996 IMS Issue - How real is it?

Hi All, I've been looking at a few 996's of late, and in doing some research have come across the IMS issue. I've had a chat with the service manager at my local PC and he's told me he's only seen 2 in 8 years. I know it can happen, and I know it does happen, but I'm just wondering how prevalent this issue actually is. cheers

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From all accounts on the internet not really that common. Have a look through this recent thread http://porscheforum.com.au/topic/7958-996-good-value/

Agree not overly common. For the sake of a few thousand dollars to get it fixed, the first thing I'd be doing if I purchased a 996 Carrera would be to get the IMS fix done simply for piece of mind. The cost of getting a motor fixed after an IMS has shat itself is a lot more so to me a few thousand spent on preventing IMS issues would make me sleep a lot better.

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Might be worth contacting your local independant Porsche service centres.. They may have come across more than the official Porsche centres. I'm not sure how many people would still take a 996 to an OPC in general... So far, I have only come into contact with 1 person who has experienced failed IMS themselves.. they were selling a Boxster S and ended up with a bill of $25k....

Hi, I have had a 996 for about 9 years. My Porsche specialist guessed IMS failure was effecting about 5% of engines. He had seen a few but not many. I changed my IMS bearing about 4 years ago to the LN engineering ceramic. No issues. Cost was about $2000. If this has not been I would recommend pricing this into the purchase price and getting it done for peace of mind. Remember that if a car is still on original engine it will be a 15 to 20 years old and everything is getting on a bit so if a part was already a weak point it probably a lot weaker now. regards AndyS

I was in at Buik Motorworks just before Christmas.  I was asking the same question.  Mark said of all the major 996 engine disasters he's had to fix only 2 or 3 were IMS issues.  Cracked heads & split bores were more common.  I researched 996's quite a bit, before I decided not to buy one.  Not because of any reason other than I decided to buy a new car.

I think it's something like 1% of 3.4l and 5% of 3.6l or something like that. Factor in an IMS upgrade for peace of mind. It will make selling the car down the track easier also as it will be more desirable.

If I had to do it all over again, I'd be clear on my goals for the car and enter a purchase at the point where I thought would be comfortable with the total $ spent in say a 3 year period of ownership. One goal I may have considered is low cost high mileage car then go for the refresh scenario. eg. If you only ever wanted to spend $40k to own a porsche, then you could assume $25k for a new 3.8l engine and $15k for the purchase price - give or take In the end, things are mechanical, these cars are aging and ownership has been fun regardless. It's hard to put a price on passion and happiness!

Thanks for the responses thus far.

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I'm with you. I just got a 2004 C4S with 56000 km.  I'm going the permanent IMS fix.  $2500 well spent. The y say the trick is more regular oil changes and this ones got a solid history there but ... Porsches have had niggling issues as well as bigger ones in the past.  Think chain tensioner upgrade when you're looking at an aircooled car up to 1989.  Its much the same in terms of the thinking. Get it done or see it done and you feel better.

Don't you mean 1983?  ie Pre C3.2

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Erm, yep. should check for typo's... apologies

The m96 needs periodic maintenance items I've mentioned elsewhere on this forum. The IMS is one of them. Go the LN engineering IMS solution and it is out of the equation for life. Porsche made short sighted engineering designs in a few models in my view. Nothing drives like one though. ?

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Its booked in for the LN Engineering fix.  Best solution I could see out there. They're a great thing.

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It really is a no brainer if you want to sleep easy at night

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The M96 engine is a really nice unit but every time I gave it the big rev I winced ... I know that revving doesn't trigger the issue but you get my drift I've driven the 3.8 that came in with the 997 and I think the M96 engine is the sweeter, freer feeling engine.  Not much in it on a day to day basis other than the bragging rights with 200cc ...

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Exactly what i did .

I have heard it is most common in cars that were molly coddled and never driven properly(IMO). If the engine is revved out regulary it keeps oil in IMS but cars that never see the right side of 3000 RPM the IMS can be starved. No idea how true this is but would make me steer clear of any cars owned by elderly librarians<joke Im sure some would drive the cars properly I'd also cough up for the fix, as no one wants a 25K bill

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honestly officer, i was only driving flat out 'cause I needed to make sure my IMS was not starved of oil

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Not sure that works, particularly when you drive a GT3 Blue

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ok, i'm being optimistic and hoping the officer doesn't know my gt3 has a mezger engine

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Just recently got the news ... ordered the major service on my newly acquired 04 GT3 CS and got the fateful call:- "Erm, mate - we cut the filter and well, do you have time to come down and take a look?"  Seems there was a little metal particulate in the filter.  ARGH!! The thing only has 38000km on it so not sure of cause yet but the engines out already so soon we'll know.  I'm tipping bearings. A new thread on the rebuild?

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just...noting...that...down...for...future...reference And here's everyone worrying about the IMS in M96's....

@Skidmarks that really sucks mate. Didn't think they had that issue. Let us know what the cause was once it's been pinpointed

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oh crap! Let us know how it goes.

Left field I know but. I had a mate had a cracked head issue on his 4x4. Short story he claimed on insurance, successfully. Worth a shot...

Thanks guys. Sh#t happens. I'd been driving the car as per normal (caning it ...) and no issues, noises, odd pressures etc.  I think we caught it early. Could have been a big issue if I'd not been conscious of the service being a little overdue. So it'll get the full freshen up now. At least I'll have the comfort of really knowing the state of the motor once its been rebuilt. The previous owner won't have given it a hard time but then again, who knows.  Could just be one of those things. I have a set of rebuilt 04 Cup Car heads from back in the day.  Might think about using them!  The GT3RS was used to homolgate those heads so it'd be true to type .... Or maybe I'll just leave well enough alone otherwise with my form I'll end up with a bl##dy RSR. I've also used the opportunity to tidy up some paint - gravel rash etc.

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WTH? Who's he with? He must know the assessor "very well"!

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Indeed.  I'll have a look.

Don't know. I only worked with him for four months and the head fix was concluded after I left. The 4x4 forum's have a lot of contaminated fuel stories, meaning pump rebuild claims paid. Water immersion too. Costs nothing to ask.

