Oil leak............again and again

Ok, after some thoughts on the issue I have.... 996 C4S had an amount of oil in the usual places when I bought the car. When the clutch was replaced, the guys at Dovehouse (who I would thoroughly recommend to anybody) replaced the Rear Main Seal and Intermediate Shaft Seal. All was fine. After a couple of months the oil had returned (covered a couple of hundred miles). Dovehouse took the gearbox back out and replaced the seal under warranty. The car has just been in for new coffin arms, control arms and track rod ends. The oil is back and I asked Dovehouse to have a look. They are pretty confident the seal is right this time (the last one was a faulty part, not their workmanship) andwill take the gearbox back out to check the seal and will replace if it is faulty. If however the seal isnt faulty I could have a more sinister problem on my hands? In other people's experience, where else could the oil be from if it isn't the RMS? 1. Imternediate Shaft bearing letting oil by - about to give up? 2. Porous crank casing? 3. Other? Thoughts and experiences appreciated. The car has 94k miles, full service history, no expense spared, everything else is perfect - just the niggling "what-if" with the golden drip!!!

Could be the IMS bearing that is worn and running out of round which would then wear the seal and cause a leak. Clearly it's booking in and will be sorted (I guess).

What sort of mileage have the IMS bearings failed at? Is there a pattern? I'm sure DH would've picked up excess oil from this area when they replaced the RMS? It's a gamble really - If I ask them to take the box off to check the seals then is it best to have the bearing done as a matter of course or is there a lot of scaremongering? Is it plausable for the RMS to fail twice in a matter of 2k miles?

If anyone remembers Scouser, he had about 7 RMS seals replaced before they finally got it sorted..... Another thing that can cause a drip of oil are the crankcase bolts around the RMS/IMS area. There is a technical bulletin which says they should be replaced when changing the RMS and Intermediate Shaft support post seal. I very much doubt that the IMS bearing is running out of round. It would have caused a leak long before now. The IMSS is sealing the support post for the bearing, so even if the bearing was out of true, it shouldn't cause a leak on the support post seal.

Richard, The car had a weep when I bought it - would this (likely) have been the RMS all along or could it be something else? Is it worth getting the IMSB replaced now or would it have gone before now? Is there any pattern with them? Obviously each car is different depending on age, mileage, etc. etc. I assume when the gearbox and flywheel are removed, if the RMS is leaking the visual will be obvious? There would be a degree of movement in the IMS if the bearing were on it's way out and evidence of leakage from this area if the IMSS was faulty? Could there be anything more sinister than the above or a porous crank case?

I suspect that the weep you had when you bought it would have been the RMS. It is such a common issue that it is the most likely cause. There is no real pattern to Intermediate Shaft bearing failures, although there is a school of thought that if they are going to fail, it is likely they go sooner, rather than later. The main problem with the bearing is that it is a sealed bearing. (Not to be confused with the support post seal). Why Porsche used a sealed bearing in this application is a matter for debate. Most experts consider that an open cage bearing would have been more appropriate. The bearing is below the surface of the oil in the sump, and would be properly lubricated by the engine oil and mist. I subscribe to the school of thought that the seals deteriorate over time, and the engine oil can get into the bearing. If it was me, I would have left it alone and lived with the drip until the clutch needed changing. RMSs tend to drip for years without getting substantially worse. I've never heard of one turning into a gush. At 122k I might have considered changing the bearing while the clutch was being done, as the majority of the cost is in the labour to get to it. I personally wouldn't use the hybrid ceramic bearing, but the standard one with the outer seal removed. Yes, it may obvious where the oil is coming from when you remove the flywheel, but as I said, the bolts for the crankcase and IMS support post should also be changed, as they can also leak, and it can be confused with an RMS leak. The first time it was done would be more difficult to detect, but the second time would be more obvious as they should have cleaned the area first time. They might have been able to feel for play in the bearing once the support post had been removed, but unless there was a lot, it would be difficult to tell. Just my 2p's worth.

Bit more than 2p's worth Richard Really helpful for Us guys who know cars but don't necessarily know these magnificent animal Thanks

Sorry, Richard, I might've confused the issue. The RMS and IMSS were done when the clutch was replaced. RMS was done again under warranty a couple of weeks later. It's now leaking again but without splitting the box again there is no way of telling if the culprit is the RMS. If DH take the box off and it's RMS then they will do again. If it isn't I've got the box off (which I will then be paying for) so should I replace the IMS bearing to be safe? You can only offer advice I appreciate but would you - Run the risk of leaving it? - Let DH take the box off and if it is RMS then let them change it again - As above but have the IMS bearing done at the same time.

