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

markrwadsworth · Feb 27, 2015

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!!!

Chris_in_the_UK · Feb 27, 2015

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).

markrwadsworth · Feb 27, 2015

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?

Richard_Hamilton · Feb 27, 2015

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.

markrwadsworth · Feb 27, 2015

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?

Richard_Hamilton · Feb 28, 2015

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.

richardjjs1 · Feb 28, 2015

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

Thanks

markrwadsworth · Feb 28, 2015

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.

richardjjs1 · Feb 28, 2015

Did they replace the Bolts as RichardH suggests

You will not be able to find out till Monday

Richard_Hamilton · Feb 28, 2015

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:xxxxxxx@lnengineering.com]
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

kasspa · Feb 28, 2015

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

CLIFFWILKINS · Feb 28, 2015

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

markrwadsworth · Feb 28, 2015

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?

kasspa · Feb 28, 2015

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%

thirteeneast · Mar 2, 2015

ORIGINAL: Richard Hamilton

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.

;-) 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.

thirteeneast · Mar 2, 2015

ORIGINAL: kasspa

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

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

kasspa · Mar 2, 2015

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[

]

taylopj · Mar 9, 2015

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

markrwadsworth · Mar 21, 2015

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!

markrwadsworth · Apr 18, 2015

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!!