Anyone worried about IMS? In situ solution.

Now available in the UK. Anyone who has an interest in IMS, has probably stumbled across LN Engineering in the US and their preventative IMS upgrade. http://www.lnengineering.com/ims.html They offer new and additional bearings, flange and seals. Autofarm have now won the exclusive rights for the UK. The upgrade can be done without engine out (unless 4WD) and with a new clutch can be fitted for £1,550+VAT. http://www.autofarm.co.uk/engines/water_cooled/shaft_tech2

Interesting, especially how different oils can help minimize the risk and why driving it properly is recommended

I had this done on my Boxster after a 'routine' RMS change brought to light a snapped bolt on the intermediate shaft bearing housing: Luckily no engine damage done, ordered the bits from the USA and had the OPC pull out the old bearing and hammer the new one and bolt in. Seemed to work a treat. Don't know if I'd want to do this as preventative maintenance though, from what I understand it's a pretty brutal process.

Just to add that we at Hartech also offer the same services but have a diferent but perfectly reliable and succesful replacement bearing and spindle etc and can carry out the job with the engine in. The differences in our solution are mainly in the choice of bearing and have been well reported on many forums and are guaranteed. However our prices are £400 less across the board than those quoted by the Autofarm web site. Our price for a 996 manual to change the IMS bearing for an upgraded version is therefore £800 + vat (and includes oil change, new filter, new bearing and sipndle and a new RMS). We also have special tools manufactured to protect the parts as we diss-assemble the old bearing and re-assemble the new one etc. With a new clutch is therefore as above but includes the clutch and pressure plate etc and is £1150 + Vat. We add £150 + Vat for tiptronic. These prices do not reflect any particular criticism of anyone else, as both Autofarm and ourselves repair engines for these models as well - but I guess the main difference reflects our lower charge out rates here in the North West as I have often said we could not offer these prices either - if we were located further South. So - good for owners living up here and not such a difference for owners down South who have to factor in the distance and inconvenience of coming up here. Baz

I was not aware of that, and I only posted the Autofarm details as I had researched LN Engineering's solution and was originally disappointed that it was US only before Autofarm recently "imported" it. I do not have any personal interest in the Autofarm solution. Do you have details on the process and upgraded parts etc your method involves? Also, what is the premium for C4s? (+clutch+RMS) Is it engine out again? :sad: Thanks.