Did they replace the Bolts as RichardH suggests You will not be able to find out till Monday

If it is just the odd drip, I don't think there is much of a risk if you just leave it. I get your point about DH doing it again - you take the risk of paying if it isn't the RMS or IMSS. Apart from the bolts I have mentioned (which should be changed when doing the job) there can't be anything else in that location causing a drip. A porous casing is highly unlikely - I've never heard of one on these engines. As for the bearing replacement it is a tough call to make. What bearing do DH normally use? If it is the hybrid ceramic bearing, bear in mind that LN say they should be changed as per the email below, when I asked the question of them. The other replacement units (from Pelican Parts, etc) are generally sealed bearings, so you could end up creating the original conditions. I think I would ask Hartech what type of bearing they use, and if it is sealed or not. If you decide to replace it, I would use the same type of bearing as them. They are probably the best in the business for M96 rebuilds, and are very approachable. -------------------------------------------------------------------------------------------- From: Tammy E. Hellings [mailto:[email removed]] Sent: 09 January 2013 20:03 To: Richard Hamilton Subject: RE: Ceramic Bearing Life Hello Richard, Thank you for the inquiry. We recommend it as a service item every 4 years or 50,000 miles. Sincerely, Tammy E. Hellings LN Engineering

I can absolutely guarantee Tony at DH replaced the bolts...... When I booked mine in several years ago, he took the time to get a diagram up on screen to explain ALL what is required & in fact it was leaking from the bolts & not RMS/IMS...... Suspiciously, it had been smeared with silicone in an attempt to cure a leak & prior to my ownership had only been serviced by an OPC to which I have ALL receipts...... Trust me, it had been meticulously maintained..... hth Paul

When i had a new 996 4 S it had 3 rear main oils seals go in 3 years 1 at 6k 2nd at 10k and 3rd at 12k all done under warranty So going back as the car was a 2003 model i was on seal upgrade no 8 at the time god knows what they are up to now. Porsche said if it goes again they would have the engine apart to look at the problem in more depth. I never got that far I sold it shortly after the 3rd rear main seal was done. I know some mist but mine was was leaking onto the floor the last time a huge puddle. enough was enough it had to go. Cheers Cliff

I can't imagine Tony, Phil or any of the guys at DH missing anything at all. I trust them 110% with my car. I think for the sake of sanity I need to have the box out again. If it is the RMS or IMSS then all good, I'll get them to check the bearing as well though. Is there anything else it 'could' be?

I'm sure Tony opens old oil filters for any signs of 'metal', which may indicate an impending failure...... perhaps speak to him & ask if he done it with yours at any recent service... Very frustrating when you can't nail down the cause.... Hope it's sorted at reasonable cost.... as you've said, trust them 110%

;-) Me too, I thought they'd never get it right. If memory serves me right they finally admitted to using the wrong RMS on mine.

Silicone LOL your not the only one Porsche techs did that too.

Glad to hear I'm not the only one..... silicone v 3 bolts, what costs are they saving after removing gearbox anyway? DH didn't do servicing when I purchased my car from them but it goes there now...... & I love the drive there to[ ]

Hi All - I've just taken my 2004 996 C4S (67,000 miles) in for repair for an oil leak that occurred in the last week or so. To my immense relief, it is the Chain Tensioner bolt .. or rather the washer it sits on that appears to have corroded. So, pence for the part but about an hour for the labour since the crank has to be set at TDC and care taken not to let the timing chain slip a notch. There are two visible Chain Tensioners - one is vertical one and looks like a sump plug (but isn't), clearly visible if you look under the engine from the back on the LH side. The other one is horizontal and on the other side of the engine and harder to see without ramps. My leaky one was the vertical (LH from the back) one that tensions one of the IMS chains. Apparently, this is quite common fault and after 10 years of use you have to expect these things. Although it is a very small leak, under heat and pressure it has blown a lot of oil onto the exhaust and the smell was the first thing I noticed. I reckon it dribbled a litre of oil out before I got it to the PSC in Byfleet. If they find anything more sinister I'll report back but I'm hoping to be back on the road in a day or so. Phil T PS. Picked it up today and the bill was £130 - many thanks Porsche Byfleet ! I'm very pleased. 2004 996 C4S Silver, Black Leather

OK, a further update. I drove the car to the station for a couple of days as the other halves car was in for a service and she was using our main car. All was fine with the drip while I was using the car and for a couple of days afterwards. I've just spent a week in Mexico and checked the underneath of the car this morning and there is a significant puddle. Could this be something to do with the fact that the car isn't being used regularly or does it help define what the actual problem is? Extremely frustrating!

