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First Porsche, '02 C4S - Hello & Questions!

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Hi Everyone,


My name is Andy, based in Swansea, South Wales, UK. Having just bought my first Porsche (an '02 C4S) with 70K on the clock - I have been googling my little socks off looking at all things 996! I LOVE, LOVE, LOVE this car - never owned anything that goes round corners like it... the downside is, it keeps me lying awake worrying about it - but I think that's the usual new car paranoia, which will settle down!


Having found loads and loads of excellent posts written on this forum I decided to sign up, say hi and hopefully pick a few brains!


Currently, I am making myself extremely paranoid about the whole IMS issue! The reason for this is there is a little bit of oil at the base of the engine (eg the normal IMS / RMS leaky bit - according to images on the web). The leak is VERY, VERY slow (more just damp) and is not dripping or anything (have wiped, driven and nothing much more coming back down).


The question I have is this. There seems to be some discrepancy in information regarding leaks in this area. Some people seem to be suggesting that leaks in this area are NOT related to internal (eg potentially catastrophic) IMS issues as the "problem" bearing is actually sealed inside the engine behind the outer seal and therefore leaks from the outer seal are not relevant, they are just that, leaks from the outer seal and cause no damage, just irritation - and possibly the owner paying a bit more attention to oil levels!


Others seem to suggest that vibration caused by wear to the internal bearing cause the outer seal to leak, and therefore one SHOULD be worried.


Can anyone provide any clarification on this, should I panic / stop driving / do an oil change and check for metal / jump out the window / drive it like I stole it? In short, I don't want to waste a load of money if not necessary - are there any rules of thumb?


Incidentally, I'm not worried if it's just a very slow oil-leak from a seal I can deal with that in due course!


I'm sure this topic has been gone-over ad nauseum, so apologies, but can't seem to find definitive answers! (maybe because they don't exist!)


Best regards, all - and thanks!


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Welcome to the forum!

I suggest getting the history regarding pervious repairs, if any, regarding the IMS and RMS. Assuming you can not get or history is not available, I suggest pulling the oil filter and cutting open to check for metal specks. Using a black light will make it easier to see. If metal specks are present, I would have my car transported to and LN a Engineering

LN Engineering authorize IMS installer. Sorry for the break in reply...fat fingers.

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Thanks for the answers guys and sorry to bore everyone else to tears with what must be a done-to-death topic.


If anyone is interested, I called around a few specialist Porsche independents this am, finally speaking to two really, really nice and helpful chaps. One called Ollie from rpmtechnik and another called Simon from Cavendish Porsche, both really knew their stuff.


Both of them do the IMSB replacement work so could have easily scare-mongered me into panicking.


Ollie said he's been working on Porsches for 10 years and could count on one hand the number of IMS bearings actually collapsed and both said they were almost always on low-mileage cars.


Simon said he's been working on Porsches for 30 years and had seen 3 actually collapse. He also said, bore-scoring is MUCH more of an issue on the 996 that we should worry about, with repairs coming in at 4-5k and quite a lot of them, at that.


Simon's attitude was basically, don't worry about it (IMS), but if you're having your clutch done maybe look into getting it done for peace of mind. The leak is much more likely to be from RMS or even if it is from IMS (seal) it does not mean that you are likely about to have catastrophic IMS failure, also, the case bolts can leak down the threads etc. To be fair, I've never owned a 12 year old car that didn't seap a bit from somewhere!


Also, and very interestingly, Cavendish have stopped using LN IMS Bearings and sourced a much cheaper and "apparently" better swiss made alternative, which, to be clear, he wasn't hard selling me at all. If anything, he was suggesting that preventative measure for bore-scoring were much more important.


Furthermore and do NOT quote me  - ALLEGEDLY LN has been taken to court for two cases of their bearings collapsing?! (could just be hear-say) - I'm NOT stating that as fact, whatsoever.


I think, reading between the lines, the general feeling was that this was a hugely, hugely overhyped phenomenon - for *whatever* reason.


There was also a suggestion that a car at 70k miles or so was probably out of the "danger zone"...


I'm gonna get it done, if anything, to help me sell the car one day, but won't put the car on a back of a truck to get it there!


For anyone who's interested in the bore-scoring stuff "Waterless coolant" seems to be the magic ingredient. I suspect everyone already has this stuff and I'm preaching to the converted!


Hope this is of some use to somebody!




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First of all, welcome to RennTech :welcome:


I continue to be amazed at the inconsistent and often totally incorrect information being passed around as "fact".


With a quick search, you can turn up more information on the true level of problem the IMS caused.  Porsche recently settled a class action lawsuit which revealed that at its peak, IMS failures occurred in around 10% of the engines made during the time frame covered in the legal action.  As for cylinder liner scoring, yes, that also occurs, but has not proven to be as widespread or as catastrophic as the IMS issue.  When you have an engine start scoring a liner, it may go down on power slightly, or consume some oil, but it still runs.  When the IMS fails, the result is instantaneous death for the engine:


IMScasedamage.jpg  IMScylinderheaddamage.jpg


So when liner scoring occurs, you still have a running engine than can be repaired; when the IMS fails, you have a $20K boat anchor where your engine used to be.


As for alternative replacement bearings, consider that LN has more than 12,000 successful retrofits on the road; how many does this other company have?  After Charles Navarro and Jake Raby developed and perfected the retrofit procedure back in 2008, a lot of other companies jumped on the band wagon with their own "copy" kits.  Some are still around, others have been less successful, and their customer's ultimately "paid the price" for their lack of understanding and basic research into what works and what does not when it comes to IMS bearings.  There have actually been cases where some of these alternatives replaced a still fully functional factory IMS bearing, only to lead to pictures like those above, and the disappearance of the alternative supplier from the market.  So I would be very cautious when someone tells you that they have a cheaper alternative to the LN products that "are just as good".  The LN product is not an "off the shelf" unit, their bearings are made for them, and every component selected for their bearings has been tested to destruction to get the greatest durability and life expectancy.  


