 chain 3.4 engine. :dont know: Niall - the dual row bearing in the 3.4 was more reliable. The bearing spec is also an off the shelf bearing and should be easily sourced from most bearing suppliers so I wouldn't panic about having a spare when you come to inspect yours.

What - coming from a 3.4 NA owner :dont know:

Yeah but I was just thinking, to hell with it, why not get it looked at. If I had the part in advance and needed it grand. But if u checked first, found it to be a bit worn and then went looking for the part, I'd have to have the 'zone' opened a second time. On the 3.4 v 3.6 thing, I've seen both Total911 and 911 & Porscheworld and numerous forums say the later bearings were an improvement in spite of the the US class action. I wrote to them asking them for the source of their info and never got a reply.

Well this is the failure data I collected from 911uk members cars.

I followed that great thread and it seemed that the consensus was shifting that way (not to mention the alignment to the US class action) but strangely I'm still not seeing it reflected in the mainstream Porsche media. Hence I'm curious what Baz has to say. And ultimately understand where the magazines are getting their version of the world from?

This info should be passed on to M97 owners that cannot easily replace the bearing but could remove the outer dust shield with the bearing in place.

What I'd love to get to is real simple agreed understanding for each version. 3.4 you remove shields. 3.6 you do XY. 3.6 upgrade you do ABC. 3.8 you do Z. There's so much detail often criss crossing various models not to mention the Boxsters and Cayman that for those of us with very little grasp of the mechanical stuff, it just gets long winded and overwhelming. I'd really like to simplify it for myself and maybe one or two other thickos out there.

I think you just need a different hobby.

This is why the smoke and mirrors brigade make so much money out of peddling the fear. They put up convincing arguments and they know the internet spreads stuff like wildfire. Some of the US based stuff is the worst by a long way.

There is no smoke and mirrors with us - just plain true facts. Our first introduction to M96 engine problems was with the dual row bearings. They spec slightly less than the single row because the single row has deeper groove tracks for the balls. When we ran out of dual row bearings we had to make a conversion for the single row. The double row was not (and as far as I am aware is not) available anymore and was a special design and order. Neither seemed any better than the other to us. The single row is available anywhere. You can fit a large bearing IMS but need a later crankshaft to accommodate the change to a hivo chain drive from a roller chain drive. Our new shaft ends have been made with either so enable the older crank to run with our bigger bearing shaft but you can only fit it by stripping the engine. Trying to remove and replace a small bearing in situ can cause damage and even damage the fit of the new bearing - not very likely with good tooling but very likely without. If your bearing has lasted this long the seals will have worn and the oil is getting in OK. In our experience if they last past 60 to 80 K they often go on to 150K. Unfortunately this is not a good situation for anyone and we are just trying to do our best to help in a situation we did not create. Our view is that various alternatives are no better than a single bearing but that changing the old bearing may cause more problems than it is worth if you remove the front seal (no need to remove the rear one anyway) and the track and cage look OK it might be a better risk to leave alone, remove the seal and keep your fingers crossed. If it is in tact but looks bad - replacing in situ with help may be a better risk financially than a complete engine rebuild - but you will need one of those anyway one day - so perhaps it is a risk worth taking until then? Sorry I cannot make the problem completely go away - that is the way it is! Baz

:thumb:

This guy is great at replacing the bearing and cheap too :grin:

^^^^^ Bodger central!

:floor:

:lol: When I worked at Philips, this guy would be known as a Ham-Booner.

Sorry Baz, just to be clear. I take two big things out of what you've said here. 1) My 98 3.4 would I assume have a dual row bearing. You are saying that this version is no longer available? So if I was ever to do a job on my engine I would have to replace it with a different one? What is the best replacement one? And 2) you reckon that by 80k miles my dust shield has worn away anyway at this stage so the whole idea of getting someone to remove the shield as a near preventative solution is redundant for my particular car? Cheers Niall

Thankyou to all posters very informative regarding the IMS :thumb: Now to get back on topic... I've clicked all the links on this thread and I can't find any suppliers of snake oil.... could someone point me in the right direction :dont know: :lol:

It seems that anything to do with direct oil feed is snakeskin oil. It appears that removing dust shields on existing bearings is sadly a red herring on the basis that most engines will have worn these out anyway. Replacement bearing for the original 3.4 engines are not available therefore.... ...if I was to put my car into a garage next week and ask them to do something, I'm not really sure what that would be!

It's not a red herring, it is a possibility that oil seal may have worn - it's not a definite. If you have a dual row bearing - why would you need to do something/anything if it is ok? The likelihood is (by a large percentage) that everything is ok. I understand that the technicalities can appear confusing, but if your car is ok and all is well there are some basic checks at oil change etc. that will allow you to keep an eye on things. Why not just e-mail Baz direct or PM him. There are options which he will discuss in detail.

I probably will give him a call actually because sifting through even a short burst of posts on a thread like this immediately begins to throw up contradictions and possible waffle. So on the shields Baz is quite definitive actually. He doesn't use the phrase 'might' but rather 'will.' See quite below. If Baz is correct the whole 'just remove the dust shield' line is irrelevant to 90% of cars. 'If your bearing has lasted this long the seals will have worn and the oil is getting in OK. In our experience if they last past 60 to 80 K they often go on to 150K.' The reason I would have my dual row bearing checked is simple. I could be in the 1 or 2% that fail. Surely the most sensible thing to do after 80k miles is simple - have a precautionary look and check up. Just in case. Why not? Every year something has to be done. Next week the air conditioning has to be fixed. So for something so important, why not spend a bit of money every five years or so and look at it as part of a big service item. The question for me is, if there is signs of wear, what is the right action to take? I honestly thought, based on advice from a local independent and the video I posted that there might have be a nice simple precaution in DOF. But that option has been shot down here which obviously now makes me wonder what is going on with the local 'highly reputable' indie!

Do not doubt that the indie you mention has a good reputation and many satisfied customers - there are lots of indies that fall into this category. Just because they offer the DOF and other 'fixes' does not make them bad in my book, the internet has fed a lot of paranoia and if customers ask fr this (and others) or they get incentives/publicity for offering these 'fixes' then they are a business at the end of the day. The percentage of Porsche owners who take a technical interest in their cars oe get 'spanners on' is low and the market is rife for this kind of thing.

If a DOF is completely unnecessary as has been ardently argued then Indies recommending them for 'business' is in my view extremely bad. Not only is it a rip off, but it's a very deliberate feed into the hysteria which then gets amplified by the magazines. And it should be called out. I have no problem with indies promoting their business around fixes they genuinely believe in and know to be valid. I welcome that wholeheartedly. At the end of the day, DOF either is valid or not. Someone is right and someone is wrong.

Indeed - my view (and others) is they are wrong, along with the ceramic bearing pedlars as well. I have no commercial interest and am happy to speak out. Simple fixes, very rare issue - end of.

Well, with a quick glance I see that one of the regular advertisers on 911UK promote them (Design 911) and I see another company, Revolution-Porsche-co.uk promoting them. I see that he moderator on Pelican is 'dubious.' On the RPMTechnik site they promote the L&N bearing replacement who in turn argue against the DOF. I'd like to hear Design911's response!

Just because people sell a solution to a sizeable market, doesn't mean to say that solution is worthwhile..... In the US people spend over $5 billion dollars a year on homeopathy. By comparison Baz's post is the least 'homeopathic' contribution I've seen yet on IMSB failure :dont know:

Couldn't agree more. To be totally honest, I was quite tempted to go with the DOF. To a non technical person, it seemed to make sense. A little addition popped into the engine bay. not a big job. But I think I've saved myself a grand here so thanks to all. But it makes me more determined to to get to a simple honest real conclusion. In the meantime, I look at someone like Design911 now with a degree of cynicism. IF they can't back up the part, and seemingly it can't be backed up, then selling a fix that doesn't do anything is basically fraud or at best extremely lazy crass opportunism.

The marketing line behind Precision Porsche Specialist (advert on top of page). (L&N supplier) So you have to ask yourself one question. Do I feel lucky. Well, do you?

As a matter of interest, what's their take on it? I can't get a copy here at the moment.

I'd like to think it's the latter. But given that a US based Pharma company selling a 'natural' herbal based remedy recently dumped all its stock onto the market cheap ahead of an FDA ruling banning it from further manufacture because of established links to liver problems, you can never discount pure sh1tty greed.so the former is lost possible :nooo:

+1 ps. Chill and stop waffling (OP not you Chris), you're starting to sound like one of the scare-mongering internet snake-oil salesmen.

Sorry but I don't agree with that assessment. The OP is merely exploring options. What's wrong with that? :dont know: OP, this month's '911 & Porsche World' (page 82) gives a really comprehensive overview of the M96 engine and some more sage insights from Hartech. :thumb:

Hold on a second. You're the guy who waded in with your big banners and billboard proclamations to the world about it all being just a simple solution, pull of the dust shields, that's all you need to do - 'Hartech agree with me' line. As it turns out, thanks to a bit of clarity from someone who knows what their talking about, Baz - the shields wear off anyway. WTF! Seriously, what were you thinking when you mindlessly splashed up your half truth onto the thread? What else have you been putting out there? Another poster referenced drilling holes in your engine! Yours was the kind of toxic ***** post contaminating the web, oddballs who think they know it all proclaiming all sorts of half baked ideas that quickly collapse under a bit of scrutiny but then stay there forever on the net. We'll probably be reading Total911 articles for another five years telling second hand 996 buyers to 'just remove the dust shields' until your particular contribution to the lexicon of crap washes finally through the system after many others have to sift through it tirelessly and methodically before dumping your myth for good. You're part of the problem. These are just brilliant engines that only really need a particular component resolution to make them not just fantastic but completely robust. I'm seeking that resolution strategy. Whether it's a new this or that, oil feeds or L&N bearings, I don't care. I'm happy to put a bit of money in. Just as I would be to replace worn bushes, or a creaky coffin arm. A headlight cost me 1000K. So it's nothing in my view to spend a couple of hundred once ever 80K miles to get the bearing checked and then do whatever is the best thing to do. It should be routine. I'll keep asking what I want to ask. And I'd ask that until you actually know truly what you're talking about, you desist from submitting your attention seeking made up answers and leave it to actual experts or genuinely informed enthusiasts we can trust. It's a serious subject. Not for internet messers. And a proper Porsche forum os the place where the real solutions should be identified and the snake oil salesmen (as above) called out. Back to the forum. So the question remains. 3.4 C2. running like a dream. Great track day at Killarney Gardens last week. Never a problem. And I'm not one of those drivers who checks their oil every week and 'gently warms her up.' Car is a keeper and guaranteed future classic as far as I'm concerned so I want to steadily keep it tip top and hope it gives another 80K amazing miles and ten years without issues. Next week I'm getting the air con fixed. And it occurred to me, while the car is in, is there anything I could do about the IMSB? I saw the DOF video. Looked good to me but apparently it's nonsense. Dust shields are worn away. So what other options are out there that are simple, genuine and not hysteria inspired opportunistic fake solutions. Reasonable question on a Porsche forum?

I think your question has been answered several times over! REMOVE THE FRONT SEAL

Eh wrong. Maybe read the thread properly next time.. "If your bearing has lasted this long the seals will have worn and the oil is getting in OK . In our experience if they last past 60 to 80 K they often go on to 150K. My car is >80K.

Apologies if that drunken comment at 12.20am fuelled by two bottles of red on a school night touched a nerve. Simple answer is - remove the dust shield if the bearing is still in good shape, if not, have it replaced. and don't kid yourself with an open comment like "Baz - the shields wear off anyway" Please reference where that statement came from? As for all the offensive waffle in this post above - no comment. I was only trying to help and educate you about the myths of exploding IMS bearings. Next time I'll not bother Niall996 Have a nice day.

Excuse me. You piled in with this piece of crass ignorance out of the blue, from nowhere. " ps. Chill and stop waffling (OP not you Chris), you're starting to sound like one of the scare-mongering internet snake-oil salesmen." Re the reference you've asked for, it's quoted above, twice. Have a nice day yourself.

I don't have time to read through everything I have ever posted but I don't recall ever saying that the dust shields "wear away" (if I did let me correct it now) they just eventually wear at the lip enough to start letting some debris out and some oil in. After looking at hundreds we have replaced over recent years we have seen some with grease still in (very low mileage), some with a mixture of grease oil and small bits of metal looking like grinding paste, most with no grease, some metal and some oil and a few very high mileage ones with no grease, no metal and a reasonable amount of oil. The seal is always still there - just no longer a tight fit against the journal. Our conclusion is that if they survive past a certain mileage they seem then to carry on for longer and the explanation of the seal fit wear fits that scenario. Set against a very low risk anyway (even less if the car is already higher mileage) and bearing in mind (excuse the pun) that the engines will be much more likely to need to be rebuilt one day than will fail with the IMS bearing and that the larger bearing seems a permanent fix - the removal of the seal to a bearing that happens to still be running Ok to increase oil supply and cooling affect seems to me a pretty good gamble. If I had to design a fix without stripping the engine and money was no limiting factor I think it would be a solid bronze bearing running on a solid ground shaft with a direct oil supply from an auxiliary oil pump. The only reason I would not do that without the auxiliary oil pump is because the oil pumps are very crude and at low revs when the engine is hot deliver relatively low oil pressure. We already know that the crankshaft shells need replacing at around 80 to 100 K in the 3.4 + engines and say 120+ in the smaller Boxsters (almost always worn through to the base shell metal in the centres by then) and if we steal an oil feed from that pump it will lower the pressure on hot tickover - which we would want to avoid if possible. The original double row bearing was a special made for Porsche only. Because it had two rows it generated a greater proportion of "running in" metal dust particles and ran hotter so it did fail in the early cars. The single row replacement is a standard readily available bearing but because the interference fit in the housing is tight and because many damage the ground surface through "age Brinelling" or marking on assembly and because of the minute differences in the size of the housing interference fit - it is better to specify a looser version than a more high precision one to maintain some clearance. You cannot fit the single row directly but lots of people now make fitting kits (as we did years ago before the accumulation of evidence of general failures and the increasing appreciation of the lower than normal life expectancy of the engines - deterred us). We didn't retain our version because we were concerned about damage during fitting and only wanted to fit ours ourselves - so we didn't make a fuss when other copied or modified our original design as we were reluctant to be involved in anything that could backfire. Replacing a bearing (even with a puller kit) can cause problems. We made a support tube to prevent the shaft pulling too far outwards and dragging the chain into the slightly worn track it has got used to running in on the plastic tensioner runners - because we had rebuilt some engines that had had a bearing replaced elsewhere and the debris had got into other parts of the engine and in one case blocked the crankshaft oil feed hole. Fitting the new bearing back in is also difficult because even if you remove both chain tensioners (that alone has resulted in some people having the cam chains jump their timing) you are now pushing the shaft back inwards further than it usually runs and this can damage those tensioner runner tracks in the other direction. The tension left in the chains also means that at the same point that the carrier is trying to go in the crankcase it is also trying to fit over the original spindle that has a recess for an "O" ring and this can crack the spindle. Our kit always had a stronger spindle without the same "O" ring but instead a different seal internally. We have replaced several bearings in situ but we don't like doing it and will not be responsible if something else fails afterwards because it is impossible to be sure damage has not already occurred, or happened during the removal and re-fit and we don't want to let customers down nor be responsible for a complete engine rebuild because we decided to try and fit a replacement bearing in situ knowing the dangers (and more importantly seeing the results of other peoples failures). I would guess that for most people they would be lucky enough to get away with replacing the bearing in situ with care and some special tooling - but it will not always happen (because we have seen the actual evidence) and since we already believe any bearing replacement on the market will be no better than the original and since the numbers failing are dropping now that the early low mileage failures are behind us and most engines have covered enough miles for the remaining ones to be judged reasonably OK - and because most of our work is rebuilding engines and we can supply a larger bearing shaft for either roller or Hivo crankshafts - we think it best to leave others to carry out the "replacement in situ work" - if that is what they prefer to do rather than try to help only to have it fail. To make it clear - what would you do if we replaced your bearing and (for example) a few weeks later one of your cam chains snapped, a big end went, the bearing housing leaked etc. In our experience anything that goes wrong that is in any way connected with the engine is perceived by some as always the fault of someone else and in this litigious society of ours it would no doubt fall back on us or generate bad publicity. For example - just this week we had a call from someone claiming we fitted an IMS bearing to his engine a couple of years ago and that it had now failed and what were we going to do about it - however - fortunately for us - our records printed on his receipt for work we did do - showed that as a result of our thorough approach - we actually pointed out to the owner at the time that he already had a bearing already fitted by someone else previously and that he declined to do anything about. This is typical of why we are sensitive to what we do and what we offer to customers. These are potentially great engines in superb cars with a few small weaknesses that we do stick our necks out and design solutions for, invest in efficiency measures to make them affordable and provide a genuine warranty for excellent service that has enabled our reputation to speak for itself. Where we can do something worthwhile we do everything we can to help but this particular IMS small bearing in situ replacement with a similar sized solution is just not one we want to promote as a 100% reliable solution (like our others are) and we offer technical and real life explanations as to why. Those with an engineering background usually understand and go with us but those without mechanical sympathy are in a difficult position - but it is no good getting angry with us or our posts nor exaggerating or twisting what we said just to vent your anger at a situation we did not create and don't see an easy fix all for. Good luck with whatever you all decide to do for the best. Baz

Actually you can still remove the front seal, it will give more oil splash than just a worn seal alone. Doing it as part of a clutch change would be the most cost effective time to do it. I think you just want to keep the debate going, and annoy as many people as possible.