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That was really lucky! Glad to hear it's all being sorted. There's nothing wrong with an RSR either! (unless your wallet or other half demands otherwise)

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Sorry to hear! Who's working on the engine for you if you don't mind me asking? As for the IMS as the American's say treat it as a wear item and replace it when you get a clutch done (provided the car is a manual). There are also four "models" of LN bearing FWIW: IMS solution - "plain" oil fed bearing (never needs to be replaced), LN classic - ceramic single row bearing, LN dual pro - double row bearing that fits in place of an original single row bearing, double row ceramic bearing to replace dual row (early 996s). With the exception of the solution the pro and double row (not the classic) have an expected lifespan of 75k miles (~120,700 kms) or 6 years as per the LN website.

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The engine is getting done by Ray Dick who has been building my engines for the last 15 years.  He cut his teeth on the air cooled stuff and his favourite setup is an early motor that runs big comp, dual plugs, Himalayan spec cams and turns to a gazillion revs whilst running slide injection.  A true Porsche nutter.  I'm contracting him in through Shaun Cairns new raceshop,  Werks Garage, who takes care of the race cars and my fast road stuff. Ray's a complete wiz on the GT3 and Cup Car motors.  A few year back we were building an engine for my Australian GT series Series 1 GT3 and trialling some 997 heads and cams when he rings me up and tells me it's going to be another week or so as he was dialling in the cams and setting the cam timing bu wasn't happy with the factory tool so was making his own to get it absolutely right.  No sh#t.  A Porsche factor mechanic looked at the new tool and called it a thing of beauty and asked if one could be made for him to use! As for the IMS, the C4S is in now to get the classic fitted.  Toby at Cairns Service is doing that for me as Shaun is flat chat prepping cars for the coming year of club racing, circuit stuff and rallying as wel as building a hot rod for customer and building a new IROC car.

Update. The IMS is going into the C4S today.  No issues found with the one there but found some other stuff ... Cracks in all 6 coil packs.  Ouch. Doughnut to front needs replacing.  Ouch. Needs new clutch and dual mass flywheel.  Ouch, Ouch.  Toyed with the idea of getting something more "sporty" but put it out of my mind.  Its a road car ... Looking forward to getting it back and really showing it who's boss!  Getting it back by early next week GT3 motor out and being torn down as I write.  I'm hoping its all pretty straight forward and whatever it was I caught early but my inner pessimist has me counting the days before I get the "mate, got some time to come down and look at this?" Oh, and whilst I had the car immobile, I sent it to get some paint touch ups and fixing of gravel rash. Anyone out there familiar with the term "scope creep"?  The guy who owns the shop doing the work is a great mate so decided that I wouldn't be happy with a bit of splash and run and "suggested" I look at something a little more "comprehensive" to do the car justice. Apparently, "let me think about it" in fact meant "sure, take out the glass, rip off the doors and guards, take it all back, deal with all small dents and paint imperfections (aka the whole f**&%^$ body) and get the sucker ready for the Amelia Island concourse". Lucky I trust him!  He did add that what he really wanted to do was trial a new Glasurit concoction and that the paint and extra prep was on him so long as I could show the car to people. Oh, OK then ... Never a dull moment.

Glad to hear it's repairable and not terminal. I've enquired about touch ups on mine and it's the same story, whole car for a few chips around the bonnet and front bar

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What was the cost of the IMS fix and which one did you get? I think i'll do my C4S too.

GT3, GT2 and turbo cars don't have the IMS bearing issue. They have a plain internal bearing which is what the "IMS solution" developed by flat 6 and manufactured by LN engineering is based on.

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the IMS bearing is meant to be a sealed unit, the seal deteriorating and engine oil getting into the bearing is one type of failure (among others). So getting oil in there is bad. There's an LN Engineering kit that turns the bearing into an oil fed unit instead of sealed though, as well as replacing the bearing altogether. There used to be a thing called 'IMS Defender' but that was a light/buzzer that came on to warn you there was metal parts in your oil (similar technology to what they use in aircraft) - basically like "hey the clock is ticking before your engine implodes" I think there's a lot of stories about driving hard being better than not (as well as the inverse) but I think it's really luck of the draw if it happens to each car. But it is blown out of proportion on the Internet, much alike pulled head studs in a 2.7 has been for the past 20 years (although that probably affects more cars)

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I went for the IMS Solution that dan_189 refers to.  It's about $2500 installed so not cheap but the peace of mind as well as being able to say it's been done if you ever sell is worth it I think. but we're happy and that's all that matters! ? and chain tensioner failures pre 3.2 ...

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IAM_911 ( Ammar) from this forum did a fairly thorough investigation himself regarding the IMS, and installed his own solution, it's a very detailed thread and worth checking out The GT3/GT2 and Turbo engines don't have an Intermediate Shaft (IMS), so no requirement for a bearing (the cam chains are on the same side as the earlier engines and gear driven, whereas the M96 have them on the other end, and the IMS transfers 'drive' to them) and it's fed by engine oil, so i guess they could say it's 'developed' from, it's a pretty long bow to draw on their behalf.

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$2,500 is not expensive either. Is it locally available? and can pretty much any independent Porsche workshop just order the part locally and do the job?

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yes, it's available to local suppliers. The guys that did mine actually went over to the US to visit LN and do a little training but I'm sure that most reputable independents could do the job. As I understand it there are some really good guys operating out of Perth so you should be right.

I bought this one - another option perhaps http://www.vertexauto.com/ShowItem/294103 IMS Intermediate Shaft Bearing Upgrade Eternal Fix.aspx

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The Americans fight about ball bearing vs. roller bearing. I went the L&N because of their reputation. If I was going to do it again i'd consider "the solution" was only that the bill for a new clutch and IMS was already starting to top 5K and that was in my 2nd month of ownership! The additional cost was a sprung clutch disk I needed for my light weight flywheel. I did get the L&N Dual row pro though next clutch ill consider the solution!

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100%, I was exhausted with reading and procrastinating. I purchased my 996 off a friend about 5 months ago. He replaced the OEM bearing (found to be in perfect nick) with a ceramic (old style LN - I am quite sure) about 3 years ago.  (80,000kms is the used by of that ceramic bearing). I bought the vertex bearing after owning the car for 3 weeks and its been staring at me from my desk on a daily basis. My indie will install the vertex next week. Will be interesting to see, but I wont be surprised if the ceramic is in perfect condition. Love the internet and the anxiety.