Right! An update and (hopefully) some closure. DoveHouse had the car on Wednesday and allowed me to view the full process from start to finish so I knew exactly what was being seen by them. We then chatted through the options stage by stage as to possible diagnosis and cure. They dropped the gearbox to expose the back of the engine. This is what we saw......... The oil is concentrated around the IMSS and the nut. You cab see where the flywheel has flicked it up with rotation to the right hand side. The RMS was bone dry....... The whole area was then cleaned and dried fully. Phil applied a very sensitive leak detection spray and then ran the engine at 2500rpm for 45 minutes with my permission. This created around 3bar or pressure in the engine casing. While it wasn't quite road conditions with cornering, gear changes etc. it was as close as we could get without putting the box back in, runing around for an hour and then taking it out again. The result below wasn't overly conclusivebut you can see how sensitive the spray is as there is yellowing where the residue was from before. We had hoped to see a lot of oil around the IMSS. After this I asked Phil to remove the existing IMSS to see if it was damaged at all. As it turns out it wasn't but there was a slight play in the IMSB. After discussion we decided that this very slight play, along with gear changes and added pressures when driving could result in oil bypass. Owing to the fact that there was no damage to the RMS or the IMSS at this point I was paying the bill. I opted for an LN Bearing upgrade which the guys did me a very good deal on, along with the labour to extract and fit as I was already paying for the gearbox etc. Bearing installed, nuts and bolts sealed and installed with locktite. While there was no 100% conclusive evidence that the issue was the IMSB, I now have peace of mind that I have a new bearing, the RMS isn't leakign and I don't have a porous crank case! If it does weep again then it is one of the seals if they decide to go again. Topping up with oil is better than a new engine in my opinion! I also see the new bearing as an investment in the car's future. Huge thanks to Phil, Tony and all the team at DoveHouse for their honest advice, great customer relations and for letting me work from there all day!!

Even though it was expensive, let's hope it is an end to the leak, and you have some peace of mind with the ceramic bearing. They don't seem to have been the problem, but the bolts I showed in my earlier post don't seem to have been changed in your first photo.

Personally I would have not gone down the ceramic bearing route - too much smoke and mirrors (not to mention cost).

Rich, The bolts were replaced this time and I can only assume they were the last? With regards the upgrade being expensive, yes you are right but there was an amount of play with the existing one. I'd rather be safe than sorry and have added peace of mind. Also, the next owner, if she has one, will also have the same.....

Unfortunately the ceramic bearing is limited life and they seem very vague about numbers fitted and more importantly, numbers that fail. A new standard bearing has a real advantage but your money and your call. Personally I would avoid a car with a ceramic bearing based on my first comments in this post.

A lot of research was carried out beforehand and ultimately I'm happy with the decision. I have a more robust bearing and cover around 4k a year. Each to their own I suppose. We shall see, if anything else comes of it I'll let you know!

Can you tell me the real advantage of a steel bearing opposed to a Ceramic then, because Ceramic is much harder than steel and Ceramic bearings typically last much much longer than steel?.

For whatever reason LN have lifed these bearings. It may be that the bearings are better than the steels but they want to cover their backs. It may be they've tested them and they don't last as long as the steels. We don't know. The steel OEM items fail at a rate of less than 5% (plenty of data to support this), and anecdotally if they don't fail early on they're less likely to fail. So that's the choice you're given.

Knowing LN we will see them for sale once they have cleared their stock of steel bearings.

Advantages? Cost is the big one and no associated 'smoke and mirrors'. I am always suspicious of scaremongering and associated solutions from those who have a vested interest and the perfect product to fix it. As regards the life of the ceramic 'solution' - it's not a true lifetime part and it is VERY conditional in it's claims:- Service interval recommendations are valid only with use of Joe Gibbs BR break in oil during the new IMS bearing break-in period of 200-400 miles along with use of an LN Engineering Spin-On Oil Filter Adapter with subsequent oil changes at 6 months or 5,000 miles using Joe Gibbs DT40. As I said earlier - personal choice but personally I would avoid a car fitted with one.