Actually you can still remove the front seal, it will give more oil splash than just a worn seal alone. Doing it as part of a clutch change would be the most cost effective time to do it. I think you just want to keep the debate going, and annoy as many people as possible.

That is interesting. By the way, on the annoying other people part, if that's related to putting up 'yet another thread' on IMS I can understand how that makes people feel. It used to piss me off frankly to see so many IMS threads, especially from suspiciously 'new' posters. It seemed like cars were blowing up all over the place. And then you'd never hear from those posters again. I had the sense that the whole thing was being hyped artificially - and overtly by charlatan garages and trolls. To such an extent, that the 99% rest of the car was forgotten. And I wouldn't be surprised if there are snake oil salesmen & charlatans peddling the latest US 'cure' popping into 911uk now and then to start and IMS thread. It doesn't bother me now however. For a couple of reasons. I've seen a marked shift in terms of how the 996 is seen over the last two years. The other 99% is being recognized ad talked about at last. The brilliance of the driving experience, actual reliability, build quality etc. More and more are starting to view it visually in a whole new light as well. It's passing through that window into classic'dom and finding it's own place. The only real impediment to a sort of complete renaissance in my mind is this damned IMSB Achilles heel. Talking about the past, talking about %'s of cars affected, talking about when and how it's most likely to strike all drive the hysteria in my view. Talking about simple fixes negates the hysteria however. Brilliant car - just add xy & z and it's totally sorted. That's what I want to find, hear more about and chat about. Solutions. Do this and your engine is as safe as any other engine. And then there should be a stickie on it. And anyone who ever has a doubt about buying a 996/7 Boxster/Cayman because of IMSB should be able to pop in and quickly see what the Porsche Enthusiast/Porsche Expert community agree on. And eventually the magazines might catch up. Right now magazines are using phrases like "thankfully there are many solutions out there now" without any real insight or authentic knowledge. Which actually is a negative. I'd like to see that change to 'here's what you need to do and that's it.' And eventually it might be a non subject for good.

I understand the arguments here, there is not one simple solution that can guarantee the IMS will last forever, its more about what you can do to help its longevity. So is the L&N ceramic bearing option not thought off as worthwhile and has anyone had issues with it?

Here: http://rennlist.com/forums/996-foru...ceramic-ims-bearing-failure-at-30k-miles.html and here: I've seen a few others too. When it happens, both LN and the Indy blame the other party.

Overhyped, overpriced and not without its own problems.

Thanks, mine was replaced as RMS was getting done before I bought the car so need to check which one was put in. As said before it does also appear that incorrect installation could lead to premature wear.

Hi Baz, This is the line you wrote which I take to mean, perhaps incorrectly, that once your mileage reaches a certain level, the seals are worn away anyway. In other words, taking the gearbox off to access and remove said shield would be pointless and not offer any additional security. "If your bearing has lasted this long the seals will have worn and the oil is getting in OK. In our experience if they last past 60 to 80 K they often go on to 150K." Some really interesting elements in your last post. 1) "and that the larger bearing seems a permanent fix." - Am I reading this correctly. Would you recommend that anyone with a 3.4 when getting say a clutch done should pop the 'larger bearing' in. Are these something Porsche supply? 2) "but this particular IMS small bearing in situ replacement with a similar sized solution is just not one we want to promote as a 100% reliable solution." - Do you mean the L&N bearing or what would a IMS small bearing replacement be? I have my car booked in to the local Cape Town Porsche Centre for next Friday for air con fix. I rang up the service dept. there and asked, a) how much would it cost just to check and diagnose and b) what type of bearing would they put in my car where they to replace it. He's gone off to check so I'm waiting on that but it would be great to understand what typically are being used to replace original 1998 dual bearings (small bearings?). 3) "We have replaced several bearings in situ but we don't like doing it" - I take from this that regardless of the bearing type, you don't advocate changing in situ (which is a really cost effective way). And my understanding is that the process of changing in situ can cause problems elsewhere. Is this a correct understanding - that it's not a good thing to change in situ full stop. That's a bit concerning. 4) "We already know that the crankshaft shells need replacing at around 80 to 100 K in the 3.4 + engines" - This one gave me a bit of a fright, I hadn't come across this before. My car is just gone 80K+ and you believe crankshaft shells will soon need replacing. What are they? Thanks Niall

The larger bearing cannot be fitted without totally dissembling the engine as it dosent fit through the ims cover plate/ opening (as seen once the engine and gbox are separated). Also going that route would limit your options in the future if the new larger bearing required changing (possible as it still just a bearing) in situ so it's a double edged sword. When you do require engine removal then remove the bearing seal and check for play, replace if needed with like for like and continue to monitor. It can be done in situ but care needs to be taken as the new bearing is fitted by applying pressure to the ims which will move forwards unsupported inside the engine casing. Don't get too hung up on this whole ims subject. For now keep the oils clean (I change mine every 5k) and topped right up on the dipstick, monitor the oil filter for debris. As has been mentioned before aside from the ims bearing issue what are you doing about the other engine failure modes?? Snapped timing chains, d chunked cylinders, bore scoring and ovality, cracked heads, blown out cylinder head core plugs, burnt exhaust valves, failed air oil separator etc. Everything will needed rebuilding at some point but how you treat the motor day today will dictate how soon that is. :thumb:

Cheers for the answer. Funnily enough, I had my oil topped right up on the dipstick to when I brought it to the track. The pro drivers there advised me it was too high and oil would get sloshed out somewhere from the g-forces. So I've since keep it mid level basically - when I do check. On the IMS as a, lets say core interest, you have to bear in mind the context. My car is going into a garage anyway next week so I started thinking about taking the opportunity to have it checked. And the follow up question is, what if it was a bit worn? The key thing about an IMSB is that when it goes, it does so with catastrophic consequences. Many other things can go wrong with car engines I know but generally when a car starts to show issues, you get it fixed. You have warning. And generally speaking, to my understanding, once reasonably well maintained these engines are pretty bulletproof. There aren't huge issues around "Snapped timing chains, d chunked cylinders, bore scoring and ovality, cracked heads, blown out cylinder head core plugs, burnt exhaust valves, failed air oil separator etc." You make the engines sound like complete wimps. That's not my experience at all. IMSB is the core Achilles heel and the little component most in need of future proofing. Perhaps it's living in Cape Town. It's one thing having a catastrophic engine breakage along the high street. It's another on the N2 outside Khayelitsha Township on the way back from the airport at night. There are some places where breaking down is not an option. So I'd like to future proof (e.g. get another 100K) out of the IMSB. That's the core question. Do we future proof with oil feed? No. Do we future proof by maintaining the car as we go? Hmm, maybe, not sure that would get a universal thumbs up. I think some would argue that some very well maintained cars still went pop in the past. Do we future proof with magnetic detecting devices on the sump etc.? Not sure about that. Or my own discipline in checking filters and stuff. Do we future proof with popping in a new IMSB every 80-100K? Now that sounds a runner surely? Simple, convenient, logical. Having said that, Porsche Centre Cape Town haven't rang m back yet to confirm what bearing they would put in if I needed/opted for a new one. So I'm not quite sure what would go in. I presume the 'large' one you're talking about is a later 997 bearing? My double row doesn't seem to be available anymore which seems to leave me with two options, the potentially discredited L&N (see Alex's post above) or the single row 3.6 version that replaced the double row? Minus the shields. I think!

Running below full (oil) can run the real risk of oil starvation on the track due to G forces. Run it full always. 2nd option is baffled motorsport sump, third is dry sump.

Actually, on reflection I think I was over full with oil, above the max, not full. You're correct.

Hmmm. Given what you have said and asked. Ok, firstly - you need to do some preventative stuff as a matter of routine. Oil and filter every couple of thousand miles if you are tracking the car. The IMS shaft and bearing is not necessarily the achilles heel if you have attained the mileage you have without problems. It is not something that can be checked and the best process you can do is unravel the oil filter element at your frequent oil changes and see if there are metal particles in there. If there are then maybe you need to look at the bearing, if not then leave it until the next oil change. The Air/Oil Separator (AOS) is something you need to consider changing if it has not been done in your ownership - not sure if you can do your own spanner stuff? - if you can then it massively reduces the cost (these are not difficult cars to work on).

Dry sump is not practical on the M96 for packaging reasons plus the engine was never designed to run with negative crank case pressure which is one of the main reasons (aside from oil control) for going dry sump in the first place i.e. improvements in ring pack sealing. I'm now running X51 style baffles which seem to make the grand total of naff all difference on my logger but then I always ran .5L over fill anyway compared to most as mine is an early one which I believe have a higher oil capacity than later cars.... If you're somewhere near the top of the dipstick and on road tyres then you should be absolutely fine

Thanks a mill. I'll d that. Well I'll ask the garage to do it. Check the oil filter element. Seems like a simple interim check. On the Air/Oil separator, one garage did say to me that it needed to be changed. However, another garage told me (without looking at it by the way) that you would have see a burst of white smoke out the back on start up if there was any issue there. Which I never do. Does that mean anything to you? Is it a significant component? I've heard of it but never really known what it does.

I've been around tracks many times with what I would describe as really superb amateur drivers in their GT3's and some tuned track modified M3's. Then I had the experience a couple of weeks ago being driven around a track by a professional Porsche racing driver in my humble stock C2 and it was, and I say this with all due respect to the excellent amatuer drivers I had encountered, utterly off the scale. What he did with the car will be seared in my mind forever. But here's the thing. I've never had an oil issue but after three laps the back of the car was completely sprayed with oil and on certain hard corners (well they were all epically hard) some smoke emerged from one side under acceleration. Apparently Killarney is a tough circuit because every corner bar one is a right hander, a couple are really tight, and it has an effect on non dry sump cars. Anyway. We chose to leave it at that and let the car cool. Which it did and since then, not a peep out of her. Completely as always was, no issues, no wayward oil, normal and strong as ever. I think I had overfilled the oil. Another comment was that the extreme loads (unbelievably extreme) had possibly exposed a not so perfect seal here and there. Anything familiar sounding in that?

Mine is the 3.6 and I replaced the single row bearing as could detect some slight play ( interestingly engine was out for other reasons as posted, but not clutch or rms leaks, other modes of failure do happen and are more likely once the ims issue is addressed as more miles pile on but don't be put off). Perhaps it's slightly misleading to say check the filter for debris as I had no debris but wouldn't have left the bearing even with the seal removed. Chances are it would have gone beyond the 112k or so it had on it at that time, but for £8.50 it was a no brainer to replace and now I always check the filter for debris The main dealer will not offer a bearing replacement in situ as it comes as part of the ims as an assy so again complete engine strip at OPC. Yes was referring to the late model 997 bearing being too large to be retrofitable (without complete disassembly) . You can convert to a single row I believe but other parts such as new ims cover plate and centre support stud would be required so as a first port of call I would check to see if a bearing supplier can deliver a replacement bearing to existing double row spec. Oil pickup can be iffy so worth running at upper dipstick limit as I've seen the pressure gauge flickering on hard and fast long sweeping bends. There are baffles in the sump that try and keep oil at the pickup but it's a pretty basic design. Just my thoughts from lessonsed learned so far and others experiences on here. :thumb:

FFS. Having a real struggle with the local Porsche Centre. It's like talking extract cold war secrets from the CIA. Basically I'm asking them, if I asked you to check my bearing next week, and we found that it needed to be replaced (let's just say there's a little too much play or the bearings are showing wear) then what would you put in? What replacement part have you got? So the guy who runs the service department just blanked me saying they've never had the problem ever. And that he knew nothing of IMSB parts etc. Eventually he put me through to the parts department who told me there are only two parts available (other than the American L&N). Part number 99610502401 and 99610502401. When I googled them I keep getting IMS flange. (and beautiful and shiny and perfect it looks too). When I asked the parts department does the actual 'bearing' come as part of the flange or is the flange just the holding part they said initially, no, there's no bearing, the IMS shaft just 'slides on' like one slightly wider tube sliding over a slightly narrower short little tube. When I pressed him a bit and said that the bearing was possibly the most famous 911 engine component in the world and was he absolutely sure there was no 'bearing' with the flange unit he threw in the towel and said he didn't really know. They'd never needed one. So basically no one at Porsche Centre can definitely tell me what part they have or can get if I needed to replace my dual row IMSB.

I would have been shocked if they were able to answer your question TBH. OPC's are generally a waste of time with this level of technical query - they generally work by swapping big bits not individual components.

So from what I can conclude so far, drawing upon the wisdom of 911UK. With regards to a 3.4 1998 Dual Bearing IMSB. Totally open to correction. 1) The car is 80K and 99% trustworthy anyway. At some point maybe in the mid 100's or so, after many years of amazing performance, something may give at which point the car is due a bit of TLC anyway.Who knows what technology may be available in 2025 anyway! Could be a good thing. 2) If by some rare fluke there was an issue right now with my bearing, it's probably due to my maintenance habits rather than the engine itself. 3) Oil is the life blood. It's a high performance engine. Look after it regularly. 4) Check the filter 'element' now and then. 5) Direct Oil feeds are either a) Useless or B) no harm, do it if you like but still useless.Basically a big thumbs down of the OP. 6) The dual bearing is gone. No longer available. If you want to pop a new one in as amid term freshen up, it'll be a later single row. 7) Because changing bearings can in itself pose a risk (dodgy installation) it's not advisable. Only to be done really if there really is a case for it - actual evidence of an affected in situ bearing. 8) If there are still dust shields, take them off. They're more a hinderance than help. 9) L&N bearings are pointless. 10) Over the next 80K a lot of other things are going to need attention as per normal with any cars going into high mileage. 11) SO bottom line, for an 80K 3.4, only think of checking if something is in the oil or the clutch is getting changed. and then, pop in a regular new single row bearing. Does that sound about right?