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My head spins every time they start up the debate again! Especially when someones engine has blown up and they blame the bearing. I just get in my car and drive it, usually clears my head of all that... Oh and the fact I have the 2nd get LN bearing, that helps too

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strictly speaking the mezger has one IMS and the m96 has two, one at either end.  911/930 engines have a IMS as well.

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Amen,

I have 996 and I've asked around as well very rare occurrence and the only one my mechanic has ever seen was on a track car that was redlined every gear i emailed Porsche when I was looking at mine a few years ago,  and they said not to worry unless u plan on racing if it was going to let go, it would have done by now

When I enquired a few years ago I got told the same thing. I replaced it anyway not worth the risk the fix is a $1500 insurance policy

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I recently purchased a 98 model 996 and did a fair bit of research prior to doing so. The IMS issue was something that although relatively un-common especially on the 3.4 with double row bearing, was something that made me a little nervous to the point that i decided to do the LN Engineering IMS upgrade on whatever car I bought purely for the peace of mind. There is a lot of information on the inter web and it is a reasonably easy task if you have basic mechanical ability and reasonable tool kit. I bought the bearing kit from Autohaus Hamilton for $1200 and the IMS tool kit from a seller on Ebay for $180. I also replaced the water pump and thermostat at the same time as this is another known failure point. The IMS took me a whole day to do on my own, luckily I had access to a hoist as it is a job I wouldn't attempt to do on the ground. The water pump and thermostat took a couple of hours, the most frustrating  part of that was refilling the coolant and bleeding out all the air. I chose to completely flush the cooling system and replace the coolant while I was at it. I used AC Delco dexcool as it is readily availably and meets all the porsche coolant requirements and was recommended by a radiator reconditioner  I know, who said from experience it is the best coolant he has come across for aluminium engines. Use the genuine water pump with the plastic impeller, don't use the one with the steel impeller. The genuine water pump is only about $400. Back to the IMS, although my bearing hadn't yet failed and there were no metal fragments  in the oil sample i took upon purchasing the car. When I removed the old bearing there was a substantial amount of dark smelly engine oil trapped in the intermediate shaft that had made its way through the original bearings seal's and was getting cooked everytime the engine was running without being cooled or filtered. The fact that the oil had made it to that point ( the other side of the IMS bearing) means it had already diluted and washed out the grease lubricant that this bearing rely's on and it was only a matter of time before the grungy oil that was building up in the intermediate shaft worked its way back through the bearing and caused the bearing to deteriorate and eventually fail. My car had 130,000k's on it when purchased and I'm glad I didn't ignore the IMS issue, it is obvious it would have bitten me eventually. Anyone with a 996 or boxster or anybody thinking of buying one should treat the IMS bearing like you would a timing belt on other cars for peace of mind alone, they are usually replaced around the 120,000 km mark. There are other things that can go wrong with 996 engines but i have the peace of mind of knowing that I have reduced the risk considerably by replacing the IMS and water pump.

LS, Great "hands on" work and write up. I agree with your pre-emptive replacement approach.  However I'm not so sure that the bearing failure is primarily related to lubrication, whether that be grease, oil or combination thereof. For the purposes of research, could I have your old bearing please?  Happy to pay postage etc. Regards Peter

Hey diggin, if you have no further use for the tool I would like to buy it. Pm me if you're interested.

I just got the C4S back and they said that the IMS was fine. Still very happy to have had it done. Peace of mind and a great selling point. The new clutch, pressure plate and flywheel -  a bit of "while you're in there ..." as well as a full service added significantly to the bill but it's all as good as new and ready to enjoy.

Hey Skidmarks, Wasn't me. I think LS1RX7 is the person you're after. Anyways, ended up getting a MY09 987 Boxter S.

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the one at gulsons for 69,990? Can i ask how much you paid?

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Hi firstone, It was me that has the tool kit, when I purchased it I had intended to sell it on after completing the job, but have reconsidered now as i may buy another 996 in the future and it will be a handy kit to keep in the workshop. This is the one I bought on eBay it has gone up in price, I only paid $189.00 au in December 15, i hope this helps. Porsche IMS tool kit for 996 986 Boxster Carrera

☺ I realized my mistake but never got back to correct. Thanks for the tip. I want to do it myself as well.

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Hi Peter, I'll check if I still have it, I have established a habit recently of throwing out worn or replaced parts, as I found I was hoarding too much stuff that was never going to be used again. If I can find it I'll get back to you for address details.

Is that tool a replica of the LN tool? If it isn't it can only install the classic LN bearing rather than the pro one. If you're doing the solution I dont think it matters.

I used it to do the double row in my 1998 3.4L

Ah right, so the 3.6 has a single bearing so do late 3.4s. There are 2 LN upgrades available: Classic which is a ceramic single row or the pro which is a dual row in place of the single which requires a specific LN tool to install.

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EPS bearing in. Old bearing out. The IMS old bearing is in perfect nick. As expected.

Hi Macca, The best case scenario is removing the old bearing to replace it as a preventative maintenance item and finding the old bearing in perfect condition. A less than ideal situation is to find that the bearing has already deteriorated and started shedding metal particles that have been traveling around the engine doing other damage, or worst case the bearing collapses and causes a catastrophic engine failure costing potentially 10's of thousands of dollars. In comparison the cost of replacing the bearing as a maintenance item every 120,000 kms or as LN suggests every 75,000 miles is relatively small for longevity and peace of mind. Just like a timing belt on other makes of vehicle that have to be replaced at around 100,000 klm's. As for the EPS cylindrical roller bearing, I had a couple of people advise me to stick with the LN option as the EPS one hasn't been around long enough to prove itself and one Porsche specialist said he had already heard of some issues with it. I do believe that some LN bearings have had failures as well, nothings perfect but either option has got to be better than leaving the old bearing that has demonstrated the potential for failure whether it be from lubrication issues or lack of load allowing balls to skip as has also been  suggested. Either way there is a potential issue, some cars are doing 200,000-300,000 k's on the original bearing and some less than 60,000. Regardless of which option somebody chooses, I would recommend doing an oil sample analysis at every oil change to establish a baseline and monitor potential wear so if there is a problem developing you can catch it before it does to much damage. You may also find another component at risk before it fails. We do regular oil samples on our earthmoving equipment for this reason. I know other components can fail other than IMS bearing,  but I now have more peace of mind after replacing the IMS and water pump and can enjoy owning my Porsche rather than stress about it. The 996 has gotten a bad rap from the purists as well as it's reputation for potential engine failures, but if you can live with the boxer style fried egg headlights and treat the potential known engine issues as maintenance items, it is a much better car than it's predecessor's at a fraction of the cost of them or the 997 which still has the same potential issues. The 996 is a real Porsche and really is great bang for buck as long as you do what you can to make sure they don't go bang.