As for LN being sued, I am not aware of any case against them.  Over the years since the retrofit was introduced, there have been some dozen or so cases of LN IMS bearing failures, most of which were traced to improper installation techniques, or the LN bearing being installed into an engine that was already dying and full of metal shards which ultimately got into the new bearing.  Both Charles and Jake have been very forthcoming and open about these instances, and I am sure they would quickly respond to your inquiry concerning this question.  Both have websites of their own (Charles is at http://lnengineering.com/, Jake at http://flat6innovations.com/ ), and both regularly appear here as well in response to questions about these products and competitor's claim's.


As for "waterless coolant", I'm not all that sure about that either; the product strikes me as a solution looking for a problem to solve.  We see literally dozens of liquid cooled Porsches every day in the shop, some with over 200K miles on them, and not one of them are using this "magic ingredient" as you describe it, and none of them are dying from liner scoring.


To go back to your original question about your oil leak between the transmission and engine cases, it could be either the RMS or the IMS; both are well known to leak.  But if you have a leak in that area, it is not going to get better, and things could get considerably worse if it is not addressed.  Regardless of where the oil is coming from, over time it is going to both ruin you clutch and potentially degrade the elastomer in your dual mass flywheel.  While the pressure plate and disc are relatively cheap by comparison, the flywheel is not and could easily set you back the better part of $1K (US) just to buy it.  On the other hand, if you took the car apart now and repaired the leak(s), you could still be able to salvage your current flywheel; and you would have the opportunity to retrofit you IMS at the same time, ending all of your concerns in one move.  Just a thought.............

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Like you, new to Porsche.  I bought my 02 C4 Cab about 15 months ago and have used as a daily driver as well as 6 days at the track lapping with other sport drivers.  Love the car, loose sleep over the IMS, will have replaced this winter when I do planned preventive maintenance on my clutch and air-oil separator.  


I've done more research than I care to think about and candidly all roads lead to replace IMS, use LN Engineering Bearing and use certified shop.  


Hope this helps and happy driving.

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Thanks for the great and detailed answer JFP! I can see this issue is a very contentious one. BTW I have no interest in p***ing people off whatsoever, it's more just of academic interest really. I did a philosophy degree, :-) ....

Edited by herogenous
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Thanks for the great and detailed answer JFP! I can see this issue is a very contentious one. BTW I have no interest in p***ing people off whatsoever, it's more just of academic interest really. I did a philosophy degree, :-) ....


Sorry if this is all boring and if you're all sick to death of IMSB, do please ignore! :-)


Incidentally your advice is very sound and logical - my plan is definitely to get this taken care of asap and I suspect it may well be with the LN bearing.


Incidentally, here is some more food for comment for anyone who cares! -  Just to be clear, I do not have an opinion on this whatsoever, I'm just seeking whatever "truth" is out there and the opinions of others.


One Porsche Specialist said that they had taken the original IMS bearing to a bearing design specialist in the UK who said it was pretty much just a standard bearing that might be used in many different applications. The replacement he was suggesting was just a much higher quality ceramic style bearing (I believe suggested by the same bearing expert) with a much higher load capacity etc, it seemed to make good sense to me, but then... what do I know!?


It would seem to me that replacing an average bearing with a (max?) failure rate of 10% with one of a much, much, higher load capacity / quality & hardness would, alone, result in a far lower chance of failure? Is this flawed logic? Is there something fundamentally different about an LN bearing than for example a very well made ceramic bearing from a different company. (NOT BAITING here.. genuine question.)


Also, is there any evidence to suggest that the cars that failed were a "bad" batch of bearings - created on Christmas eve or something... and that by now, most are already dead, with a few still surviving in perhaps low-mileage cars - or does the time period over which the problem stems totally preclude this?


Regards all!



The bearing LN designed was a long development process, during which literally every component and material was not only examined, but actually tested before LN settled on the current ceramic hybrid design.  The issues involved not only strength or hardness of the ceramic balls, but how they interact with the cage and races use to hold it together.  A lot of different ideas were tried, many were rejected along the way before the final design was settled.  As I noted earlier, these units are not "off the shelf" bearings used for other purposes, they are built for LN, to their specs, so no one else has the exact same bearing.


Also as noted earlier, the bearings that failed fell into two categories, they were either installed improperly, or were installed in engine's that already had other issues and should have not even been considered for a retrofit.  To my knowledge, there was nothing wrong with the bearings themselves.  Because of these problems, LN moved away from selling the bearings directly to the end user's (DIY market) and moved to a more elaborate program that requires professional installers to be trained on how to qualify the engine before even attempting the retrofit, as well as how to properly install the unit.


Do some internet searching, there have been many threads involving both Jake and Charles on this subject.

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Thanks JFP.. I guess purpose built has got to be better really!


Thanks for your patience with the newb q's - I think I'm on about 24 hours of solid google research now... my brain has melted.. hope the engine doesn't!




Not a problem, that is what Renntech is here for.  And don't consider this to be an overly contentious issue; while it can be so with some individuals,  it is more one fraught with misinformation, innuendo, and rumor that are masquerading as fact.  But if you do your homework, "the truth shall be known."

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  • 2 weeks later...

Upgraded to the latest and greatest LN Single to Dual row bearing, installed the lower temp thermostat as per your advice JFP! Cheers!


At some point in the future may well consider the waterless coolant just for good measure - seems to be gaining quite a lot of positive traction (in the uk at least!) Opinions seem to vary quite a lot this side of the pond on various issues!

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