Good summary. Works for me! :thumb:

Yes a good summary. I wouldn't say that LN or pumped oil were no good - just that the bearing space is too small and we do not consider any fix as good as it would have been if the original had been bigger - so all much the same and probably not worth spending too much for no clear long term benefit as a result. Failure is probably almost random bad luck as long as you keep your oil level correct, Yes if there are signs of the bearing failing but not yet gone - probably worth risking a change - or do the job properly with an engine rebuild - but remember the dual row bearing was wider so you need more than a narrower single row bearing to replace it - you need a spacer and different spindle or collar as a kit to fit it into the deeper space remaining. Roller bearings do provide more radial load margins but less axial and chains do actually flap sideways as well as in the direction of travel. We have seen ball bearings cracked around the circumference indicating that the side loads were significant - so I don't think anyone can quantify the exact loadings nor which would be best - my hunch is a ball bearing that does both jobs best. You don't need to remove the rear seal as fresh oil can only get in and out from the outside. In fact possibly best leave it if the bearing is being left in as the old oil trapped inside the IMS becomes poor quality and if you cannot get it out (as you would during a rebuild) best allow it to stay where it is. Baz

Having just bought my first 911 (a 2002 3.6 manual cab) a couple of weeks ago, I have found this subject very interesting. I looked at buying a 996 about 6 years ago but ended up buying another 968 instead. The reason: I visited Hartec and was appalled at the amount of 996's in the workshop having engine rebuilds due to IMS failure. Thus as a precaution I'm having some work done on this 996 at local indie (D&G motor engineers): upgraded bearings (think they might be roller???) and a lower temp thermostat. Is this appropriate? For the relatively low cost it seems like good sense. Am I missing anything? The car will not be tracked or have too hard a life - it will be runabout (keeping 968 for best) / wife's car Also no idea of car's previous history (bought it because it was a steal) Cheers Paul

You think? I would find out exactly what they are suggesting!

What's the mileage? I'd be getting the bores checked before you throw any money at it, could be a wasted exercise. Personally I'd also steer clear of changing the bearing if the old one is fine, especially for a roller one that doesn't support any side forces.

It's done just over 73k (just out of interest what's the going price perception on here? It's got MO30 and a few bits of supposedly fancy trim along with special leather generally decent condition. Polar silver, metropole blue and grey interior and I gave the guard top.) The indie seems to know what they are doing Regarding bores, how does the scoring problem manifest itself? I've done about 400 miles in it since I picked it up and it drives fine

Oil consumption, black smoke at startup and left sooty tailpipe. I'm guessing you paid about £12k - £13k?

8.5k

WOW!!!!!!! At that price you can afford an engine rebuild and still not be too fleeced. My plan of action would be: 1. Get the bores checked. 2. If OK get a low temp. stat. (if not, start saving for an engine rebuild, preferably with Hartech for the added peace of mind and to retain value). 3. Get the oil changed and stay regimental with the oil changes, warming up, hammering it, etc. 4. Inspect the oil filter for any debris or particles. 5. Wait patiently for a time when the gearbox needs to come off and when it happens, get your bearing checked out and if ok outer seal removed. Personally, as you've probable already read my previous toxic myth, I wouldn't pull a bearing that was in satisfactory condition. Oh, missed the first and most important point :duh: Get a new post started in the newbie section (or this 996 section) with your story and plenty of photos of the beast!!!!! :grin: ps. Welcome to 911uk.com :bye:

Baz quote: so where would you source the spindle/collar & spacer to go along with the bearing if the need arose to replace a dual row bearing with a single row bearing? Does someone sell this as a kit or do you buy a suitable bearing from a bearing supplier and purchase the other items elsewhere - and if so where - or do you get an engineering shop to manufacture a spacer/collar? Has this being explained before as I can't recall reading about it in previous threads, thanks.

Thanks for the advice - I will post some pics after it's been at the detailer (following it's current trip to the indie) The indie has checked the bores and they are fine. The IMS upgrade he's doing involves roller bearings (he reckons naff all lateral stress) and an oil feed. Few more questions, is the MO30 suspension as well regarded in 996 circles as it is for 968's? Is it just a suspension upgrade or brakes too? How much of a ball-ache is it fitting and removing the hard top? Cheers Paul

For those concerned about the quantity of oil required to lubricate ball/ roller bearings, just remember that most 2 stroke cranks are lubricated by a very fine oil mist in the crankcase.

Save your money mate for the other jobs you'll need it for.

Just the standard brakes as far as I'm aware. The hardtop is quite easy if there's 2 of you but near on impossible on your own.

As Alex has posted, I would give the situation a rethink - ball bearing (rather than roller) is the way to go and forget the oil feed.

We should be spreading this message about the dust seals far and wide, don't you think? Would do a lot of good for the image of the 996 (and 997.1 and 986, I presume). Pistonheads and Honest John come to mind.

Gents, the perception is that these cars are fragile creatures because of the IMS. I've seen with my own eyes how full the workshop at Hartech can be with IMS failures. That's why these cars are now worth peanuts (a decent 944 is worth more). I realise that there is probably a vested interest on here to dispel this reputation as it adversely affects values (I have sympathy for any poor ***** that paid more than 10k for one). I do however feel that for the price of a set of tyres, an upgrade to a known problem is worthwhile. If it doesn't work then c'est la vie, I will take it up with the indie.

To the OP, as you can imagine this subject has been discussed many times and there are some conclusions pretty much set in stone, take the advice given. There is not much lateral movement but there is a bit and that is enough to potentially make the difference.

No mention of that in the 911 and Porsche World Mag. Article pretty difficult to follow and not very well presented imo - needs labelled schematics and exploded diagrams of the engine and its components, not just a random selection of images scattered about the page. The information was obviously sourced from lots of places and then cobbled together, the wording on the cover states that the preventative work is 'essential'. I'm pretty sure this isn't what Baz et. al are saying - well not for the IMS bearing anyway! I'm an Engineer and have rebuilt many engines, but even for me this was a difficult article to read. I think for the average reader this will act as a warning to stay away from the M96 engined cars rather than an informative read. The bit with Sid in was good though :thumb: Paul (is only my opinion, so please don't lynch me)

Hi Paul and welcome from the rest of the NE members. The M030 is suspension only - can forward you more tech details of exactly what it entailed if you PM me with your e-mail. All the 40th AE had it fitted as standard. Hopefully see you on one of the regular NE runs sometime. Cheers..........Ian

Cheers Ian, PM sent (I think)

No reply to my above post yet, any of you knowledgable folk know? My 90,000m yr 2000 C2 allegedly has a dual row bearing and if it is showing signs of wear come clutch change time it would be handy to know where to get the parts. It would also add to the knowledge in this thread, ta?

They are not off the shelf components but I'm sure a call to Hartech will put you in the right direction.

Nothing to do with retained value from my perspective. It's about getting the right fix - if you were to take it to Hartech they would not be putting a roller bearing in nor would they advise fitting an oil feed.

Especially when the 'right fix' is cheaper than what your Indy is 'selling' you. The saving would be the equivalent of having a new clutch fitted.

I'm sorry, I have to disagree. There may possibly be a degree of consensus among a few here on this particular forum who see 'conclusions set in stone' but in the wider world, there is a vast labyrinth of conjecture, misinformation and confusion. So much so, that what might be agreed upon here bears no similarly to what is stated in the Porsche magazines, numerous online forums, you tube channels etc. One has to ask why, of the conclusions are so well established as you state, that is the case? In fact to be really honest, there is some clear contradictions being expressed even within the conclusions of the set in stone group, an indeed in this very thread. There is no simple stickie thread identifying the agreed solution for example on 911UK. There are long threads often filled with complex detail that is way over the head of the average owner whose more into driving that taking engines apart. Threads that often wander and meander endlessly with no real simple clear conclusions. So in my opinion there is still work to be done in the area of clarifying solutions. And for those who squirm ever time they see a IMS thread I would say that a simple solution orientated IMS thread (and one that clearly differentiates between the versions affected) would be a very positive thing for the values of these cars. The problem is not the engine at all but the fog of misinformation and contradiction surrounding and which continues to be replicated, fabricated and propogated literally weekly. A key facet of 'conclusions set in stone' is that they become de facto truths that are not really truths at all but accepted myths that people get very upset abut when challenged. Emperors new cloths type conclusions to be frank.They may have absolutely zero causality (e.g. the revs you use immediately after start up) but who can ever argue that it's not a good thing to warm an engine up gently (even if it has nothing whatsoever to do with IMS).

Although they wouldn't exactly completely totally dismiss it out of hand - i think.

You raise an interesting point Niall. FWIW my perspective is pretty straight forward. Firstly, there are not many people who do their own spanner work on their Porsche and not many who have an understanding of the technicalities involved. This leaves the market almost at the mercy of people peddling solutions. Some of them are very good and perhaps 'peddling' is being unkind but you get what I mean. Some of them are not hugely good and simply push what somebody else has told them is the best solution. Most motoring journo's are not technically minded particularly - they are media people interested in cars. Often articles are compounded versions of what was originally intended or they are made up of a series of other related material. Bias or emphasis can often mislead or give the wrong conclusions by virtue of this. Then there is the internet..................not much to say really!. Good as though it is I am sure we have all seen the 'I am looking for personal experience on X' followed by 'you need Y' and I had it once and loved it, worst thing I ever did etc........ Where does this leave somebody wanting to wade through the mire? Personally I would take the advice being given by Baz as being the most sensible and free from top spin around. I appreciate that not everybody can use them geographically but they are happy to give advice over the phone.

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For even more clarity there is nothing wrong with a "direct oil feed" from a separate source (I did not say from the existing source) - but there could be some minor harm if it came from the existing oil pump and in so doing lowered delivery volumes and pressures elsewhere at hot tickover! This is something I would find hard to prove even if I wanted to (which I don't) it is just that when you have a weak area in any engine that you are trying to cure - the last thing you should ever do is introduce something that "could" with reasonable assessment and technical reasoning make things even very slightly worse. These are generally good engines that after increasing the capacity and not carrying out other changes that would reasonably be expected to coincide with it (like keeping a reliable piston coating, increasing the thickness of the liner, supporting the top of the liner in a closed deck, improving the coolant flow and moving the thermostat to the outlet (oh and adding a control to any third radiator fitted aftermarket), do in some cases fail. All the above can be corrected during a rebuild that incorporates all the right mods and technical changes but there is no need to add a pumped oil supply to the IMS ball bearing (only unless it is being replaced by a solid bush when it would be essential) and in so doing it might reduce oil pressure elsewhere. Baz

Hi Baz, I totally appreciate your interventions and general contribution. Unfortunately me and I suspect 'a lot' of others on here aren't really anywhere near the technical level you are at and I can imagine that this can be frustrating for you at times. It must get tedious to keep getting asked for 'clarification' but here goes anyway. When you say 'separate source' I don't really understand that. It sounds like a seperate oil pump? And thus, with regard to the OP video and any other DOF stuff I've seen, they all seem, to my eyes, effectively running from the same ultimate source. So my interpretation is that any after market DOF running off the existing system or oil pump, is bad. (Reduces pressure elsewhere potentially). However if you replace a ball bearing IMSB with a non ball bearing version, or as you describe it, a 'solid bush,' then DOF is essential. Now, to get into some nitty gritty, what would a solid bush replacement be? I haven't heard this term. All I've heard of are single and double row bearing IMSB's. Earlier and later. Large and small. I've never heard he term 'solid bush.' What is a solid bush bearing? Where do you get them? Are they a proven replacement? And if you got one, and then had to add the direct pumped oil feed which you say would be essential , what one would you use? Where do you get them? Or am I just not getting this at all?

A solid bearing is a solid bush (usually made of a softer material than steel, like brass or phosfer bronze) instead of moving parts that roll against each other. These type of bearings create a lot of friction as they are solid parts that rub against other solid parts. The other end of the ims runs on a solid bearing, but this is acceptable as it's next to the oil pump so there is plenty of lubrication there. The other end of the shaft doesn't have that high supply of oil so Porsche fitted a ball bearing type bearing (the legendary IMS bearing). This would have been fine if they didn't fit seals on the sides and let the splashing engine oil lubricate it and if it was a more robust bearing, but they didn't. Solid bearings are much stronger but wear much quicker (especially if not lubricated correctly). Baz has suggested a solid bearing at this end of the shaft for that reason - STRENGTH. But unfortunately, the whole oil delivery for both ends of the shaft would need redesigning (as a high cost and then another high cost on the engine modification). This is not an option for the average Porsche 996 owner. All bearing were solid bearings before frictionless ball/roller bearing were invented. They are cr4p, but serve a purpose, especially where sometimes frictionless bearings can not handle the job. Frictionless Bearing: Solid Bearing: Do you get it now?

Do I get it now? Yes, from a nice to know perspective in terms of the merits of different bearing types but not necessarily from a relevancy perspective. It raises more questions for me. Is there even such a thing as a solid bush bearing available for a 3.4? I haven't come across it before. If there isn't then it's pointless even talking about it. If it does exist and it's a real option so long as it can be lubricated, and there's a lubrication solution. then that's interesting. But I'm not sure if this is just hypothetical engineering chat or an actual product? To me it's all relative. We spend loads of money on lots of things from tyres to brake pads, clear headlights instead of Amber, all sorts of stuff without complaint. I cracked a headlight and a new one was a thousand quid. The last service I had at an OPC was over a thousand quid. I had to replace my radiators once. A thousand quid give or take. I scraped my bumper. 500quud. I don't have a problem spending a grand or two on something that will strengthen my most important component, my engine, and giving that key vulnerable part another 80k/100k of life. We're lucky with 996'd in that we don't really have to worry about corrosion or many other issues unlike other 911's. The car is so reliable in every other respect its a real luxury to be able to focus on such a small number of elements. I really see it as one of the last great analogue road warriors and just want to make sure it stays that way. I don't lose sleep over it. Frankly I'm pretty confident from everything I've read and experienced that the car has tens of thousands of miles left in it anyway regardless of what I do. I assume my seals have worn and it's happily getting splash oil every day I drive it. But I want to make it an ongoing rolling restoration project. It's a keeper and it's worth my while to keep it tip top. I will probably buy another Porsche but I won't be selling or trading in this one. Hence my OP! Is a DOF, as espoused by the guy in the video and a highly reputable local indie a good idea? So far, I'm taking it that it's not necessary but I don't think it's exactly clear why it isn't a good idea. Especially as all roads seem to lead to lubrication, not the bearing per se. So is there a solid bush bearing available and if so, what would one need to do to ensure lubrication? Maybe the cost would seem excessive to one individual but would make reasonable sense to another.

As for the solid bush for a replacement for the IMSB, there won't be one available, too much space to fill and the IMS would have to be haevily modified. The other thing is the cost of development, you can't just machine a solid brass bush and expect it to work without fail, there needs to be hours of bench testing and road testing due to all the variables involved. There could be too much end float for the chains to cope with and the issue of how it wears even with a direct oil feed. There could be problems with the direct oil feed due to losing pressure when the engine oil is getting thin/hot at high temps. The reason I follow what Hartech say with some respect is due to the thousands of hours in developing what they suggest are suitable solutions. They have tried various ways around the problem and maybe have come up with the best (that it can be) already without going the BIG bearing route (seal removed), the BIG bearing is a solution already tried and tested, so spend your money there, all you would need is a gasket set and the labour to strip, rebuild and a new big IMS bearing, peanuts. Anyone can make a video and claim its a solution without facts to back it up. My favorite one is the guy spinning the IMSB in engine oil as if to say it needs to be permanently dipped in the oil or its flinging all the oil off, this is just so untrue and misleading to anyone worried about their engine exploding.