But buying a second hand car with a ceramic bearing already fitted you wouldn't be paying for it? Therefore I fail to see why anyone would walk away from a car fitted with a Ceramic Bearing anyone knows ceramic is harder than steel and everyone has fallen foul to 996 scaremongering. Of course if you have a spin on oil filter adapter from (LN Engineering) your car will never break.

Goes back to my point. The part is lifed. So you buy a used car with an LN bearing with say 1,000 miles left on the clock. Do you bin it at the end of its life (thus paying for it again and the silly service/break in requirements) or just assume it'll go on forever - which the company itself does not claim.

And that would be falling foul to scaremongering mindset.

The original bearing was lifed - the majority remain perfectly serviceable.

Thankfully, my DFI-engined Cayman isn't affected but the whole RMS/IMS issue and it's engineering solutions are of interest to me. Like Richard H, I think that immersing a sealed bearing in engine oil is asking for trouble but I'm sure Porsche had their reasons. From memory, I believe that the air-cooled and Mezger engines used the same arrangement, but they were proper dry-sumped engines which avoided [total?] immersion of the bearing, and the IMS set-up allowed Porsche to use identical left and right-hand cylinder blocks to reduce costs. I presume that a ball-race bearing is used to take the end thrust, the other IMS bearing being just a plain bearing lubricated by engine oil, so why Porsche didn't use pressure lubrication for the front bearing is a mystery to me and note that this is one after-market solution. Here's an interesting summary from a The Popular Mechanic tech day on the subject: http://www.thepopularmechanic.com/PorscheIMSOptions.html Note that with the exception of the direct oil feed solutions, all the other solutions were considered to be "lifed", but I would consider any part of an engine to come under this category. After all, Porsche only warranted a new 9x6 for 2-years [or 40,000 miles?] back then. I just hope that Mark's solution gives him long-term reliability and confidence to drive his car without concern over the issue. Jeff

http://rennlist.com/forums/996-forum/869599-ln-engineering-ceramic-ims-bearing-failure-at-30k-miles.html That might pan out interesting? Looks to me like because as I said Ceramic is so hard its worn out the race. I personally reckon all the bearings come from China at a $$$ mark up because they cost pennies.

I would not assume that it would last forever - the post above being indicative. I have no real confidence in the 'solution' that the ceramic bearing is claiming to be offering - personally I think using one as an IMS bearing is the wrong application for that design of bearing (personal 'old engineer's' view). Because of this I would not buy a car fitted with one as it provides no piece of mind to me whatsoever, in fact less so than a car with a conventional bearing.

Chris, The bearing needed to be replaced so I took the decision to go for a the ceramic option from LN on the advice of DoveHouse who have seen bearing failure. They have also fitted a number of the LN bearings. I trust them, it is what I pay them for. If the original bearing is a servicable part then I agree that the LN bearing should also be servicable. If it is at 40k then I have no issue. The car does around 3k per year so I have another 13 years before I need to worry about it. You obviously don't like the solution, I myself am happy with it, as are a number of other people. Each to their own.

But there is no confidence in any is there? no proven or disproved part?. As for bearing type application surely roller would have been more appropriate, But Ive not made my own bearing and cashed in yet. LN bearing submission is a serviceable part @50k But there's cars with three times that on the OEM bearings? So many companies have cashed in on the scaremongering and the few mis fortunate 5% engines that have gone pop. Yet I have never heard a company/ Garage making diagnoses based on un questionable results from bearing harmonics and vibration tests?. We have retrofit bearing suppliers that come up with numerous after market bearings? well that doesn't give me much faith in there products and obviously neither do they. All I see is ££££... All we have to thank these companies for is a massive depreciation in the price of 996's and lots and lots of Internet forum Bandwidth traffic. Still could be worse, could have a LOTUS badge on it.

Hi Mark - I was not being critical of your situation or ultimate choice, more about the whole issue in general. The whole ceramic bearing thing has smacked of 'snake oil' from day one to me and clearly I might be in a minority but then I have no vested interest in selling or fitting them and any opinions I have make no money for me. Since there are no failure stats that could be considered impartial for the ceramic bearings I think your prediction is optimistic to say the least. Hope it last many years sir - just drive and enjoy!.

Morning guys , really interesting thread, just ordered the bolts as recommended ! top tip , thanks