And what about cylinder scoring or whatever..  I know its not IMS - but is there much weight to this issue as well..?  Separate thread perhaps but do you have any thoughts on that..? And what's this about cold starts.. Is the 996 really plagued..?  They got described to me yesterday as a 'ticking time bomb' and not a matter of IF but more a matter of WHEN.

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it really happens. A for "IF but WHEN" no mechanical part will last forever, regardless of which kind of car. Google "bathtub curve".

Hi WOKA, I believe there are several other potential issues with the 996 as I did a fair bit of research prior to buying one, but that goes for any car really especially when you consider that early 996's like mine are 17 years old now. Cylinder cracking is another issue that has occurred in some cars  but again this issue is not exclusive to Porsche 996's, cylinder cracking is a risk to any internal combustion engine. A bit like IMS bearing issues you don't hear about the many thousands of ones that don't fail, only the ones that do. I think the reason there is so much about the issues of the 996 on the internet is that someone that owns or wants to own a Porsche usually has a passion for the brand and will try to find out as much as they can, and those that already own a Porsche like to share their experience's good or bad because of that same passion. I also think one of the reasons the 996 gets a lot of attention on the internet when it comes to failures is that the cost of major engine failure can be lots of money compared to falcon or commodore but owning a car like a Porsche 911 is a lot different to a falcon, commodore or other mass produced car. Porsche ownership is still new to me but from carrying out the IMS bearing replacement and water pump replacement as preventative measures I got to see first hand how well these cars are engineered and put together. As for ticking time bomb, I think that applies to any internal combustion engine it's just that the Porsche engine is going to be more expensive to repair than a ford or holden but same goes for any european car. I weighed up the the fact that you can buy a good 996 for under $40,000 at the moment, (I paid $30,000 for my 1998 manual coupe with 130,000 km's and a complete service history.) against what else you can buy for the same money, remembering that a 996 is a 911 and a real Porsche, all 911's are considered to be supercars of their era. I negotiated my purchase on the basis that i always intended to upgrade the IMS bearing and replace the water pump as they are the two main items that can cause a major failure and are able to be carried out with the engine still in the car. I am also fortunate that I am able to carry out the work myself, at the end of the day it wasn't that hard, when you look at it a Porsche is the same as any other car in so much as it is just nuts and bolt's, I'm not a mechanic I just have a passion for cars and in particular Porsche 911's. If you have some mechanical knowledge and ability there is plenty of information on how to do work on your 911 and that can make ownership both economical and enjoyable. If you have to put it into a workshop for everything in can get expensive. I maintain that in my opinion if you buy a 996 with a service history and deal with the known issues as maintenance items then the 996 is great value for money when you consider you are buying a true supercar.

Anyone actually just replace the bearing with an OEM Porsche one if its being treated as a service item? - Or are the designs fundamentally different..? On a side note the 996 I just bought had the clutch done 15k km ago and the guy was advised to leave the IMS bearing alone by an independent as it as it had the "newer" one?? I'm now deliberating whether to get it updated. I did speak to his mechanic and he said he had inspected it when the clutch was being done and there was no visible indication that there was an issue and there was no play?? Jim.

There were revisions through the years. I wouldn't trust the original though. That mechanic wouldn't have been able to inspect it because removing it isn't overly simple.  For piece of mind get the LN pro.

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It's the next thing I'm going to do.. It's weird as the previous owner actually asked to have it done and was told don't. Jim.

When I was researching the 996 I called the dealership who told me "if it hasn't gone by now it won't". He was probably right but it's too big a risk to not have it dealt with. $1500 for piece of mind.

Hi Jim45, You can't inspect the bearings condition without removing it, once you do remove it, it can't be re-used as the removal process relies on pulling from the centre stud. This puts pressure on the balls against the shell which in turn can create  small flat spots on the balls which if re-used can cause the balls to skip intermittently and the flat spots get worse and start damaging the bearing surfaces which starts a downward spiral of deterioration which can accelerate rapidly. Porsche doesn't sell the OEM bearing separately, you have to buy the whole  intermediate shaft assembly. There is some differing opinion on the cause of IMS failure, from lubrication issues due to the seals failing and allowing oil to pass through the bearing into the intermediate shaft washing out the original grease to lightly loaded contact allowing the balls to skip which then starts to multiply the damage. The other thing to consider is that there are many cars out there approaching 200,000-300,000 km that are still on there original bearing. The low km cars are the ones that seem to be most at risk, probably due to seals hardening through lack of use. early 1998-2000 model cars with the dual row bearing were at least risk with a 2% failure rate 2000 model onwards with single row bearings had a 5% failure rate. My car had 130,000km when I bought it last year  and i didn't want to take the risk leaving the original bearing in there. When I removed the bearing it was intact and showed no signs of wear or play however there was a lot of really grungy bad smelling oil that came out of the intermediate shaft itself from behind the bearing. This was engine oil that had made it past the original bearing seals and into the hollow shaft, the oil then gets cooked every time you run the engine and can't get back out to be filtered or cooled or replaced at scheduled oil changes if you maintain the correct oil level in  the sump. This oil breaks down and becomes acidic and if it works its way back into the bearing  usually due to lower than optimal oil level which may only be 1 litre of oil lower than optimal, it can start to damage  the bearing and cause the downward spiral that will continue regardless of oil supply. So whilst my bearing was still ok the bearings seals had been compromised meaning it was probably only a mater of time before failure cycle would have started had I not done anything about it. My advice if you don't want to change it now would be to have an oil sample taken and analysed and then have another one at 5000km later to see if there is any over the top level of wear metals present, or if there is a small amount present  and in most normal cases there will be, compare the two samples and see if there is any dramatic increase to determine if there is a potential problem developing. Be diligent with checking your oil level and keep it at optimal level using the dipstick rather than the gauge but don't over fill it. Having the bearing replaced should give you peace of mind. In my opinion replace the bearing with the LN engineering one and sleep better at night and enjoy your Porsche instead stressing about it.