One would interpret the line from Baz quoted below that there is such a thing as a solid bush bearing. Otherwise why mention something that doesn't exist? Or is this just more theoretical science of mechanics for those interested in theoretical science of mechanics. What if's and maybes? A lot of us just want to know what preventative solution is available on the market now that has the endorsement of well respected experts (e.g Hartech) and is not in the snake oil salesman category. I'm not seeking to establish an engineering company looking to enter the market for engineered and machined IMS solutions. Hmm...now there's an idea.

There is - it's on the other side of the shaft. Didn't you read my previous post? One end has a solid bearing because the oil supply there is good and the other end has a ball bearing because the oil supply isn't good enough for a solid bearing.

solid IMS bearing/bush hi first proper post, hope its not to controversial !! while I was researching known issues with 996's before I brought mine I came across this website, so there does appear to be a solid bush replacement for the bearing http://theimssolution.com/ I don't know the merits of it, it looks well thought out and available in the UK via www.fastforward-automotive.com . don't know if Hartech are aware of this and what their view of it would be? phill

Been discussed may times (have a play with the search box on the forum)- general feeling is this is not all that is claimed and a very expensive way of 'fixing' things with a limited life. Unfortunately these discussions have a habit of going round in circles (not pointing the finger BTW).

IMHO this has been a terrific thread: 1) It's allowed people to genuinely explore what they do and importantly DON'T know. 2) Knowledgable forum member 'experts' have mostly listened to what less knowledgable but curious members have asked. 3) Yet again Baz has illustrated patiently, elegantly and humbly his deep insight. Most impressive for me as a scientist is his willingness to limit what he does and doesn't know. As well as remaining open to new ideas and understanding. That humility of approach when 'peeling the onion' of a rare but real problem gives more confidence in the findings than any number stats. Respect to you Baz :salut: :thumbs: to all and great to witness. And a long way from 2014's 'IMS Wars: The Sandals Awaken' :floor:

:agree:

I personally am only interested in THE bearing, the one we're all talking about. There isn't (although I see another post has popped in potentially disagreeing) a solid bearing alternative to THE IMSB so it's irrelevant to even bring it up. I say as I go to read the new post from Phil62. Perhaps the plot will thicken further.

Re: solid IMS bearing/bush As a complete thicko when it comes to mechanics I have to admit, when I see a video like that, I just fall totally for it. It looks like a perfect solution. Nest, simple, inexpensive. A long way from engine rebuilds and all that mallarky. And surely an instantaneous renaissance in 996 values and esteem. Nothing in my brain gives me any warning signs to the contrary. BUT, DAMN, it doesn't fit my car (3.4) so it's not relevant unfortunately. But I'd love to know what's wrong with it or why wouldn't it work as suggested. In reality, how many people from this forum have actually tried it out and have a real evidential reason to doubt it? Or are people just being dismissive for the sake of it. Would this device actually be any worse than what's there already? Baz, could Hartech actually make a solid bearing to replace dual row 3.4 ball bearing bearings? I'll buy one in titanium.

The biggest problem I have found in trying to explain technical issues is that there are usually a number of contributory factors influencing each of the typical failures that to understand - demand knowledge and experience in different engineering fields and technologies. This potentially makes explanations too long or has omissions that someone expert in just that field pick up on or invite anyone without enough knowledge in one small area commented on to question it and start a debate or argument which and degrades the overall contribution for lack on knowledge elsewhere. There are all sorts of solutions I could invent for this bearing problem - different ones and expensive ones - but the fact remains that all this engine range will have cylinder bores gradually going oval and some will have (or be about to get) first signs of cylinder scoring, while others will have big end and main bearings reaching the end of their useful life. Yes some will also have an imminent IMS bearing problem but only a very small percentage during any one persons ownership. This all means that we get very few engines to repair for IMS bearing failure and a hell of a lot more for the above general engine failures (including as well cracked cylinders and heads, broken timing chains and a few with dropped valve seats etc). Since the most reliable solution we have come across is the bigger bearing (and since we manufacture a new end to fit it to either a HIVO or a ROLLER chain crankshaft - and since this will be less expensive than the Porsche current large bearing IMS shaft) - it seems to me that risking the failure of your IMS bearing is a reasonable risk and as fitting any version of a replacement for the small bearing also incorporates risks but that fitting one of the two larger bearing versions during an engine rebuild that will crop up for most eventually - is by far the best risk. With our investment and organisation plus the future proofing modifications and additional products we fit - it seems to me that to re-manufacture these engines at a price around half that of a typical air cooled 911 (and at the same time permanently fix most if not all of the faults including the IMS problem) is a better option - especially as they are going to fail in increasing numbers as they age and mileage increases - but values of older Porsches with "good engines" are going up and these will be no different. Why risk fitting another bearing (when plenty of the "upgrades" still fail and fitting can cause problems) when very few fail anyway and a far greater number of engines will fail anyway (usually for different reasons) and need repairing when an inexpensive good fix of the larger bearing can be done at the same time? Incidentally we had another IMS bearing failure in this week - but again not an original bearing but someone else's "upgrade". In view of all this - debating all sorts of different solutions and claims seems particularly wasteful of time and energy - especially when a lot of claims are factually rubbish! I would only fit a replacement in situ if it was clear mine was failing, had not actually failed yet (and not distributed any debris around the engine) and I could not afford a rebuild anyway - and then I would only allow someone to do it with special tools made for the job and experience. I would then choose a plain single row bearing with the outer seal removed on the grounds that it should last long enough for the next problem to be an engine rebuild anyway and not the new IMS bearing. Other choices of replacement bearing probably have similar life expectancy but often would cost more. If mine was running OK I would remove the outer seal only if and when I had the flywheel off for some other reason and leave it alone and risk it lasting as long as I need it too (which it almost certainly will) and if it or something else in my engine failed I would then replace it with the larger bearing alternative. This would be a better option than paying a lot for a different solution - finding that failed or my engine had to come apart for another reason - when I would have preferred to fit the larger bearing shaft than the "upgrade" I had recently paid over the odds for. Any other discussions have been general engineering comments. Baz

Titanium is not a good material for making solid bush bearings. There would be nothing to control any end float if solid bush bearing types were fitted at both ends - same issue with fitting a roller bearing on the clutch end.

And the winning answer of this whole thread goes to Baz Hart! A+++ on a slightly different not, but same outcome, my clutch has just gone this afternoon, so I shall be making good use of the access to the IMS and checking everything out. :sad: :clap:

I feel your pain Alex :sad:

While the winning prize for 'Getting into a lather because the OP doesn't take his word as 'gospel'? would go to..........? :chin: Actually I didn't realise that threads had 'winning answers'. Or is that another innovation we're looking to import from 'Sh1ttonheads'? :dont know: Sorry if that offends you but......Alex, seriously? :duh: EDIT - Sorry to hear about your clutch. All those drag racing starts away from the local curry house have clearly taken their toll! :wink:

Nothing offends me mate. If it did, I still wouldn't be commenting on this thread would I. It was meant as a joke Paul as the whole 8 page thread (I thought) was intended as - what to do if you want to 'improve/upgrade' your ims bearing's life & performance. Baz's simple & straight comment answers all that in a nutshell & IMHO should be plastered in every Porsche 911/996 magazine, book, website, forum, Indy, OPC, owners club toilet wall, etc. etc. in the world and not dismissed as toxic rubbish to poison the internet for the rest of days, etc, etc, etc. :thumb:

TBH I completely get why this (and a couple of other) subjects get continually recycled. The information posted by some of those with a big commercial interest provides a pretty compelling argument (especially if one is not hugely technical or mechanically minded). It's a hard sell and provided much fear and loathing... I think this thread has narrowed things down nicely and Baz's selfless advice has given some very simple and understandable waypoints for an owners fear/timeline.

From reports in the internet (!!!) they would fail suddenly and spectacularly all the time, or would there e some indications that they are on their way out.

For what it's worth it was Hartech (not sure if it was Baz) that scared me off 996's a fees years ago. I left either the impression they were fragile and the IMS issue was a time bomb in about 10% of them.

That does not accord with what Baz has posted now or in the past? This kind of thing is what fuels the issues unnecessarily - rumours and 'I'm not sure' is the worst kind of contribution, sorry but it is not helpful or informative in the slightest.

That was my understanding as well. You're just driving along, there's a momentary rattle and then the engine is goosed. So a) you're stranded who knows where, B) you're facing a probably huge unplanned bill and C) you're without your Porsche for weeks.

Don't you just love the internet......! Actually, just set it on fire and claim it was stolen :wack:

We are not only aware of all the types mentioned (thanks) but have seen most of them having failed. I am not recommending a solid bush - quite the opposite - but it would work perfectly well with an oil delivery source (the crankshaft uses a flat face half circular flat shell bearing against a flat journal with an oil pump supply - to resist the strength of the clutch pull when operating it - no problem! The lateral loads on the IMS are not established but a ball bearing is designed to work both ways and with a splash oil supply and we have had discussions with a lifetime bearing manufacturing executive (who happened to spend a lot of time researching all the options and available bearings and owns a Boxster S) and he agreed that he thought it would need something better than a flat roller bearing end face (unless it also had a pressure oil feed) - but no one will have tested enough to destruction to confirm or deny anything - except that we receive and repair 4 to 5 engines/week (which has increased from around 2 to 3/week a few years ago) and I think the feedback this provides about the condition of original bearings, worn bearings and different IMS kits combined with our basic engineering knowledge is about as good a clue as to what the true situation is that anyone could provide. You may remember (or can check back and find) that we were very unimpressed with a idea of a ceramic type many years ago (before they were in general use and known to fail) and have had two in here having failed in the last few weeks - I seem to remember we suggested they would be no better than the cheaper std bearing (possible worse?). But you must appreciate (as we do) those specialists that try and provide solutions for problems that the manufacturer should have sorted out for their customers first. Usually spending money to genuinely try and find excellent solutions (and I do think they are more motivated by a belief in the success of their product and how it will help owners than doing it purely for commercial rewards) - but if the main manufacturer with a superb reputation can get it wrong - it is expecting a lot for most general technician specialists to find a better solution on much more limited funds in with far less test opportunities and resources. So I prefer not to knock those that don't always get it right while being frank about the difficulties some problems create that are often almost impossible to improve without huge expense and modifications. The IMS bearing is a difficult problem to improve on in the space available without huge cost while the larger ball bearing seems (from all feedback and experience) to be totally reliable (and is available). What to do will unfortunately always be a gamble and it is the odds that should influence decision making. Unless there is an obvious reason to get into the smaller bearing in situ - I suggest it is a better bet to ignore it (or take the seal out if you are close by with the flywheel off and know what to do so you don't loose cam timing and can replace the outer carrier without straining the weak spindle). If you were lucky enough to find the bearing damaged but having spread no debris anywhere - it must be worth carefully replacing the bearing and spindle. We are reluctant to retail our replacement bearing, spacer and spindle kit because we suspect some owners will damage their engines trying to fit it (or have a premature failure later) but we will do so ourselves if requested - but without our usual cast iron guarantees. There are plenty of others now with their own kits that are prepared to fit them for their customers. I think this whole range of cars are really superb - among the very best cars (on the whole) that Porsche ever produced and far less expensive than they would have been if the engines were more reliable - in fact - looked at in numbers - they represent superb buys with relatively little risk - and if you are unfortunate enough to suffer a failure - it is not too expensive to not only repair it but also improve those weak areas to result in an even better car that will appreciate in value. It would seem to me to be a great shame to spend a lot on an apparent IMS "upgrade" only to find that later the engine needs rebuilding anyway and could have then been fitted with a much better solution for little more cost at the same time. You must make allowances when I offer replies that sometimes I am referring to a theoretical issue someone has raised, or countering an incorrect technical conclusion or opinion and not always discussing what to do. Unfortunately there is no good easy reliable permanent answer to the IMS small bearing issue without stripping and rebuilding the engine but plenty of good reliable and affordable "upgrades" if the engine is apart - as long as you also avoid those issues where some specialists do (probably out of ignorance or greed) promote a solution that has been proven to be short lived and often results in an engine requiring a second rebuild shortly after the first. Baz

Look, I enjoyed Alex's Alleluia Moment red quotation and it is a great quote. Very simple layman's language and coming from a recognised expert. And I would happily be an ardent advocate of the advise on internet forums and toilet walls the world over. The car is about to make its fourth international move shortly and there'll be whole new community there to engage with. It'll have travelled more miles in a ship container than on the road over the last five years! But, there has to be a but doesn't there! A lot of other things in Baz's post leapt out at me which I'll go back to later but for now, just sticking with the core point of the thread, the IMSB and preventive measures.The basic thrust is essentially leave the IMSB alone and only bother with the seal if the flywheel is off for another reason. That is in itself a very solid statement. Even I can understand that. My 'but' here is this. If the advise is also at the same time to replace it (if needed) with a larger bearing should there be a reason to open the engine anyway then why not do it as a preventative if one wants to fork out the cash? I get the point about inexperienced mechanics without the right tools potentially doing a botch job which in itself would render the choice a very poor one. But let's say someone rocks up to Hartech tomorrow morning and asks for the simple larger bearing to be put in? With all of Hartech's experience to hand etc. How much would that cost? I'm guessing about a grand but only guessing. Would that not be a very good thing to do? It sounds reasonable to me. Like I said in a previous post, it cost me a grand fro a new headlight! When my coffee arms began to creak I got them changed. It comes with the territory. Unfortunately Hartech is not an option for me as I don't live anywhere near Hartech and I wouldn't give it to anyone to do who wasn't highly reputable. So I'm not going to go down that route but it might be of interest to UK owner within range. The real 'jump out' part of the post though for me and I suspect many others is the main thrust of the post that in all likelihood other stuff is going to go on the engine and really, a full rebuild has a sort of inevitability about it. As Baz says, they get loads of engines in and the IMS issue is actually ultra rare. Now I'm getting worried about the other stuff although at least they sound like things that give warning. I get the point about hysteria about one component and the really these engines are more holistic devices as any great performance engines would be. And that snake oil solutions are are a massive cloud of nonsense in the context of high mileage engines that are approaching much more significant needs. Like a patient with chronic heart disease worried only about getting a filling sorted.They may offer something, but it's not the issue. Although I still cling a bit to the idea of 'prevention.' It's a question for a separate thread probably but from Hartech's experience, what sort of mileage are we talking about where lets say a 3.4 will reach that state if inevitability? If we park the whole IMSB thing, then what are we really looking at? The cars have been around for 17 years now so there is hopefully a sense of their longevity. Mines at 80K and I would have hoped that at least another 40K wasn't asking too much? If the reality is that M96 engines generally get to the end of their 'first life' without the IMSB ever being an issue then the natural follow up question is what is that life expectancy? I've seen several 996's go to over 200K. Is the fact that there are many engines arriving into Hartech due to the fact that there are simply s lot of 996's now in the 120K zone? The common line about M96 engines is that apart from the IMSB they are pretty robust.The general commentary is that air cooled engines and Metzer engines are virtually indestructible and M96's would be if it weren't for the IMSB? I'm a bit thrown by the idea that the IMSB is the least thing to worry about? I'm happy to book my engine in for a rebuild in 2025 but I wan't planning on it being needed for a long while yet. The other thing that caught my eye was this line: Why qualify the statement with the bit about 'during any one person's ownership? I was surprised as well to read that air cooled engines are more costly to rebuild. I would have thought that they were simpler and easier?