Since the question has been asked - here are some cobbled together extracts from other postings on the subject that contain a lot of technical information about the problem and our solution. Because I DON'T HAVE TIME TO EDIT THE CONTENT IT MAY REPEAT DETAILS A BIT SORRY! The positioning of the intermediate shaft long ways is maintained by the bearing press fit. Although it has a small wire circlip in a groove but this can be overcome to remove the bearing by shock loading and it is mainly the interference fit that holds it in place (the clip later changed to a circlip). New bearings arrived for assembly with grease inside and seals on both outsides. There is no way for oil to pass in or out of the bearing initially. While grease is OK for lubrication at the loads I have calculated and the revs - a heavy interference fit on both the inside and the outside of the bearing results in the balls inside grinding some minute particles of metal away as they "run in". I think everyone knows that when running in you usually have to change oil to remove those initial wear particles while an engine settles in - but there is no way this happens in this bearing - which is perfectly adequate for the loads applied to it - given sensible lubrication so IMHO a more expensive bearing is not neccessary (just the right spec and clearance) and we have had none fail in years of modifying and replacing them and to three figure numbers. We do not fit seals because with fresh oil being thrown in the direction of this bearing by the two chains nearby running in an oil bath in the sump area - at up to 40mph - there is plenty of potential lubrication available and as the ball tracks are hollow there would always be sufficient oil sat in the bottom of the groove to accommodate initial start up – and now fresh clean oil will be present. Some we have replaced early have a mixture of grease and oil and what looks like grinding paste inside the bearing and with two ball tracks in the earlier bearing the amount is - suprisingly large. The single row bearing specs up slightly better than the double row because the double row has less deep ball tracks – so the replacement is actually probably better and of course half the metallic particles to wear away. There is also no cooling since no oil flows in or out. It seems to me that some are tighter than others (normal mix of manufacturing tolerances will allow a small number to have the tightest fit on both inside and outside while most are less tight) and of course some will run hotter than others while manufacturing tolerances will result in some actual bearings needing more running in (and creating more metal particles) than others. Most survive until the seal wears and allows some oil in which mixes with the grease forming a type of grinding paste and later on as the seal edge suffers it washes some grease and particles out and eventually works more like the seal was not there in the first place. How soon this happens is again a function of the tolerances and use. Therefore some - once they get past say 50K or so – generally improve and therefore last a long time (the loads are low - the other end of the shaft which has one chain running against it s just a steel diameter in an alloy hole). We have seen some in which the ball cage has cracked and although the balls rotate in the same direction – when they crowd together the face of the balls runs in the opposite direction to the next ball so the surface of the balls run against each other at twice the speed that the balls are rotating at and wear rates increase dramatically increasing wear particles. Others have actually cracked the outer bearing housing through metal fatigue (clearly marked) implying that they simply ran too tight for too long or the lack of a cage and the balls crowding over one side of the track overloads the outer race. Because the spindle is such a basically poor design with a very weak centre - this then often snaps. By removing the seals - most bearings should be OK since the grease is quickly replaced by the oil and the wear particles can escape and be collected by the magnet or filter. However while removing the bearing in situ is possible (and we have a tool to do so safely) replacing it strains the weak original spindle and could cause a fatigue crack initiation - so a stronger design of spindle should be used to reassemble it. It is also necessary to take off both chain tensioners to avoid the chain load forcing the IMS over too much to one side and expecting the spindle and housing to force it back against the hydraulic tensioners. This obviously takes longer. We also change oil and filter at the same time and usually the RMS. In my view there was nothing wrong with the idea of an IMS - only the basic engineering thinking was flawed - but then only enough to fail in very small numbers statistically - so not an absolute disaster. What amazes me more than anything else however is how simple the IMS problem was to analyse and fix and how long it remained a weak spot despite several re-designs - none of which addressed the obvious cause - the need for a tight fit and the lack of proper lubrication resulting from the seals. By repairing them for those that cannot afford a new engine - we actually IMHO help preserve the confidence of owners and the reputation and value of the cars. We mainly deal with cars over 4 years old and so have to deal with owners with generally smaller financial resources – than those buying brand new cars and changing every three years. To do that better than anyone else we introduced our Lifetime Maintenance Plan 10 years ago (well ahead of the market) and invested in engineering solutions, equipment, space and staff - to enable less well off owners to afford to keep their cars - even if and when they become one of the small in number whose experience is devastated by a failure that could have so easily been avoided. There is no other UK business offering anything like as comprehensive a warranty, nor anything like the quality and variety of repair solutions or the ability and willingness to adjust rebuilds to suit the pocket and future intentions of the owner. I did contact the manufacturer to buy replacement bearings – which were out of production but in the course of the conversation they confirmed that they too do not understand why Porsche sealed the bearing and recommended they did not. Furthermore- any engineer who is familiar with engines will know that a grease filled bearing inside an engine will gradually lose its grease and then run on the oil. The debris trapped inside and mixed with the grease initially and with old oil later on – prematurely wears the seal edges to allow the grease/sludge to seep out and new oil to seep in and then sit there. We have seen a failure of a later M97 engine IMS but it is rare – however a larger bearing will resist contracting as much under an interference fit and has more space for more grease and for more contaminants to spread. Similarly we have seen the gearbox bearings (which are also sealed) fail. I do not expect every IMS bearing to fail and I don't think that this failure is related to use or even servicing and I believe it is entirely random for the good engineering reasons I previously stated about the quality of the bearing and the build- up of tolerances and have even explained why after say 50K they become more reliable again.. The bearing is a sealed for life bearing but they are not sealed for life when running in hot oil and that is the mistake IMHO. Indeed when you remove the bearing some very black old oil mixed with metal particles slowly drips out of the IMS tube in which it was trapped on the inside of the seal and bearing. On inspection of those within the danger zone – some lower mileage ones have a mixture of old oil and grease and metallic particles like a grinding paste inside, older ones just have old oil and particles and very old ones have just old oil left. Clearly oil slowly ingresses and mixes first with the grease and particles and later washes the grease away just remaining as old oil mixed with particles. A heavy interference fit will inevitably vary from part to part as will the fit and quality of the bearings – so some have a build up of poor quality and tight fit while others may be of better quality and a loser fit – most somewhere in the middle. Some will be run in slowly and others more aggressively and oil changes may be more or less frequent. We simply don't know if this has any influence or not but out if it all some fail and most do not. It is a marginal design and removing the seal and allowing fresh oil to wash out the running in particles and keep it cool and properly lubricated – is the best improvement. I have wondered if the seal is to protect bearings and pre-assembled components lining up for mass production – but it should have been removed on assembly. Numbers are however minute – it is not such a big technical failing – so therefore – to come back to exactly where I started from – my advice is just get some cover that you can afford to protect you from the cost of a failure – just like you do for house insurance and car theft etc. Eventually all the grease has mixed with the oil and become entrapped in the tube leaving very old oil mixed with bits of metal trying to lubricate the now prematurely worn bearing with minute spots of new fresh oil gradually seeping in. Once a new bearing has been fitted without a seal (of whatever type and quality) I would always promote the best oil you can afford and more importantly changing it often. My only argument is that I don't see changing oil quality making any difference if the original bearing and seals are still in place because the problem mix that is already trapped within the bearing as it came from the factory is still in there and if you are going to take it to bits to clean it you may as well change the bearing and leave out the seal - after which I believe std oil types are perfectly OK.. A better quality product is always better than a lower quality one but more expensive and if it is unnecessary the extra cost is wasted. The question is always - is it necessary to fulfil the function. In my view and engineering experience and the evidence of those we have repaired – the std replacement bearing of the right grade fitted with the stronger spindle is perfectly up to the job, has proven to be OK and we guarantee it anyway. The problem was never the specification of the bearing but was the insistence of fitting it with seals that appear to have actually caused the problem in the first place. All parts are made to minutely different sizes and inevitably sometimes you get the largest pin going in the smallest bearing hole in which the inner track is big and the outer track small with the biggest balls in it and fitting into a housing that is the smallest. The odds against it all working one way are huge and therefore the number of "tight" fits is low - but it does happen and likely to present more of a running in problem and more debris to contend with. The amount of grease in there also probably varies - all leading to a small number of failures simply because the design is IMHO marginal. Bearings are available in a variety of fits or tightnesses and when an interference fit is in use the designer should chose the right one for the application. We have made our choice and we find it works OK. I will try and attach some photos but if they do not appear and someone sends me an E-mail address who can display them I will send them on to them. Baz