My 2 cents I've picked up an immaculate C4S that has a faultless ppi and is in showroom Cond. Im getting the Ln solution done before I drive her home you know it makes sense. If it's a 30 or 40 or whatever $$ car it's damn cheap insurance. Keep out of the kitchen if you can't stand the heat cheers lads

Agree totally Hughesy, you buy a Porsche to enjoy it, you don't want to be stressing about it.

If it's a known issue that can be catastrophic, and an upgrade resolves the issue, I can't imagine a valid argument for not doing it upfront for total peace of mind... why would it even be a discussion point worth 3 pages of forum?

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Couldn't agree more, thank you for the comprehensive and informative post. The LN bearings (without oil feed system) I believe last approx 80k before advised to replace (I guess same as the recommended clutch service), What was the issue with the EPS bearing? (It either fails [boom] or keeps turning - so to speak)  Hopefully the only major issue with the EPS is lack of history and feedback. Hopefully my experience with the EPS (and oil feed) is as paid for. EPS oil feed - https://www.youtube.com/watch?v=DfXjx0tvaMA

Got "the call" today On the GT3 motor. Not pleasant. Apparently before I got it it had had a BIG over rev which caused the chain guide on one side to come away and deposit various bits of itself in and ar9und the sump. Caused an oil starve to the main bearings on one end of the crank but seems crank is OK. Lay shaft may also be bent. Leak down on one side was great, the other not so much ... Some strange bearing wear as well and I'm going to have a look just out of interest Usually I'd do the whole PPI but bought it from a known source. That said, knowing him as I do, there's no way he would have known what had happened. It had just been out at a club day at the Island and I think that's where it happened. I picked it up from him the week after and it wasn't running badly as if the valves have only had a light kiss, normal running is seemingly unaffected. So, crack testing the crank to be sure, giving it a big clean out, new bearings all round, new rings, check the heads and if need be replace valves and check the seats, new rod bolts and, well ... Write a cheque. I bought the car well and even with a bug cheque I'm still ahead and at will least now know how the engine is good for a long time to come. BTW, the paint job is the best I've seen.  They also used this very trick clear that if you get swirls in it after washing for a while, you leave it in the sun for a couple of hours and the swirls disappear. Voodoo shite but they sweat it works. Who cares, it looks fantastic.

Update. Crank tested and is fine. Got the parts list for the rebuild. Porsches parts target budget for the month of April just got a BIG lift.

I've been driving the C4S a bit lately and since the IMS fix, I swear that the oil pressure has improved.  At idle it sits at around 3.5 on the gauge but on the move its locked on the 5. I could be wrong but I look at my guages a bit and it struck me as really good.  Or maybe it's just that on the older ones I have the pressure is, shall we say, a little more "relaxed". Anyone seen anything similar?

Unlikely the IMS replacement will increase oil pressure, but if you changed the oil with different brand and weight it can achieve this. My oil pressure has increased since I replaced my IMS but I also went from Fuchs 0W-40 to Penrite 5W 40. Car doesn't use any wear near as much oil as it was prior to this change either.

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When you say using oil, in what way was it loosing it? More smoke on startup? How much more would you use per x kms between services?

I think it was just burning the oil because the oil was thinning out too much when at operating temp. It wasn't obvious where the oil was going as it doesn't have any leaks and doesn't blow smoke on start up or when operating but it definitely used oil. I purchased the car in Sydney and drove it back to Townsville which is a bit over 2000 km, it used 1.5L on the trip with the Fuch's 0W-40 oil that the previous owner was using. Since I replaced the IMS and gave it a service replacing the oil with Penrite full synthetic 5W-40 it has done about 4000km and has only used about 500ml. It is a 17 year old car so I would expect some oil usage, and when you look at all the forums most 996's do appear to experience oil usage, some more than others. From my experience owning earthmoving equipment, trucks and racing cars, oil usage is not only caused by engine wear but can also be related to oil brand and type. I used Gulf Western Top Dog XDO diesel engine oil in my excavators for a while and on one particular machine it was noticeably blowing a small amount of smoke consistently and used about 7 litres between services. I switched to a Castrol oil and it stopped blowing smoke and only used about 2 litres between service. I think the old saying " Oil's ain't oil's" rings pretty true.

With oil consumption just be wary about before and after comparisons where the car has been sitting a long time and only done short trips or brief start ups as the oil can accumulate some fuel dilution and moisture giving a false reading that only becomes apparent after its next long trip. The other issue that complicates oil usage comparisons is usage where sustained high rpm will use more than just poodling 'round town.

The service manual also calls out maximum oil consumption at 1L per 1,000kms (for a TT) didn't look for a C2 but I can if anyone wants it

Gday dan What's the expected consumption for a C4S Thanks Hughesy

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Hey Hughesy, Same as the TT Cheers

Back on the IMS thing.  I had dinner with a good friend of mine last night who sold his early model 997 Carrera about 4 months ago as he lost his license for speeding... Lovely car everything you'd want it to be.  Well maintained and serviced and looked after.  An auto so no money shifting going on etc.  No monkey business or back stories etc. Last week he gets a phone call form the guy who bought it and was told the IMS bearing had shat its self and gone right through the engine.  Porsche told him it was a $50k fix. Halve that and you're still screwed.  Car on finance and was only worth $75k. Nobody's fault... This is as first hand as it gets so it 100% could happen and personally I'd not leave it to chance. Just sayin'. p.s. I asked my mate if he would rather have lost his license for 6 months or have it happen to him. He picked the former so in a twist of fate, a silver lining appeared...