You are really over analysing stuff - seriously!. You will never make it invincible - the difficulty for you is the country you will be in, the bias and the preferred 'solutions'. Take the highlights from this thread, do frequent oil and filter changes and enjoy!.

I don't think anything I have posted here contradicts what we expected a few years ago now - that about 10% with the smaller bearings will have problems in their lifetime (by which I mean say 15 to 20 years in which time they will have had say 5 to 8 owners bringing the statistics of chance of failure in you ownership down to just over 1%. The only difference to that is that we could not anticipate then what we have seen since - basically that if the bearing survives past say 70 to 80K it seems that by then many have worn the small seal edge enough to allow an increasing amount of fresh oil to get in and actually last longer on the improved supply than we expected then. A few years ago it looked like a straight line graph mileage to failure with a range of perhaps 50K form extremes. Now there is a different view - many have been correctly rebuilt and improved already, others have the larger bearing, some have some other solution that because it is relatively new - although overall it may not last any longer than the original - still has years to failure left in it and all these changes have influenced the statistics and with it our advice. It took a few more years and higher mileage cars to inspect - to see for ourselves and work out why on average higher mileage engines seem to then last longer on the original bearing. I also cannot see anything that contradicts the likelihood that most owners will either never have a problem or have a sudden failure. The chances of finding a bearing in tact but sufficiently damaged to encourage a replacement - but not yet damaged enough to spew debris around the engine - is extremely remote. This forum is a place for information, comment, discussion and the opportunity to explore alternatives and ideas. It can be helpful and useful but it can also be used to release anger and frustration, self promote and advertise poor quality advice or solutions and attempted retribution. We offer our best (but honest) advice as impartially as we possibly can. We defend unfair, inaccurate or defamatory comments (which is our right) and we try and avoid criticism of others products or opinions directly by name or implication (except in exceptional circumstances) but what we cannot do is alter the reality that the small IMS bearing is a weakness (all be it a rare one) and that other weaknesses, the difficulty of finding an easy improved solution and the suddenness of a failure are how it is (sorry). There is no easy answer and owners and readers must make up their own minds who to believe and what to do for the best. If I was not involved in the Porsche market but had studied this problem I would still think the cars are well worth owning and well worth the risk. If I had one I would either ignore or replace the bearing (as I could do it reasonably reliably but would accept it if that failed for any reason it could have been my fault and perhaps I should have left it alone). If I didn't have a lot of engineering experience or tooling and was not comfortable with such a job - I would honestly ignore it in the certain knowledge that I would have to be very unlucky for it to catch me out - but if it did I would be pleased that a good job could then be done to improve my engine in my appreciating superb sports car that cost me very little to buy! and generally less than I expected up until then to look after. Baz

To me it's just one of those risks that you take when buying one. Enjoy the car, change oil and do what has been suggested but otherwise don't worry about it. Almost every high end car will have an issue of sorts that can happen. My Rs4 if the cams wear it's about £4-5k to fix, turbos are £2-3k as well etc etc but the chance is small so I just enjoy the car and take that risk because it's worth it.

I reckon that as an individual the OP may be unsuited to 996 ownership. With the greatest respect a slight devil may care/happy go lucky attitude is probably useful. Noticing a few ex bikers like myself and I'm not surprised. Worrying about every issue is pointless and will simply ruin you're ownership experience. Drive it like you stole it, blow it up, rebuild it with larger capacity.....repeat.

Lol, I think your right. Im an ex biker/racer as well.

Yeah lads, let's just trash them and be damned. The 996 way. Lets not replace brake pads or oil or any of that stuff for wimps. Rock on!

Hi, yes I raced a bit too. I meant no disrespect of course but na engines are difficult to tune or improve upon. I'm looking forward to to my rebuild as a rare opportunity to make real improvements to the performance. The turbo boys are spending a mint without complaint. I'm saving this money and plan to buy cc's with it. Keep her lit. Si

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The aircooled engines also had their fair share of disastrous problems and it's unfair to compare an engine that was continuously developed between '63 and '97 or so with one that in 996.1 form was 1st generation and all new. Take the advise given (follow precautionary steps) and worry only when the engine needs a rebuild, otherwise you will erode the experience of ownership. If Hartech are a long way away but are your prefer'd choice at rebuild time I would have the engine removed, palletted and shipped to them for repair. Alex, sorry to hear the clutch has given up, what's the mileage now? I bet you can't wait to have a look at the imsb though (get a swap thread going). :thumb:

:thumb:, remember to wait until the tyres have wires poking out as well. That's helps with traction so I hear. All Im saying is mitigate to a reasonable extent where you can but don't over think or worry too much about this. The chances are there but its an acceptable risk to take IMO otherwise it will spoil your ownership.

What's the going rate on a rebuild?

http://www.hartech.org/porsche_996_997_Boxster_engine_failure_repair_rebuilds_prices.html

The irony is, I'm not actually a worried 996 owner. Never have been, at least not until Baz's post about the rest of the engine imploding before the IMSB will be an issue! If anything, my local indie used to berate me for not checking my oil, tyre pressures etc. I just get in and drive. Have no mechanical knowledge and was basically just interested if there was anything on the market worth considering as a way to extend the life of the engine. And I can assure you, the car gets driven as I alluded to i this topic. http://911uk.com/viewtopic.php?t=107416 Investigating engine mods whether as performance enhancements or life preserving preventative maintenance and dipping into the experience of others doesn't make a person a worrier. It's a sign of an ever growing affection for the car!

I'n not really sure what this really involves but it seems quite reasonable if it is an actual engine rebuild. Might be a nice 100K miles present for one's car. Base Engine Rebuild (Engine Only): £2200 + VAT Comprising of: Strip engine, clean & prepare for re-build, re-assemble with all new gaskets/seals (except valve stem oil seals at this stage).

OK now I'm getting confused. Are we now saying that the larger bearing is more reliable? Does this not contradict the general findings that more 996.2 engines with the large bearing failed compared with 996.1 with the dual row? Not that dual row owners can replace like with like anyway - but for Base engine reliability... Or is there another large bearing from the 997.2(? I understand that engine cracked it) that can be fitted and solves the issues (with seals removed)

There is another larger (or taller) bearing that requires the crankcases to be split to be fitted, the other two are just single row 996 3.6 and double row 996 3.4 standard diameter.

:thumbs:

:hand: Now my dear friend. You know that's not true. There is a solution to have the larger bearing fitted without splitting the engine. Watch the clip in this link: http://www.vertexauto.com/ShowItem/343829 Porsche IMS Boring Tool for Installing IMS Bearing.aspx :lol: :grin: :floor:

^^^^^^ I cannot watch this c:

Of course, I'd forgotten about that process, and fitting the new bearing is as simple as anything, you need a mallet and drift.

It's like a cross between "Hostel", "Death Proof" & "The Dentist" The whizzy drill noise right at the end :yuk: The next few posts should be a good read :grin:

My thoughts exactly. When you posted it up I thought, Nooooooo what have you done, then I just thought, it should make for good reading over the Christmas period.

:thumb: :lol:

Does this prove that roller bearings are the way to go due to them being easier to knock in with a hammer?

Yes, but only if it's a calibrated hammer.

This is one of the many reasons I do not believe anything that the American 'Specialists' say when they are offering Porsche improvements/solutions......

Quite right. I for one am assured and slightly sheepish in light of my earlier comments. No hard feelings I hope. Si

I see someone has resurrected this thread and in it 911uK forum users are advocating a Low Temperature Thermometer (no, I don't know what that is either or why the car just doesn't come with one in the first place) which didn't get mentioned once here as far as I can recall. It shows how different stuff gets put out there and the varying advice can be a bit confusing to the non mechanical amongst us whereas I'm sure it all makes perfect sense to the engineers/mechanics. http://911uk.com/viewtopic.php?t=101457&postdays=0&postorder=asc&highlight=m96&start=20

The low temp stat is one of things recommended to reduce bore score. I don't think it has anything to do with IMS. :thumb:

.......and isn't really relevant for the 3.4l engine.

Ah, ok. Thanks

That is seriously uncomfortable viewing.

This thread has been a great read, thanks to all that participated. In particular, thank you Baz for your balanced and knowledgeable contributions. As a new Porsche owner it's refreshing to hear a non-commercial, and open minded approach to these cars.

:thumbs:

I was just browsing some of the magazines and came across this pearl of wisdom from someone called Josh Barnett. And here's the irony. He's a writer in a very well known magazine called Total911, devoted to all things 911, a big fan of the 911, Total911 is a magazine that exists because the 911 exists. You would think the staff there would know a thing or two about 911's. But he wouldn't buy a 997! Nope. IMS. Deal breaker. This isn't internet forum hysteria but the supposedly sensible reasoning print media who continuously driving the scare story of IMS. Meanwhile the other two writers had no issue choosing a 997 as their top 30K version. For any potential buyer who is relatively new to the 911 world, you can imagine how confusing it must be. "I was close to choosing a 997.1 Carrera 2S like Lee, however the (very unlikely) possibility of IMS failure still puts me off." http://www.total911.com/the-total-911-teams-ideal-30000-porsche-911-garage/

I used to read Total911. Emphasis on used . '911&Porsche World' and 'GT Porsche' I still rate very highly though. :thumbs:

Total911 did a big buyers guide on the 996 C4S recently, maybe only three or four months ago. In it, they were absolutely categorical in stating that the 3.6 was the far more reliable improved unit over the 3.4. I sent an email to them asking for the source of their information. I was curious as to how they had come to this conclusion. Its a big big statement to make in world full of fans enthusiasts an potential buyers all looking for clarity and the essential facts. A big statement without a shred of evidence as far as i can tell. We can handle the truth! We just need to know what it is. Never got a reply.

They are no different to the majority of the media - mediocre at best. It's all about selling copies and advertising revenue - the truth and technical accuracy are not really at the top of the list.

Their editorial technical interest is woeful so sadly not surprised. I'm no Gina Purcell fan that's for sure. Thing is Niall, there is always a baseline of unreliability with any Porsche. And that baseline for 911's has always been lower than you'd expect for the budgets or the volume involved. A 911 of the 997 or 996 era even with an engine rebuild is still a total cost bargain. But the vast majority of spend (in the high 90's % mark) will be most likely on fuel, tyres, suspension parts and servicing. All will need engne work at some point. But that's only because they (as a model) last so long. Over time all parts wear and will need repairing or replacement. Bore scoring I personally classify as premature ageing so bringing forward what would be an inevitable expense anyway. This has been a great thread and has confirmed to me what wonderful machines the 996/997 series are. I suspect we're 5-7 years out from an engine build going from 75-100% of total vehicle value for the NB cars (50-80% for WB) to under 30% for all. Then it'll all be about 'boats missed' etc :thumbs:

Just stumbled across this and thought I'd post it here for all members who'd like a better understanding about removal of the ims bearing outer seal. It's a nice little 'how to' showing what's involved and a great little video explaining the situation: (might shed some light on the issue for anyone not technically minded) http://specialtycarsservicecenter.com/projects/cars-2/2006-997-m97-engine-ims-bearing-seal-removal/

Apologies if I'm talking bollocks but aren't the bearings designed to be lubricated by grease not oil? Wouldn't ingress of oil wash out whatever grease is in there?

The sealed in grease turns into a grinding paste over time and the longer lasting bearings seem to be the ones that have let a little oil in over time to wash the grease out, better still is a bearing without seals that lets fresh oil in daily.

My two penneth......new bearing, no seals, DOF kit. Belt and braces? who knows but a bearing with both splash and forced oil feed gives me peace of mind. Search "my ims tale" on Pistonheads for pics/story. Regards.

It's unnecessary - the bearing sits in oil.

Are you sure it "sits in oil"?

Yes. Just look at the heights of the bottom of the sump to the IMS shaft centre and the volume of oil you have in the sump. Add to this the violent throwing around that the sump oil gets the only shortage of lubrication is a sealed bearing. As Baz has posted, in many engines the oils seals age and the seals shrink which allows the grease oil and the engine oil in. The issue is the fact that the original bearing has seals back and front. Once you get this, just read the stuff that Hartech have posted.

I was also going to comment on this but you beat me to it Chris. I have measured the distance from the bottom of the sump to the top of the IMS (I can't remember the figure off hand) but it was below the oil line at rest. This is a picture of my engine with split crankcases and showing the bottom of the sump to the relation of the IMS, add nearly two gallons of oil and there you have it, way above the IMS.

^^^^ Thanks Chris :thumbs:

Chris & Chris - I never gave it a thought, will I have to drop my oil if I remove the ims cover plate? I should be doing it tomorrow if all goes to plan and it never entered my head about the oil depth.

Thanks Chris, that's a better situation than I had envisaged....I presumed the lower edge of the bearing was submerged but the upper majority of the bearing was out of the oil at rest (that will teach me to read American websites!) My question "are you sure" was a genuine enquiry and not meant to sound confrontational as I'm here to learn not argue the toss as many seem to be. I really rate my car and am keen to keep it running well for as long as possible hence the extra precaution of the DOF kit. As I previously posted...probably belt and braces but hopefully any extra lubrication should help.

^^^^ You might get a bit of seepage but it's going through the bearing. Stuff a microfibre cloth/blue roll against it if it gets excessive.

:thumbs:

:thumb: :worship:

Hope you've got a big cloth :lol: When you release the IMS cover the IMS face and the holes in the pulley will soon flow oil, compare this picture with my previous one and you will see how low the chain is in line with the sump. The story of the little boy with his finger in a Dyke comes to mind, no not that one the one in Holland. I will admit I've never seen a disaster story of someone removing the IMS cover with an engine full of oil but then I'm not sure I'd admit it if I'd done it. Go for it and I'll bring my camera. :camera: :success:

Well the thing is it isn't just American websites when it comes to DOF if that's what you mean. It's everywhere, forums all over he world. And it's on UK forums and magazines. In fact there are companies who are regular advertisers in 911uk who advocate it. Does that make it a reasonable viable option for owners looking for a bit of extra peace of mind? Apparently not - it's a bit of a snake oil salesmen concoction but you can imagine how confusing it gets for average joe to navigate through it all. And f course it's in the UK magazines a lot. For example, 911&PorscheWorld did a full page on it recently (issue 258) where Mr Johhny Tippler (the journo who so often slagged off 996's but has now bought one) added a DOF first thing (even though his IMSB was perfect). So he 'who do you believe' question is a valid one always with this subject because it flows back and forth continuously. Again, casually reading through the same issue, you come across all sorts of big statements. Page 74, stay away from 997 Carrera S models. 'It's not a case of if but when they will lunch themselves. Get a 3.6 instead.' Page 152, same issue. 'The original 3.4 was beset with problems that have been detailed many times by 911&PW. ..however...the C4S is 'sorted with the later and much improved 3.6litre engine.' Now i saw a post on here from Alex in some thread telling people to run a mile from 3.6's. And then there were the class action results. Plus I also wrote to 911&PW enquiring where they got their data from. Again, like Total911, no reply. On a side note, in the same issue again, letters page, a really exciting individual called John Towler felt it really vital and important that he write to the magazine to argue that 996 values while creeping up now I'll fall back down again when people realize the engine issues aren't going away and there are interior trim build quality issues! Obviously Johnnhad a lot on that day in the office or old folks home. So there you go, the endless back and forth continues. Magazines and mechanics leading he charge and the actual owners left scratching their heads trying to get to some sort of core basic incontestable truths. By the way, in the same issue again Steve Bennet give the 996 3.4 a rave review and his answer to IMSB? He doesn't exactly specify what he means but basically on page 65 says 'the car had a clutch change so could have had 'the fix. But there's no way to be sure so he'll get it done 'for peace of mind.' And who is an average Joe Public owner to disagree with professional Porsche 911 journalists who are immersed in the world of 911's and all the related trade contacts, club contacts, owners, engineers etc etc day in day out. And so the search goes on

Cheers Chris (the other one). I've sorted a cloth, although I think I'll drop the oil just in case :grin:

OPC are immersed in the world of 911s, but from what you told us - they didn't have a clue about the ims bearing :dont know: The issue with the bigger engines of 996 & 997 NA cars is mostly bore scoring due to cylinder 6 not getting cooled properly by the system. Much, much bigger than any ims problems. That's why the average Joe (who in total has spent millions on engine rebuilds) will tell you the 3.4 is the less troublesome engine. Are all the magazines and journalists sponsored by the companies inventing these 'upgrades'? :?:

Maybe drop the oil then Alex............. :coat:

The journalists are just that = they might be working for a Renault or BMW magazine next. I usually ignore what they regurgitate if it's anything technical and it's one of the reasons I rarely buy magazines these days. They often do not understand what they are printing and to some extent it's about them supporting firms that advertise and give them revenue.