Sorry - forgot this answer - The premium for a C4S is just £100 + Vat Baz

Where is the seal that shouldn't be? Can this be removed at, say, the same time as clutch / RMS change? Ie can you improve the lubrication for nothing, or is it burried deep?

Yes you can remove the seal but to do so you have to drop the oil, set the crankshaft at the tdc position - remove the hydraulic tensioners (2) and that is difficult and needs special tools. Then you undo the nut and prize out the three pronged housing finally - with a pointed scriber say - prizng the outer seal out. Tp put it all back you need a stronger spindle because to get the housing back in it hits the crankcase at the same moment that it fits over the spindle thread and the weight of the chains etc means you have to force it over to get the housing back in and as it has such a small recessed diameter this could crack it. It is little more work to remove the old bearing and replace the spindle (if you have gone this far). Baz

Cheers.

Nice work Baz :thumb:

Great news for those IMS probs, Keep up the good work lads.

Just one final point before I get the usual arguments about what bearing is best and why we think the std type bearing is OK if properly lubricated and that it doesn't need an more expensive bearing - I offer the following. Not only does it spec out perfectly OK and not only has experinece shown it to be perfectly OK - but from sheer common sense - it 95% or 98% of the cars fitted with the std bearing run perfectly OK for their whole life cycle (which is statistically about right I think) - despite having the great dissadvantage of the problems of trapped grease and metal particles, then old oil and no oil replenishing system etc etc - always running in very old trapped oil and crap - and every one we remove had trapped old horrible sludgy oil inside mixed with metal bits - but still 95% or 98% survive perfectly OK - is it difficult to imagine that a new specially selected version of that bearing, spending its whole life properly running in a fresh oil bath and having runing in wear particles removed imediately and trapped by the magnet and filter and having fresh oil thrown at it at huge velocity - and running round a spindle twice the original cross section - will be perfectly OK.! If the original bearing spec was so bad that it needed a much more expensive bearing - 95% to 98% would never survive the original assembly with seals both sides - which are the problem with the design. Baz

Hello Baz, as an apprentice engineer from the seventies with much experience I have to say that you make absolute sense and if I were nearer to you I would most certainly let you have my C4s for all its work on your lifetime plan. My one concern is for your health, you must be a workaholic to be able to post so much on the Porsche forums, which I have to say are very informative and most reassuring to all of us. Thankyou. Mike Brown

Thanks for those kind words Mike. Actually when I started my first motorcycle racing engine/gearbox business I made a big mistake by allowing it to grow with me learning to be the accountant, designer, advertiser, foreman, planner, machinist etc etc. It is a common mistake for small business owners to make because there comes a time - as it grows - when the owner cannot cope but there is no one else with the background or experience of running the business - to help. It is the main reason I accepted an offer to sell it to a plc although its value was seriously handicapped by that lack of middle management support. Knowing that - and after working elsewhere for several years - it has always been a main principle of this business that we gradually develop all our staff to move up and take over various roles - while I initially oversee their contribution and eventually leave it to them to learn and develop. One employee (for example) - started as a Saturday boy and worked right through to a degree in automitive engineering and now is our workshop manager (and destined for more). We now have three degree level employees and several more on that road. So I have now got to the stage where I am no longer needed much for the day to day running of the business and instead concentrate on design and development, long term financial planning and responding to the Internet - which is therefore - not too tiring although I type fast and make lots of spelling mistakes (as most forums don't have a spell checker). So don't worry about me - I am OK and looking forward to the future in which I will be increasngly involved in racing development and competition - in a way - back to where I started from - but with cars not motorbikes this time. This inew involvement meanwhile is helping the staff learn and understand more and more but in a competitive environment. They say you go back to your childhood just before senility - so I seem to be on that road! Baz