Geezuz fn cripes! Ok who's got a 997.1 S man coupe to unload - $35k cash waiting, and in being generous!

This is as real as it get's, someone from Newcastle on the forum has just dodged a very expensive rebuild. Heard an unusual noise and put the car in to the mechanics, pulled off the gearbox and checked it out and sure enough the IMS is on the way out, series one 996. I like these cars but this really puts me off them.

Any idea how many ks it'd done Porky?

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Most of the series 1 996s have the original dual row bearing and it had a lower failure rate than the series 2. Mine is a series 2 and its the first thing I got addressed with the dual row pro by LN when I bought it. Not a great story that has just been mentioned

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I'll check but it was low.

I seem to remember some info on here a few times about, it seems to be the low ks ones that have been nursed are a common denominator amongst the implosions..

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went kaboom at 44k klms.

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I have read this too, best to just swap it out as insurance.

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that's the way I looked at it. Factor it into the purchase price. I went with the IMS solution on my 76,000km 996.1. Bearing was fine when they pulled it out but that is not a good indicator of what will happen in the future

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That is exactly what I did, I planned to change the IMS bearing on whatever car i bought. If you treat it like a maintenance item just like a timing belt on other cars you would be pretty safe. I changed IMS and water pump when I bought mine along with a full service all fluids including coolant for peace of mind. I am fortunate enough to be able to do the work myself it cost me under $2000 for all the parts and special tools and only took me a day.

Awesome that you could do the work yourself! I had to get a "specialist" to do it the experience was horrible but that's another story. I'm a fairly savvy DIYer but that was something slightly beyond my ability, especially with the importance of that bearing... When it's up for replacement, if I still have the car ill be going with "the solution". I also have the LN SOFA installed for extra protection

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Without doubt.  It's one thing reading about this stuff on US forums but when there are real and local experiences, who could possibly take the risk given the consequences?  I for one couldn't ever drive it without there being a lingering doubt about it and it would ruin ownership for me.  Negotiate it into the sale and if the seller isn't open to the truth about it then you have to factor that into your decision.  You're buying a $50k car that has had all of the depreciation come out of it and represents amazing value.  Pony up the cash and fix the damn thing already.

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That's it exactly

I spent two and a haif years looking at 996's and 90% of the owners had no idea of the issues with these cars but does make a great bargaining tool when its time to negotiate a deal and like most informed buyers of a 996 it was sraight off to have the IMS sorted.

Just as data point - recently did the ims solution car had 135k kms. ims looks pretty good actually (actually looks new to me), seals intact etc.  ( i haven't removed them) no play except for when i put a kind of yaw motion on it but it's super slight. it's also the single row one. Spoke to the mechanic (porsche specialist) and they've only done 3 (i think) over the years. A lot of people ask about them, but no one ends up doing it and mentioned they've only seen one failure from a boxster. So maybe it's more a US thing, with their harsher climates?

Had the IMSB replaced recently at 185k Kms as engine had to be dropped anyway to replace brake lines, get manifold studs and a new AOS.  Original IMSB seemed as good as new.  Replaced it with FVD Brombacher steel bearing.  1999 3.4 C2. Original IMSB for sale if you're feeling brave ?

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When I replaced mine the old bearing appeared fine and seals looked to be intact, however when I removed the bearing a substantial amount of black evil smelling engine oil came out of the intermediate shaft. The bearing felt ok but free spun more freely than you would expect a sealed for life bearing to spin, possibly indicating the original grease has been washed out by the oil that made it into the IMS. While it was still intact the life of the bearing ongoing would be limited now that it was lubricated by the oil that had made it past the seal and would have been deteriorating in the bearing without being replenished. Fortunately for me the bearing hadn't started to fail but I guess it would only be a matter of time. As for possibly only being a US problem, I doubt it. I believe poor design idea that shows itself occasionally regardless of climate. I'll stand by upgrading as a maintenance item for peace of mind. When I replaced mine the old bearing appeared fine and seals looked to be intact, however when I removed the bearing a substantial amount of black evil smelling engine oil came out of the intermediate shaft. The bearing felt ok but free spun more freely than you would expect a sealed for life bearing to spin, possibly indicating the original grease has been washed out by the oil that made it into the IMS. While it was still intact the life of the bearing ongoing would be limited now that it was lubricated I'm pretty sure you're being humorous there. Even inserting a new bearing and then removing it without using it will render it defective as the pulling force on the bearing during removal is likely to cause small flat spots on the balls that will quickly increase during use and likely cause a devastating failure. When you install a bearing the forces are applied to the outer shell but when removing you are pulling from the inner collar.

Yes you'd be insane to reinstall the used one! Here it is.  NSK made in Japan. FYI this is the Brombacher bearing. https://www.fvd.net/de-en/FVD10590104/intermediate-shaft-ims-repair-kit-m96dual-row.html

Here's my badge of honor. Interestingly it's an NSK part made in England!. doesn't spin super freely so i think there's still grease in there.

Whats the lifetime like on the FVD bearing?

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Have just been having useful email discussions with FVD, who confirm that the only options they supply for single row IMSB is the ceramic bearing.  This is NOT the LN Engineering option, but their own supply. They say in advertisement that 100k kms is the minimum expected life for both options.

There is a guy on the petrol head forums called POP POP BANG BANG. I've spoken to him about the IMS bearing issue and to be honest it didnt phase him as his done 550,000 on the original bearing. Dual Row, the guy is a F1 engineer and drives his Porsche around the euro roads to deliver last minute parts and so forth. He said that most of if not all the faulty ones are from cars that sit all winter and barely get driven. I'd take and F1 engineers word over a lot of work shops. I understand people freak out about the IMS which is justifiable as its a costly repair/replacement. However, if you're buying a 996 to have it sit in the garage then its more then likely going to seize something and that something is the IMS bearing.

I reckon its related to engine speed.  At lowish revs the torsional vibration in the IMS causes the balls to skid rather than roll and this causes the bearing to fail.  With the revs up, the vibration reduces and the bearings last.