Going back to my comment on oil level compared to the IMS bearing position and wanting to prove my (educated) theory correct, today I got a spare crankcase half I had lying around, like you do and got the tape measure out, I measured the engine oil dipstick tube from my 996 and deducted this length from the the length of the dipstick. I dropped what would be left of the dipstick into the same line the dipstick would run, give or take a few mm. I used a straight edge to show the line at the top of the IMS opening the results are below. I took some pictures and you will see the upper oil level mark on the dipstick is about level with the top of the IMSB cover opening meaning the bearing which is much smaller than this hole is deep into engine oil if you keep the engine topped up to the brim as I always do. Straight edge in white going from top of IMS cover opening and passing through the top level of the dipstick. Obviously engine oil, once the engine is running is spread around the engine but there is always a good quantity in the sump still and easily enough to lubricate the bearing as it really does only require a small amount to lube it. Using these pictures and my two previous together and hopefully that answers a few questions once and for all.

I can 100% confirm that the bearing sits in oil (after my man forgot to drain it). As soon as he undid a cover plate bolt, the oil started to pour out :grin:

^^^^^ Thanks Chris - top man!

And make sure there is not a customers car close by when you take the IMS cover off if you haven`t drained the oil :floor:

Great work that man, I've often wondered where the oil levels came to inside the case at max and min on the dipstick. Like you I always keep the oil level topped right up :thumb:

:thumb:

I used to work in cleanrooms (for Philips manufacturing CRT cathodes - 500,000/day), which meant dry bearings on all the equipment. Due to them all being frictionless bearings (like the ims bearing) it was possible running 24/7 and they lasted for months. Folk don't realise these type of bearings only need a bare minimum splash of oil to make them last foreve (unlike solid bearings). Don't know what Porsche were thinking putting a sealed bearing in an oil bath :?

Having looked at a few dismantled M96 engines at my indy's place, doesn't the real problem lie with the narrow width of the connecting shaft that inputs into the IMSB. That shaft ought to have been thicker. Then when a bearing fails as some always will (it's a part so some will break) the shaft won't break and cause havoc as happens commonly now. Sure bits of disintegrated ball bearings floating around are never good, but at least all the connected bits would still be, er connected until repair? Surely it's in the lack of designed in inevitable failure where the design went wrong? And that's not something that arises from cost cutting. That's from bad judgement and incompetence. If the Harris case had pushed that angle more Porsche would've had a real global problem I think. Having read the papers from that case I often wondered if it was a fear of that angle of attack that made them settle so easily :dont know:

It's not the bits from the bearing floating round the engine that do all the damage (although they'll do some). Once anything breaks with regards to the ims, it throws the cam timing out, which then leads to overcrowded boxing match between 6 pistons and 24 valves (imagine the carnage after that). I must admit, I was quite surprised at size of the spigot that supports the bearing . The undercut at the end of the thread must only be in the region of 8-9mm in diameter, supporting a large shaft with 5 chains running 4 cams off it. :nooo:

Exactly. That's my point. (I abbreviated the above to 'connected'!) The width of that shaft would have been discussed I'm quite sure with regard to acting as a fail safe for the inevitable failure of the bearing (at some point). Someone either decided that the failure would be so rare that it wouldn't matter, or to ignore that additional level of fall back. The width of the shaft could easily have been doubled in size. So why wasn't it? That's the question I suspect Porsche don't want asked. It's a bit like the water cooling flaw in the larger bore engines. Surely someone asked questions internally? :?:

The shaft I have from Hartech is a lot thicker than standard and I recommend getting it changed if you change the bearing. The standard one can get weakened by removing the cover and re-tightening, it's still a known weak point, sometimes overlooked.

I would've deffo done that if I was removing the bearing. The fact that OPC scored all the seal on one side of the plate refitting it put the frighteners on me. I'd probably make my own if I did one with something like an M18 thread on with no undercut.

Do you think the mileage estimates on bearing failure probabilities vary much with age, and if so how? Surely a car that does 50k over say 4 years will have a very different effect on the grease displacement etc that one that does 50k over say 10 years + ?

Infant mortality - nuff said. https://en.wikipedia.org/wiki/Bathtub_curve

The view of Road & Track Magazine. More odd 'stuff' on the IMSB - e.g. "a short run of low capacity bearings, 'some' of which ended up in early 996's." "The biggest reason for low 996 values is the misconception that the engines have the durability of blown glass. This is one gripe with the 996 that really needs to be addressed. Some early cars featured a weak bearing in the intermediate shaft, known as the IMS. Porsche has used an IMS in its 2.0-liter engines since 1965. The IMS drives the camshafts indirectly off the crankshaft. But even before the introduction of the 996, Porsche had experimented with new bearing designs, and this development resulted in a short run of low-capacity bearings, some of which ended up in early 996's. An IMS bearing failure results in a completely destroyed engine. Luckily, most qualified Porsche shops can perform a pre-purchase inspection and identify bearings that have been upgraded or may need to be replaced. As terrible as a blown engine is, enthusiasts have made it seem like every 996 came with a defective engine. Further fanning the flames, Porsche's handling of the problem was a PR disaster. But the reality is that the majority of the engines are fine. "Engine failures in [engine model] M96 in actual real numbers range from one to five percent," Brownell says. "It's more than there really should be, but it's not quite as dire a situation as the Internet would have you believe." What's more, the problem can be corrected by a $400-$700 upgrade."

Don't believe everything you read - this comment is blatantly untrue. Just goes to show journalists are not mechanics. The only way to identify anything with the ims bearing is to remove the gearbox and strip the cover plate off. No ppi will do this. :nooo:

I agree with the first and last part of this statement. The middle bit not so much. It doesn't 'show' anything. Some of the technical details are not right in the 'Road and Track' article, but some of the rest of the judgement, thinking and advice in it is spot on IMHO. Technicians have greater tacit knowledge, sure, but being human they're just as prone to bias and judgement errors when dealing with matters like IMSB. So while they may be more technically accurate they will still need treated with scepticism as they can be written with all sorts of unconscious biases influencing thier views. Most will are either defending an opinion or selling an idea. And that isn't being disrespectful to mechanics or engineers. But just like economists, historians or any profession, get 10 in a room regarding complex matters like 'bore score' or 'IMSB' and you'll get 11 different answers. Baz from Hartech is the closest I've seen yet to someone in this debate who's not just put in the work, but also the method and systems to support better judgement to base his claims on. That's why there can be greater confidence in what he posts, IMHO. And it's why I disagree with the binary and frankly simplistic assertion that because mechanics or technicians have experience they're therefore 'right' and journalists are always 'wrong'. When it comes to complex matters each needs handled with care.

Point I was getting at Paul is people read these articles and think that it's the gospel truth when in fact it's more a case of the author (for whatever reason) not understanding what he is writing about and has more likely got bore scope checks for scored bores mixed in with his comment about checking the ims bearing on a ppi. It's a real shame as some potential purchasers may think it's ok, if I get a ppi done, then the ims bearing will be fine, when both you & I know that is far from the case. There's more truth in you favourite rag - the 'Daily Fail' :lol: :thumb:

No specialist Indy that I'm aware of (including all of them) will tell you the ims bearing can be checked on a ppi.

There may be documentary evidence in the for of a receipt/invoice if it's been changed or looked at during clutch replacement. But here is another dynamic.......... What if there is a receipt to say it's been changed - would you take comfort if it was an LN one? What if it's been done and a standard bearing has been fitted with a hammer?. :dont know: Personally I think it might be preferable if one has not been changed which then gives you the options being discussed in this thread.

All I wanted to see in my bills & receipts before any dosh was parted with was: Mobil 1 Mobil 1 Mobil 1 Mobil 1 Mobil 1 Mobil 1 At the time though, I was very naive to the 996 and would've welcomed a bill that said ims bearing upgraded, even though OPC won't ever do this job (as far as I'm aware).

Comes as an 'assembly' - AKA replacement engine!.

Thing is even the most sorted and mint 996.1 is still only going to be a £12-15k motor. If anyone was worried they could get a full Hartech strip and rebuild for £12-14k. That's still an appreciation proof icon you can use everyday. All this fear/prejudice is keeping us 996 owners out of the self regard threads of the air-cooled world. But at least it's keeping 911 motoring accessible :dont know:

Or you could buy one of these little components and pop it in! http://www.ebay.com/itm/Porsche-996...ash=item33aed50474:g:~EsAAOSwcOFWbg2c&vxp=mtr I wish! Seriously though, I never expected the thread to go so deep. And I'm actually still pretty unsure about it all. It's a bit like one step forwards two steps back. You think you've gotten to a point of resolution and then another angle or nuance appears from somewhere. I know Baz is held in very high esteem here and I don't question that. Thumbs up for Baz and Hartech. But for someone of my limited technical knowledge, he's just too far out there for me. I realy struggle to get a definitive layman's understanding from his posts as they tend to be very long and full of all sorts of mechanical and engineering concepts, theories and phrases. A delight for engineers and the mechanically savvy DIY'ers no doubt. But not for me and I suspect a few others of the no idea what's going on under the hood brigade. It's a bit like asking the top speed of the car and getting all sorts of potentialities and variables regarding angle of road surface, resistance of rad surface, density of traffic, wind resistance and latent atmospheric temperature measurables! I just want to know the top trump answer, 174mph. (Give or take). I would love to see someone more capable than me pull it al together in a sort of sticky thread, one that has real consensus and then leave it there once and for all. I've learnt some thinks in this thread and have become a lot more aware of the general discussion about what the best option for owners which is the real point of this thread. So there are different needs for different eras. The right option for a 3.4 dual row bearing owner is not necessarily the same course of action that a 997 'big bearing' owner would be looking at. Yet the IMSB discussion tends to lump them all together. I think what I'd love to see is a sort of universally agreed excel sheet with the different engine formats, 3.4 (1), 3.4 (2 -if there was a change), 3.6.1, 3.6.2 (if there was a change), 997.1, 997.2 and a sort of drop down micro menu that says something like (and I'm making this up for the sake of argument). 3.4.1 Dual Row Bearing. 98% reliable. no need for random check until 140K miles. Remove dust shield. Change oil every 5K miles. Check with clutch change, replace with new bigger single row (Porsche Standard Part). unless it's clearly still perfect.Stay away from x,y,z... 3.6.1 Single Row. 90% reliable. Need to check before 90K. Unless perfect, change to large Single Row (Porsche standard part). Change oil every 5K.Stay away from x,y,z.... 3.6.2 (is this the 997.1?) IMSB is locked inside casing.You're options are x,y,z.. Stay away from x,y,z... In fact a little app would be cool but a definitive sticky thread would do! All endorsed by the likes of Hartech, Autofarm and whoever else who does this type of remedial or preventative work..... And then, the idea is that it's all out there. Everyone sees the real transparent simplified version of it and knows exactly where they stand and what they need to do, what they should do and what they shouldn't do. And I think when we get to that point, the engine issue with 996's will be over once and for all and the world can start to talk about how brilliant the car actually is and always has been. So I'm happy for the real egg heads on here to bang heads with the techno wizards at Hartech and whomever, and create the definitive one pager and I'll keep asking stupid questions whenever the lingo gets a bit techie. In actual fact, if people had more confidence in terms of the best course of action, owners would be much more likely to spend a few bob and get stuff done. I think what inhibits a lot of is is not wanting to get caught up in the 'apparent' snake oil sales pitch.

For me (as somebody with reasonable technical comprehension) it is not hugely complicated but I understand how it could be. I doubt you will get that level of 'definitives' due to a few reasons:- Manufacturers really keep detailed build history so where changes occurred in respect of a vehicle run would be difficult to pin down to a range of engine numbers. Sometimes manufacturers source the same parts from different sources so it might be that the issue is with one supplier not all suppliers. Nobody will be brave enough to give a definitive mileage other than a gut feeling from sales they have worked on (Baz already has done). It's a free market - snake oil salesmen love free markets!.... Cars break, $hit happens.

To help people understand a little more, I usually post pictures from my previous rebuilds, I think this helps to get a better idea of what is being talked about.

You know, it's not that I'm worried about my car. It's only at 80K miles and has a long way to go before it'll need big work by which time I'll be delighted to do a lovely shiny new engine rebuild/refresh. Can't wait! My initial motivation at the beginning of of the thread was seeing the DOF video and thinking, hey, why not, that looks like a good thing. I'll just pop into 911Uk and get a sense check, maybe someone has got it done etc. But I think as the thread has progressed my motivation has changed. There is so much contradiction and confusion out there (as evidenced by top magazines pumping out alternative myths) that it's the contradictions and myths that are the real problem, not the bloody bearing So I'm now on a bit of a mission now to get to the bottom of it all for the sake of clarity, somehow, someday and hopefully we'll see the end of the IMS threads! Just to give one example of an ongoing prevailing contradiction. There are at least five distinct versions of the IMS bearing core problem itself that I can make out. There is: A) One off random batch of bad ones theory. Luck of the draw. (Road & Track et al). B) Theory that the bearing itself wan't built strong enough. (Porsche's own theory apparently). C) Theory that the bearing is perfectly good but it's not lubricated properly. (DOF theory, dust shields, etc). D) Manufacturing variance theory. Not so much a bad batch but just a sort of one in every hundred IMSB's comes off the production line somewhat less than perfect (in which way no one knows though). E) Random theoretical combination of all three above. ie. No one knows theory. (New bearings, DOF, how you drive, how you start the car, which brand of oil you use, anything and everything kitchen sink theory etc etc etc...) (Or, in some cars it's a bd batch issue, in others its how you drive, in others its poor lubrication and so on) Each of the theories raises all sorts of secondary issues. The right fix for one can be the wrong fix for another. Or each has separate conflicting implications. If we could even get agreement on just this one thing alone it would solve 90% of the whole IMSB saga! Bad batch or bad bearing or bad lubrication? With all the dozens of posts and threads and magazine articles I've seen, I keep coming across different variables on this theme. You would think by now it would be well an truly nailed. Did the US class action specify what the core issue was by any chance? If I was to proffer an uneducated guess I would say that I'm not convinced by the lubrication thing because all cars are essentially the same so they'd have all failed. Bearings would be failing right left and centre. I'm not convinced by the production variance because it's not that complicated a component. I can't imagine there being any real difference between every twentieth bearing and the rest. I'm not convinced by the bearing was never designed correctly in the first place. Seeing at 90-95% of cars have worked perfectly well it seems the design was fine. Maybe the bad batch theory makes most sense then. A bunch of engines popped and that's basically it now? In which case any decent replacement is a good option. I don't know!

Do Hartech supply the whole shaft and bearing thingy to anyone or do they only install it themselves? Sounds like an interesting option during a clutch change. Have you ever heard anyone express a downside to it?

I gave them my IMS and they fitted the bearing and shaft, I just refitted the whole assembly into the crankcases.

Had the car up on a ramp over the weekend so checked and changed the oil filter for any signs of particles. At first it looked like there were but then realised was just a few small bubbles. Had a thorough look through and nothing in there at all. :wink:

Could we sticky this thread? It's got mega information in it.

Or misinformation!

Repeating my request to sticky this post......too useful to waste!

Agreed MODS can someone please sticky this thread as it's one of the best reads re this subject on the internet. And this subject is one one the most emotive regarding these cars. :thumb:

I'm not sure what the thread ultimately delivered though. I've seen the latest issue of Porsche and 911world and they have apparently just done a three issue spread on the M96/97. This is a top magazines most concerted effort yet to get clarity I would imagine. I only got the third installment which includes a sort of round up of everyone and anyone in the M96/97 game and their various 'solutions.' So you flip over the page after they do their final round up and what do you see? After all the analysis, deep investigation and lengthy conversation with the 'top people in the industry,' you see a half page advert from L&N with the statement 'Fact; the IMSB is semi submerged in oil. Oil is not the problem - it's the bearing.' Right across on the opposite page is another half page DOF advert with a big statement, 'it's not the bearing, it's the oil feed,' and also on that same double page advert spread is a half page advert from Hartech who from what I can interpret and extrapolate out of their lengthy posts don't have much time for either of the two so called solutions advertised next to their own advert. Yet Hartech are mentioned as prime consultants for the article - how frustrating must that be! It's all just a bit absurd at this point, descending into the realms of ludicrous comedy that a magazine does what appears to be such a huge investigation and yet ultimately end up with the key players still at complete odds to each other, all featured in the same summary article. And of course, all the time, the great elephant in the room, the ongoing borderline criminal silence from Porsche themselves. Who seem to have absolutely nothing whatsoever to contribute or ever have. I think it's time for a 911uk open letter to Porsche to be honest.

This thread is being reviewed by the Mods team/ 911uk admin.

I think the key is in the above. Hard to navigate through all the promotion. Starts to sound of "Sea Monkeys" and "penile enlargement"

Problem with magazines is it's hard to tell whether the supposed article is genuinely a fact based unbiased investigation or a sales led and advertiser funded advert hiding behind the guise of investigative journalism . These mags are all about sales and ads and of course if that was the case the stories would be very biased recommending the advertisers and suggesting the fixes were done and would be wooley and inconclusive. It seems highly suspicious to me that there are huge half page ads from the companies involved who clearly don't have it in there commercial interest for there to be a cheap easy solution ,and it really doesn't sound like an unbiased representative article. So I for one will be treating it as the advertiser focused sales campaign that it appears to be and will be taking it with a large pinch of salt. :bandit:

Thanks for stickying this, mods :thumb: :thumb: I'd far sooner believe this thread than a magazine article, as the guys say above.

I'll tell you where I stand on this today. It's a bit of a 'if you can't beat them, join them' scenario really. I remember when the green movement was beginning to get quite significant, watching the CEO of a very large global company saying on TV, 'Look, I have no idea if it's true or not, but if our customers think its true then we have to go along with it. Simple.' There are certain realities at play when it comes to IMS. Porsche will probably never ever comment let alone do anything remotely consumer centric like provide a cost effective (or free - Lol!) approved Porsche solution. Certain magazines will continue to cut and paste material regardless of whether it's been long disproven or not. They're not investigative journalists or engineer'.s I don't particularly blame them. They're in the same boat as the rest of us. The market for M96/97 preventative work is pretty significant. 150K cars or so! It's pretty lucrative and a number of companies will seek market share in that space, with various 'solutions.' So for many years to come, there is going to be a continuous marketing campaign in the magazines and on the net to drive market share of the various M96/97 preventative /cures'. And when every single IMS bearing has been replaced along with a Direct Oil Feed added and IMS Guardian's installed etc. etc., and the market has dried up, they'll all suddenly be due a 're-replacement' at 40k miles for about a grand or your engine will implode. So the white noise and cacophony is not going to go away. 996/7 buyers guides will be a quarterly regular on Total911 for years to come. Myths and solutions will be recirculated time and time again as new buyers enter the market continuously. New videos will emerge on You Tube by new engineering companies keen to get a piece of the action, in a market where a 10euro bearing can sell for 900euro. We're talking Hermes type margins here. All facilitated by the vacuum created by the cynical cronies at Porsche A.G. And what magazine journalist is ever going to doorstep one of the continuous line of PR men and PR 'engineers' sent to them to promote the latest PR stunt/Halo model (that is already sold out). Not one because that'll be the end of their cosy relationship and invites to drives these cars. I have yet to come across one single instance of a Porsche magazine journalist asking one single Porsche representative in print or on video about the issue in spite of the fact hat their busy printing about three articles a year on it. FFS! So ultimately, and I see it happening already, every 996 owner is going to have to get it done if they want to sell their car onwards at it's real value. The question will be routine - 'have you have the bearing done mate?' Until someone wins a legal case against one of the 'solution' suppliers whose product fails or wins a case against a magazine pushing a certain products that subsequently fail, the world at large has bought into it and it is therefore de facto the same as having to have a decent set of tyres on your car when your selling , or cleaning it!. So if you're getting that clutch changed, you might as well get that IMS box ticked regardless of whether you believe in L&N's bearing or whomever's or not. Whether you need it or not doesn't matter. You may well come to sell the car before the next clutch job and you're guaranteed to get the 'what's the story with the bearing mate? question. The tidal wave of marketing cannot be withstood. Fear marketing is the oldest version in the book. In fact epitomized by L&N's now infamous advertising 'pop, pop bang!' campaign. So, suck it up, and pop it in!

I haven't time to read back through this whole contribution wither - and we haven't posted on this subject for a while because everyone seems to be getting the message - but I think to repeat our post of Dec 2015 achieves two things - firstly that not every specialist exploits concern to make exaggerated claims and secondly that the power of Internet Forums eventually allows a message to get across - amply described in the last post. Just one additional statement I would like to convey and reinforce is that is that the larger IMS bearing in the later cars really is a solid reliable solution (especially with the outer seal removed). In the years ahead many engines will need a rebuild anyway and it usually costs little different to wait for an early bearing to fail (or a liner to score or crack) and rebuild it with the best solution and may prove a better investment than trying to avoid the IMS bearing failure only to find the solution chosen didn't last that long or something else failed to require a rebuild anyway when the most reliable solution could be incorporated at the same time. This is a relevant extract of what we posted last year:- We are not only aware of all the types mentioned (thanks) but have seen most of them having failed. The lateral loads on the IMS are not established but a ball bearing is designed to work both ways and with a splash oil supply and we have had discussions with a lifetime bearing manufacturing executive (who happened to spend a lot of time researching all the options and available bearings and owns a Boxster S) and he agreed that he thought it would need something better than a flat roller bearing end face (unless it also had a pressure oil feed) - but no one will have tested enough to destruction to confirm or deny anything - except that we receive and repair 4 to 5 engines/week (which has increased from around 2 to 3/week a few years ago) and I think the feedback this provides about the condition of original bearings, worn bearings and different IMS kits combined with our basic engineering knowledge is about as good a clue as to what the true situation is that anyone could provide. You may remember (or can check back and find) that we were very unimpressed with a idea of a ceramic type many years ago (before they were in general use and known to fail) and have had two in here having failed in the last few weeks - I seem to remember we suggested they would be no better than the cheaper std bearing (possible worse?). But you must appreciate (as we do) those specialists that try and provide solutions for problems that the manufacturer should have sorted out for their customers first. Usually spending money to genuinely try and find excellent solutions (and I do think they are more motivated by a belief in the success of their product and how it will help owners than doing it purely for commercial rewards) - but if the main manufacturer with a superb reputation can get it wrong - it is expecting a lot for most general technician specialists to find a better solution on much more limited funds in with far less test opportunities and resources. So I prefer not to knock those that don't always get it right while being frank about the difficulties some problems create that are often almost impossible to improve without huge expense and modifications. The IMS bearing is a difficult problem to improve on in the space available without huge cost while the larger ball bearing seems (from all feedback and experience) to be totally reliable (and is available). What to do will unfortunately always be a gamble and it is the odds that should influence decision making. Unless there is an obvious reason to get into the smaller bearing in situ - I suggest it is a better bet to ignore it (or take the seal out if you are close by with the flywheel off and know what to do so you don't loose cam timing and can replace the outer carrier without straining the weak spindle). If you were lucky enough to find the bearing damaged but having spread no debris anywhere - it must be worth carefully replacing the bearing and spindle. We are reluctant to retail our replacement bearing, spacer and spindle kit because we suspect some owners will damage their engines trying to fit it (or have a premature failure later) but we will do so ourselves if requested - but without our usual cast iron guarantees. There are plenty of others now with their own kits that are prepared to fit them for their customers. I think this whole range of cars are really superb - among the very best cars (on the whole) that Porsche ever produced and far less expensive than they would have been if the engines were more reliable - in fact - looked at in numbers - they represent superb buys with relatively little risk - and if you are unfortunate enough to suffer a failure - it is not too expensive to not only repair it but also improve those weak areas to result in an even better car that will appreciate in value. It would seem to me to be a great shame to spend a lot on an apparent IMS "upgrade" only to find that later the engine needs rebuilding anyway and could have then been fitted with a much better solution for little more cost at the same time. You must make allowances when I offer replies that sometimes I am referring to a theoretical issue someone has raised, or countering an incorrect technical conclusion or opinion and not always discussing what to do. Unfortunately there is no good easy reliable permanent answer to the IMS small bearing issue without stripping and rebuilding the engine but plenty of good reliable and affordable "upgrades" if the engine is apart - as long as you also avoid those issues where some specialists do (probably out of ignorance or greed) promote a solution that has been proven to be short lived and often results in an engine requiring a second rebuild shortly after the first. END OF REPEAT! I think the above shows that we at least didn't try and exploit the situation and did try and provide well researched answers and that despite the often used accusations of "scare mongering" plodding on with accurate responses eventually achieves some understanding for readers that is useful to all. The original double row bearing created more running in metallic particles to mix with the remaining grease and often lead to premature failure - but if they survived that and the seal was worn to allow oil to enter (as most remaining are old enough now to be) they often then managed to last very well and as most early failures were covered by warranties this may have influenced statistics taken later that mask the true picture. Baz

https://www.youtube.com/watch?v=IxdvSq_byZw Interesting little video and comments!

"hybrid ceramic bearings are superior in every way and they don't really have any disadvantage over regular steel ball bearings" This guy is not an engineer.

+1.

picture of the larger type IMS bearing and housing

Great information here, thanks :thumbs: Ok.. so I can remove the 3 bolted cover, look inside and see the bearing and seal. If I were to pull that seal off, (call it the outer) I'd then see the bearings in their case. On the far side of the bearings there is another seal (call it the inner). I can't see much point in just taking off the outer seal - where is the benefit? Surely it's the inner seal that is key if I wanted to get more oil in the bearing. Is it possible to get a small drill (by hand) between the bearings/case and puncture the inner plastic seal in several places? I have no idea what bearing is in my C4 (100k miles 3.4 2000) but am planning a clutch replacement soon so should do something whilst it's accessible.

I think maybe you should re-read the thread. What do you suppose are the effects of removing that seal... (Considering the bearing is surrounded by lots of oil and a large ims chain drive gear) :?

And where would the swarf go from drilling holes in the rear seal, if you could get a drill bit past the bearing cage in the first place.

Just as a initial comment, I'd strip the seals off a new one and exchange them, rather than just strip an existing IMSB - you've done the hard work and or expense to get here, no point in not fitting a brand new IMSB! (circa £70) Anyway, back to you methodology description, yes you can pull the "outer" seal without removing the IMSB, but the engine oil you want access to is on the inner face, and drilling holes is not possible on dual-row any way due to the two offset twin-races (and although possible on single-row, you would be mental to attempt as you could damage IMSB and certainly create debris the other side of the inner seal to be swept around the IMS, IMSB and engine in general), I suspect the drilling idea would not even be very effective in oil flow terms either. Just pull the IMSB (takes a few seconds) and either strip both seals completely, or ideally fit brand new IMSB with both seals stripped. Here are a couple of YouTube vids to show how pointless the drilling idea would be:

I would be a little more cautious than that. This bearing provides the end float to position the whole shaft and chain. As you remove the three holed carrier it pulls the IMS towards you and bends the chains. When the carrier is far enough out to slip off the end of its larger diameter to become loose - the chains both pull the shaft out of the centre line and this can lead to them jumping a tooth and miss-aligning the cam timing. Undoing the two tensioners can help (one for crank to IMS and one for IMS to camshafts), but any movement of the shaft can pull the chains and they have been used to running on plastic runners and will have created some grooves by now that the sideways movement can chip if you are unlucky or damage the chain link side plates that are brittle and can initiate a fatigue crack later or pin failure. When you come to replacing the "spider" (the three bolted end plate) you find that it starts to fit the large diameter into the crankcase hole at the very same time the shoulder on the centre shaft runs up against its own shoulder and it is very difficult to pull the centre of the s haft over far enough to get both to engage at the same time and without losing the cam timing. The standard spindle has a recces in the centre to hold an "O" ring that makes it very weak in bending and while trying to push it over far enough to get the parts to line up you apply side loads that could create a crack initiation and eventual fatigue failure. Finally the outer spider seal is designed for assembly during 2 halves of the casing shutting together and not sliding into a hole. If you were also changing the bearing you can remove the old one with a slide hammer (but then need a support to align the shaft so it remains in the right position while you are removing it). The old bearing had a sprung clip best removed with a shock from a sliding hammer but the later circlip retention can allow a puller to remove the bearing. Using a puller with the old sprung clip can sometimes result in it becoming entrapped and damage the clip groove = engine rebuild. There is no benefit whatsoever in removing the inner seal - the oil feed is from the outside and inside is just a tube partly full of old oil. If you remove it you need to remove the bearing with the associated problems mentioned above. However if fitting a new bearing it makes little difference if you do or do not also retain an inner seal. This is all good reason to be reluctant to carry out this work (although we will and do so when our customers request it). One of the problems for us is that - imagine that by bad luck a chain or tensioner runner broke some time after fitting a new bearing - who is then responsible for a whole engine rebuild to fix it and all the new gaskets seals and lubricants that are essential? With experience, tools and care failures would be extremely rare and probably the majority of "home mechanics" would be lucky and get away with doing it themselves - but it would just take one failure for a business to regret doing it - because you would need to successfully carry out hundreds of similar repairs to cover the cost of just one going wrong resulting in a full rebuild! With experience, some special tooling and familiarity with the job - specialists usually carry it out very well but for a one off first time without special tools - I would be very wary indeed. There are plenty of specialists happy and experienced at this job and I would recommend you find one happy to do it for you rather than struggle yourself. Good luck anyway. Baz p.s. before there are complaints about my long answers - just try the job yourself and then feel free to comment.