I replaced my bearing myself and discovered that the bearings seals had failed and allowed oil to accumulate in the intermediate shaft. When removing the old bearing there was a substantial amount of black evil smelling engine oil that came out of the shaft. The likely scenario is the previous owner kept topping up the oil as the level dropped and due to failed seals in the IMS bearing the oil was gradually filling the shaft and every time you top up the oil you trap the oil that has made it into the shaft. This trapped oil then gets cooked again and again without the being filtered and eventually turns into an acidic, grungy substance. If allowed back into the bearing by a low oil level then it is likely to start to cause damage to the bearing due to poor lubrication and once a bearing suffers damage it will accelerate the deterioration with use ending up in a catastrophic failure. It makes sense that cars that are driven infrequently suffer the most failures due to half the seal being immersed in oil and the other half allowed to dry while inactive for long periods, as the correct oil level is about halfway up the bearing. An open bearing with no seals such as the LN ceramic allows oil to pass back and forth through the bearing therefore the oil can't get trapped in the shaft and turn into the ugly stuff that came out of my IMS. I believe I was fortunate enough to escape disaster that would probably have been inevitable based on what I found.

996s are a minimum of 13 years old. Likely the car you own has been owned by many before you. How could you possibly know how it's been driven and use this as a basis of a decision. Probably. Probably it won't happen, but if it does it's going to hurt your wallet badly. You insure things that are low probability but with high financial consequences (ie car insurance) so why apply a different logic to this situation? My first hand story is above and it was ugly for the owner. Would totally ruin the ownership experience. I would personally not consider owning one without it being done and consider it a necessary piece of preventative maintenance. It's also not THAT expensive either IMHO. The bill would be small compared to the $$ dropped maintaining those old aircooled cars. In the end it comes down to your temperament and how you see the world. My 2c. Wishing everyone the best of luck

Agreed, that is why I replaced the bearing in mine as a mater of urgency once purchased. Treat it the same way you would with a timing belt on other vehicles. Cheap peace of mind and makes ownership so much more enjoyable without that "what if" always niggling in the back of your mind.

Not the best thought out design but It's not bore scoring or broken head studs. It's just a bearing to be replaced.

good article on pelican - http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/13-ENGINE-Common_Engine_Carrera_Problems/13-ENGINE-Common_Engine_Carrera_Problems.htm

Interesting little video which I found the other week. I'm sure it's already been covered on the renn forums before, not sure if on here though. It makes reference to what @LS1RX7 was talking about with rancid oil inside of the intermediate shaft.

The root cause of the failure isn't related to lubrication. If it was you would see similar rates of failure over the three different types of sealed bearings Porsche used over the life of this engine.  Further, you would see similar rates of failure between the Tiptronic and the manual transmission cars. Also if the lack of lubrication flow/bad oil theory was the true, the commonly used open ceramic replacement bearings wouldn't have to be replaced in the remaining life of the engine either. Irrespective of what you believe the true failure mode to be - TV or Voodoo, I'm with Porks, I'd change the bearing to preferably the plain bearing "IMS Solution" type and put this issue to be bed permanently.

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The IMS solution is a direct oil feed onto the bearing... so I'm not sure why you'd prefer the solution over just changing bearings after you just said the problem is not lubrication related. That's one hell of a confusing argument you're making there

They are all lubricated. To my mind the plain bearing is most likely a permanent solution therefore giving you and the next owner more confidence. Just like saying I replaced my broken head studs (all 24) in the A/C with the best known solution.

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There are two options from LN (among other vendors) but LN is the premium. Their IMS 'solution' removes the original bearing and replaces it with a 'plain' bearing - which needs to be oil fed to be lubricated. This is a solution for the lifetime of the engine as there are very few wearing parts. This plain bearing design is used to support the IMS (shaft) in the GT3 and TT engines. However the oil feed needs to come from somewhere so there is an adapter at the oil filter. Your engine bellhousing also needs a hole cut out of it to allow for the supply line to the bearing. The retrofit on the other hand replaces the original bearing to one of a similar design but with more robust components and in the case of single row bearings changes it to a dual row with ceramic coated ball bearings. This bearing had a finite life but is a direct replacement and no oil feed is required it is splash lubricated by engine oil. So in conclusion, 'solution' is lifetime and more expensive retrofit is cheaper but has a finite lifespan. Depends on your budget and plans for the car for which one you should choose.

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Mike, The point I'm making is that a plain journal bearing copes with the torsional vibration that a bearing with rolling elements sometimes can't endure. Imagine the wildly varying load at low engine speed that driving the valve train of 3 cylinders places on the shaft that is also compounded by its drive from the crankshaft being highly variable in its rotational accelerations as well. Forget that plain bearings are often pressure fed, forget lubrication, it's the suitability of bearing type that is my point. These issues are well known elsewhere in automotive engineering with the Ford DFV valve train reliability challenge probably the most famous example of destructive TV in practice.

For those with more time on your hands than me..... these guys are well known in the UK of knowing their stuff https://www.hartech.org/ https://www.hartech.org/images/downloads/Hartech Engine Guide (interim).pdf

I dont have a W/C car but read this forum if I see something interesting. I note that the original IMS bearing is a Japanese NSK, which does seem odd. But wasnt it the Japanese (Toyota?) that 'helped' design the heads for the Boxster / 996 so they could be manufactured very much cheaper than a traditional flat 6 engine? Perhaps this is how the NSK IMS bearing arrived and I wouldn't be surprised if that bearing has a has a close relative in 1990s Toyota somewhere.

I've read a few similar things around Porsche learning to share more parts across models and cost savings around the transition from A/C to W/C as well. I think the last article I read or video (can't remember) was that it was very expensive to manufacture the 993 compared to the 996.

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GT3 and Turbo engines don't have  IMS bearing or an IMS.

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The purpose of the intermediate shaft is to drive the camshafts indirectly off the crankshaft. By using an intermediate shaft, the speed of the chains are reduced, which is better for chain life. This basic design was used throughout the entire lifespan of the aircooled six-cylinder Mezger engine used through 1998. The inclusion of an intermediate shaft which drives the camshafts indirectly off the crankshaft has been a mainstay of the horizontally-opposed flat 6 engine utilized by Porsche. https://www.total911.com/technology-explained-intermediate-shaft/ https://www.oregonpca.org/wp-content/uploads/2014/06/ORPCA-IMS.pdf However you're correct that they do not have a the same IMS ball bearing the M96 non metzger engines have. The GT3 and Turbo have an internal oil fed plain bearing inside and that is where the idea for the IMS solution came from that Jake Raby invented and developed through LN Engineering.