On the basis I would to prefer an old and presumably worn (possibly critically) IMSB to be replaced with a new IMSB, I would strip both seals prior to fitting (it makes no sense not to). In terms of the space behind the IMSB, every extra bit of "headroom" would improve the prospects of genuine turbulent IMSB wash. For general reference, here is photo of single-row ex seals: And although my previous description may have sounded off the cuff, I do agree the mod is NOT for the DIYer to attempt (not least the cost of the proper tools required for insertion and correct refit outweigh the labour savings) If time was of the essence, then yes, only pulling the outer seal is better than pulling no seals!

If the non-specialist press can get it right, why can't the Porsche press get it right? https://www.pistonheads.com/feature...rsche-boxster-986--ph-used-buying-guide/37360

What a thread! I've been away from Porsche for a while but the car still waits patiently for use and attention. That time has now arrived. My IMS bearing was inspected when my clutch was done @ 15 - 20k miles ago (cars on 85k now) when the IMS cover was changed. The local and trusted Indie said it was fine. After reading this thread end to end - and I did, sort of puts things into perspective mostly the input from Baz. My view is if it reaches 100K then anything after that is a bonus and a rebuild is due anyway due to natural wear and tear. No guesses for where I would have the unit rebuilt. Baz's statement should go down in Porsche history. It's been a few years since I drove the car, now where's the rear window washer switch?

So i got a 99 3.4 which will have double row its at 72000 miles ... So its going to blow up or not ? How much to get a independent to pull off front dust cover ?

If its a manual wait till you have a clutch change. Should only be an hour or so on top.

While this thread has been resurrected I thought it a good place to mention something I saw over the weekend on the Porsche stand at the Festival of Porsche. Among all the Drivers Selection clothing and usual tat, they had a short engine M96 on show, I was obviously curious as this is my kind of thing. When looking at the IMSB I noticed that this genuine supplied short block had some kind of uprated IMS. The bearing post is the same thicker type as the Hartech one that is in mine and the nut, that was fairly basic before is now a lot larger and is a flange nut spreading over most of the bearing cover face. I wonder if this is the larger bearing too?

Did you not strip it down and have a look?

Dam , Infra how do we find out , I now want to know if Porsche have fixed a problem they wouldnt admit they had and if the uprated part is available to buy seperatly :dont know: and if so how does the price compare with the known aftermarket fixes :?:

My car has a 2010 manufactured 3.4 engine, this has the non serviceable style last design IMS so they have incorporate changes into replacement engines.

For a visual comparison to Infrasilver's post, here is my original MY99 3.4 IMS bearing cover: The nut and centre is much larger. The case halves casting is different. But the hole the bearing fits in looks the same size. Looks to me like they decided the centre pin is the thing that needed beefing up. A bearing with a larger centre with the same size outer means the balls are smaller.

The bearing doesn't fit through the hole on the final design. Hence why the engine has to be split to fit one.

Think someone posted a while back that all 'new' 996 engines (including the short blocks) had the revised design in.

The thicker centre pin is something I have had in mine for around 5 years, fitted by Hartech and the IMS cover hole is the same diameter for both but the thinner bearing post is only thinner where it has the waisted section for the O ring and the threads, this is also the weak point of the original design. The centre of the bearing stays the same diameter ie you can use both posts, thinner original and thicker upgrade with the original bearing. With the thicker post you don't have room for an O ring though. If you hear what sounds like metal in a washing machine (think roulette wheel), the end of the post has snapped off with the nut, shut off immediately.

I am probably going to change my clutch as my 2019 maintenance schedule to keep the car top notch. I currently drive a 1999 (nov) with 80k miles. What is the current "best in class" consensus replacement for the IMS? Direct oil feed? LN or Flat six or something else? I know well worth doing the RMS at the same time. Are people pro-actively looking into flywheel when replacing the clutch? Lastly if I may what is the view on the low temperature thermostat? I have seen my car had the oil separator replaced in 2017 so not needed at this point. I had also read people changing the water pump when doing this bigger service, saves much labour time? Still love the car every minute, thanks all

The best option on a '99 3.4 C4 is to remove the outer seal from the bearing fitted. You can check if there is any play in the bearing but I doubt there will be. Once the seal is removed, bolt back together, let fresh engine oil lubricate the bearing and forget about it. Any after market alternative bearing that fits your ims is no better than what you currently have.......some may say any after-market is inferior.

Leave the RMS alone if it's not leaking........and personally I wouldn't bother with a LTT on a 3.4, only the bigger engines that score bores.

IMHO: 1) Is the clutch slipping or noisy? no need to change otherwise... 2) Best thing to do with the IMS bearing is leave it in place, flip the outer seal off so a bit of oil can flow through it. The 3.4 has a minuscule failure rate compared to the 3.6's small failure rate. Leave the RMS alone unless leaking. 3) I replaced my flywheel as it was grooved and felt a bit loose but still passed the test. Yours is likely fine at just 80k. 4) LTT is more important for a 3.6 where reduced temps can help stave off bore scoring, a 3.4 is more durable so I think its not necessary. That said it will not do any harm apart from slight increase in fuel consumption - I run one. 5) Water pump is probably a good shout at that mileage if never done before, to save it going at an inconvenient time. At 80k and 20yrs it is an old engine, there loads of things that could go wrong, no point in addressing just the IMS Bearing when the 3.4 has a very very low rate of failure, and there is a risk of damage when replacing it in situ. Check my thread linked in my sig for pics of what is involved for most of this work.

Another "Uprated" IMS bearing fails. Ceramic one apparently. https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/173916170973 Am I right in thinking that the new thoughts surrounding failed IMS bearings has a bit to do with tolerances being too tight or even misaligned slightly at the factory?

Some slight misinformation here, the 3.4L engine with dual row and KS pistons has a significantly lower failure rate of bore scoring and IMS failure than the 3.6L engine with the Mahle pistons and single row bearing. But there are 3.4L engines at the end of the production run of the 3.4L with single row IMS and Mahle pistons which makes this engine just as vulnerable as the 3.6L to both failures. When Porsche switched isn't exactly clear but for sure if your engine was made in the 90s it has the more robust parts, but its over 20 years old and that in itself is an issue too, so can't do right from wrong when buying one of these cars. The factory press fit of the IMS bearing has a lot to do with it's life expectancy too as the outer race can be deformed on a tightly fit bearing, as well as how often the car has been used or sat around in bad oil, how often its oil has been changed and just down right luck. Chain whip also has a big part to play in this story and it seems the dual row tolerates this better as the load carrying capacity of the dual row is actually slightly lower than the single row believe it or not. Removal of the bearing and replacement of it runs a risk of damage to the chain guides by moving the location of the chain slightly so yes removal of the seal on a healthy bearing is a good thing as it allows better lubrication to the moving parts of the bearing and this is never a negative thing. But when you engage your brain a bit you'll realise they're all going to need a rebuild one day, so if it's working fine just enjoy it and think about rebuilding the motor one day. Because there's a lot a good specialist can do to really improve these motors.

Good post DarthFaker (been reading our report on IMS bearings?). Anyone interested its available from [email removed] - a long read but covers everything relevant. Baz

:grin:

Great thread! I'm about to replace my bearing as I had some silver sparkles in the oil filter. The gearbox is removed and I'm about to order a bearing. My first thought was to source a new original type bearing and remove the outer seal. Cheap and it looks like consensus is that it will last a long time. Then I stumbled upon this: http://shop.guldenbergracing.nl/996/ims-lager/guldenberg-hydrostatic-ims-bearing It would be nice to hear opinions about this kit even though I guess no one has heard about it. It looks like a cross between DOF and IMS Solution. It lacks a IMS plug and spin on filter and the oil feed point is the same as DOF, otherwise it looks like a IMS Solution. Cheaper than IMS solution but more expensive than DOF. Thoughts?

Hi Looks like a great bit of kit, but I like your original solution better as long as you can get the old bearing out and in without causing any damage and correctly aligned. All the best Berni

How do you know it's the ims bearing that's created the metal in the filter>

I don't know where the metal comes from. However as I have a 2000 996 I don't even know if the car has a single or double row bearing. So I removed the gearbox and while I'm there I'll look at the bearing. And if I have come that far I guess I can replace it with a new bearing even if it looks ok, I must remove to find out what condition it is in. Then I can drive a few kilometres and check the filter again to see if it has improved anything. If I find more metal I will look for other sources. That is my thoughts and plans, I'm already halfway there. A cheap new original bearing is a small investment to rule out the IMS bearing as the source of the tiny metal flakes. I'd like an IMS Solution but I find it too expensive.

Ping the outer seal off the bearing and leave it be. You can check the condition without removing it......and you can do more damage removing it. It will be dual row and most likely mint. Save your dosh for fixing all the 2pyr old rotten stuff like seized bolts and failed sensors.

:yeah: MC

Thanks, I guess that would be a good choice for many but if I do that I still haven't ruled out anything and would still have something shaving metal flakes into the engine. Most of the other possible sources would require the engine to be removed and disassembled. I believe that makes replacing the bearing a well founded and rather cheap decision even if there is a possible risk that I screw something up. A new bearing in place would in my opinion be better than an old possible faulty one. As to checking the condition of the bearing with it still in its place I thought some bearings could look fine until you remove it and examine it more thoroughly.

Replies recently read as if some new readers have jumped into the most recent posts and I think they would benefit from reading the whole post from the beginning as it already answers many of the points they are making assumptions about. Baz

You inspect the bearing by feeling for any play in the centre spindle. Also turn it by hand and try to stop the bearing cage from turning. If you can't its perfect. If you fit a new bearing and its tight due to manufacturing tolerances, it could prematurely wear. SERIOUSLY - STICK WITH WHAT YOU'VE GOT IF THE INSPECTION OF IT PROVES FINE!

Hi All Am also about to check my IMS (and remove the bearing cover). I will lock the crank and also the cam (on drivers side - using a tool from Alex!) before I loosen chain tensionser. Had a couple of questions: 1) I assume I will need a new IMS seal (ie you dont reuse the old seal) - if so does anyone know the part number (2002 C2)? 2) Do I need new tensioner seals (O-rings) & washers? 3) Do I need a new O-ring for the IMS shaft (I believe 7mm x 2mm). 4) What thread sealant do people use (for the 3 bolts on the IMS spider) Just trying to work out what I need to order in advance of doing the job... Thanks!!!!

1, 2 & 3 can be re-used so long as they're not damaged. ie. leaking before you start the job.

Thanks Alex..... I did a load of research last night - in case anyone needs the part numbers: IMS seal- seems its the same for all M96 996 (part number 996 105 112 01) IMS Shaft O-ring - 99970739240 Until I get in there, I wont know if its IMS or RMS thats leaking. So will hold off on ordering bits....

IMS strategy? This is a great thread that I've read from start to finish and contains some brilliant insight from knowledgeable owners. So I've just bought a 1998 C2 996 3.4 Tiptronic Coupe with what certainly appears to be a genuine 34k miles. The service history is reasonable. My question is what is a reasonable strategy regarding the IMS? I understand that the failure rate is significantly overstated but I'm mechanically qualified and want to do everything possible to research its state and protect for the future if possible. Is this logical? 1, Can I assume that it probably a double row at this build age? 2, Is this the bearing most likely to be reliable? 3, I'm tempted to do an immediate oil and filter change and have Miller sample the oil? Worthwhile? 4, If the sample comes back metal free would it be considered sensible to remove the Tiptronic and remove the IMS bearing outer seal? 5, If 4 is a yes would you change the Tiptronic oil and it's filter whist you are at it? By the way initial inspection shows no oil leaking between engine and trans and no strange noises. Thanks

Just lease it alone and if you ever get chance to have access to it due to another job then ping the outer dust seal off the bearing and check its ok. I had a new clutch a few months ago and checked it out (for a second time). 145k miles and the bearing is like new. Yes you have double row and most reliable. I'd do the millers sample so you have a start point and bench mark/reference for future oil sample comparisons. For a new owner the most important advice I can give you is don't take the engine above 3k rpm until your oil pressure has bottomed out at tickover (or at least under 2 bar), then once this is achieved (probably around 10-15 minutes running) drive it like your pants are on fire!!!!

Great advice thanks :thumbs:

Hi everyone, I am looking at a 2005 996 C4S MANUAL with 90k miles. The owner is having the EPS IMS fitted with a new clutch. This sounds good for my piece of mind but should I also be having the bore scope inspection? Can anyone help advise me please? If the bore score is clear, should I still expect that it might need repairing at some point which equals Hartech and a 10k bill? Thanks for any advice!

Quotes source post: 2692446

Read this thread from the start. If the car is at 90k miles then your best bet is just to check the IMS bearing at clutch change and remove the dust cover. Personally I would much prefer this than fit a replacement bearing. As for borescope, on a C4S it’s essential. But important to get it seen by a knowledgeable specialist who can differentiate between normal markings and actual problematic scoring.

The EPS IMS bearing is a bad idea....as is any other roller style bearing rather than ball bearing. Lee Jenkins (Hartech engine builder) is constantly posting on facebook how bad they are.

Quotes source post: 2692453

Many thanks. I have now read the thread which is very informative. An independent inspection seems to be a must. Being non technical I struggled around the IMS question but will reread again later. The larger bearing fitted to later cars seems to be the way forward if there are issues on the 996 c4s. I will look at Hartech website for costs. Thanks all.

Quotes source post: 2692455

Oh ok. Thanks for the info.

I had a great call with Grant at Hartech regarding the engine, bore, IMS etc. He was incredibly helpful and explained everything very clearly. Thanks for the advice everyone

Quotes source post: 2692752

Pleasure - glad you spoke to Grant. They’re great, very happy to chat even to people who don’t own cars (but are about to!)

Best lads in the business.

Deleted post.

Hi I haven't read the whole post, but if rebuilding the engine, then Hartech do the larger 997 bearing pressed onto the 996 IMS shaft. Thats what we went for. Berni

What's the consensus for a high mileage engine that has no apparent issues? I have read the Hartech posts and understand the logic of what is proposed, but I don't really know what to do in my situation: I have a 2004 996.2 at 95k miles. It's never had a replacement IMS as far as I can tell. It does not need a clutch replacement and has not had one. It doesn't exhibit any other issues that imply an engine rebuild is happening soon. Do I literally just monitor oil condition religiously and change frequently, and try to catch a degrading IMS before it happens, then go for the 997 solution with Hartech? Or is there any benefit to pre-emptively doing that solution because it's a 95k mile old IMS and in reality it's probably getting a bit long in the tooth so just do it for peace of mind? Sorry if this has already been answered - I read through everything and this is the one question I am still a bit uncertain about.

The answer - leave it alone. When it comes to doing a clutch change, inspect the bearing (where you'll find it perfectly OK) and ping the outer seal off it so the fresh engine oil lubricates it, then forget about it. If you ever go for a full engine rebuild, consider going to the larger 997 bearing, as this can only be done during the rebuild process.

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I like this response but what if you are in a similar situation but with a tiptronic? (2001 Porsche 911 3.6 996 Carrera 2 Cabriolet 2dr Petrol Tiptronic S).....also what's the going rate for upgrading the IMS on say a car thats done 70K and with a great service history....I'm reading £2K is about average?...