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Actually, the new CEO realised that Porsches future relied on reducing costs by increasing quality (as defined by reduced defects in manufacture and less rework needed).  To do this he engaged a Japanese consultancy that had been formed by ex Toyota luminaries of the Toyota Production System to introduce Lean Engineering principles to Porsche. At the same time Porsche was running out of money - losing $150M in 1992 on only $1.3B in total sales - so they had to simplify and reduce production costs and this is why they went to one cylinder head design that could be used on both sides of the block.  The decision to adopt the same front structures on both the 996 and the Boxster is another example of this cost cutting. So I don't think anyone can blame the Japanese for the IMS issue, that surely has to lay at the feet of Porsche. In fact it was only through Lean that they were able to build the first perfect car on 27 July 1994.  By that I mean that every car they produced before this time had to be rectified in some way at the end of the production line before it was ready for sale.  (The company had been knowingly producing faulty cars on the production line and they had managed these faults by having an army of craft men waiting in a vast rectification area to reinspect and repair the problems hopefully before they got to the customers.) Porsche was so successful in adopting Lean that they ended up making money selling their gained knowledge to other companies.

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Is this info available freely Peter? I would like to know more about this "repaired in some way at the end of the production line before it was ready for sale"

Adam, Let me dig out a case study from one of my Lean textbooks that I will post here.  The Toyota connection gets raised enough here that I think there will be enough other anoraks around to be interested in it.

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Some Toyota Lean reading references below.  No idea if they have Porsche references.  Pre 996 cars were essentially hand build like you would do in your garage, but a little more organised.  996 onwards was a production line as you'd imagine it to be. Toyota's rigours in regards to lean principles is staggering but seriously who CBF with doing that all day long... The Toyota Way Fieldbook: a practical guide for implementing Toyota’s 4Ps Liker, J. K. and Meier, D. (2006).New York: McGraw-Hill Toyota Production System "One-by-One Confirmation" Kitano, Keynote Address. University of Kentucky, Lean Manufacturing Conference (May, 1997). Toyota Culture - The Heart and Soul of the Toyota Way Liker, J., Hoseus, M., and The Centre for Quality People and Organizations (2008), New York cGraw Hill

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Bugger!  It's a fair bit bigger than I recalled at 32 pages.  Its a chapter from: Lean Thinking: Banish Waste And Create Wealth In Your Corporation b y James P. Womack, & Daniel T. Jones that is specifically about the transformation at Porsche in the early 90's. If you and anyone else wants a PDF, just pm me your email address and I'm happy to send you a copy.

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Oh f#@k me, we are doing this stuff again at work, yes essential reading for anoraks and any budding six sigma aficionados!

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Ah got you now Pete. I thought you we're saying that LN IMS 'solution' was the one you would go for over the standard retrofit when you said solution. Bit of a roger victor clarance moment.

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Mike, Sorry I must be talking in riddles! Yes, the IMS Solution is the one I would go for because it solves the issue once and for all. However I accept that this product is sold at a cost premium and that sometimes we have to compromise and use one of the many cheaper but temporary ball or roller bearing retrofits on the market that will need to be replaced every so often.

6 years or 75,000kms for the LN dual row pro, less for the classic. LN also created a more economical roller bearing option but it's got a recommend lifespan of only 4 year.

What we have now, or very soon will, is a culture where everyone who buys a 996/ etc will replace the IMS bearing regardless as there is so much conflicting information out there and so many varying lengths of "repair". All for something that ultimately has a very low failure rate.... quite bemusing really!

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What a selling tool fear is! I bought into it, to each their own

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Just another example of how irrational we all are. Dan, Why would they be time limited? I can understand the km, but deterioration based on age?  Really?  I know of no other bearing that is replaced for that reason.

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It may seem bemusing, but a $2,000 fix to insure against a possible $20,000 + repair bill is a good investment in my opinion. Not that I intend to sell mine anytime soon but anyone looking to buy a 996 will surely give greater consideration to a car that has had the bearing replaced over one that hasn't. The IMS issue is also something that has made 996's an affordable option for many, and while the 996 will never see the stratospheric rise in value of air cooled cars, I believe they will again rise in value as people realise that they don't necessarily have to remain potential grenades especially C2 manual coupes as they seem to be harder to find than tip's and convertibles. I find it more bemusing that someone wouldn't remove a known potential risk of a $20,000+ repair bill for a $2000 preventative maintenance spend which would be even cheaper if it was done as part of a clutch replacement job. Just my opinion, but there is also a lot of value in peace of mind.

Original IMS bearing code marked on the seal is NSK 6204DUA17, so maybe they are still available.

I tried to purchase an original bearing from a couple of different bearing suppliers when i replaced mine but they were listed as not available to supply to other user meaning porsche have a licensing agreement for that particular part. Porsche don't sell the bearing separately either, they will only sell the complete IMS assembly for about $3500AU.

There are better solutions than the original anyway. Even the pelican IMS which is made by LN and cheaper than the IMS pro would be a better option than the original.

Agreed, if any component has a history of premature failure no matter how common or uncommon and there is a upgraded option available, you would be mad to use the original.

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Realised I've only given a partial answer. Even without considering the effect of torsion vibration, I think the lack of preloading on the IMS bearing is the biggest culprit.  It is Good Bearing Practice 101 to have the inner race axially loaded against the outer race to reduce ball skidding.  Usually this is done by spring loading with a wave washer for example or by shimming like in gearboxes. Often on double race bearings, each race is preloaded against each other to do this. Im now wondering if Porsche did that with the last larger dual race bearing revision and this is why these one are regarded as trouble free.  Pity no ones had to replace one so we could see!

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I'm wrong. They never "when to one cylinder head design [for the 996]" at all. Porsche had always used one cylinder head design for both sides of all 911's. Both sides of the 356's and even the 928! I should have said "Porsche continued to use one cylinder head design for both sides of the engine block as that's what they had always done so it shouldn't be a surprise they continued this engineering tradition with the 996."