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Hi guys, I did a lot of research on this forum (a great resource btw) before I recently purchased a used C4S tiptronic. While I never planned on purchasing a tiptronic 911, once I weighed up the chances of getting a manual which may have worn syncro's and the fact that quite a lot of people seem to suggest that there is a lower IMS failure rate on a tiptronic cars I decided to go for a tiptronic car.

Not disappointed at all, the performance is great and I am really pleased with my purchase.

This weekend the car was up on a ramp so I took the opportunity to take a look underneath and I noticed that there appears to be some oil visible where the engine meets the gearbox. Dare it be the RMS and should I be panicking?

I have attached some pictures for people’s opinions. I am not going to panic, the car hasn't lost much oil and doesn't appear to be leaking on the ground

Look forward to your opinions. Thx

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post-874-0-74744500-1331127229_thumb.jpg

post-874-0-28945600-1331127285_thumb.jpg

post-874-0-50221200-1331127296_thumb.jpg

Edited by Porca911
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Hello!

Yes to me that looks like you could have a leak from the bell housing. The second, third, and fourth pictures are pretty revealing.

Either from the RMS seal or the IMS seal, or both!

I wouldn't panic though, certainly it should be addressed, but chances are the car has been like this for a long while. Does the car use a lot of oil?

You can clean the area and see more precisely where it comes from, or remove the transmission and inspect/repair those seals.

Hope this helps.

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Hi, well I haven't been checking using the dipstick. But the dash display always shows the oil as full. Although I am not sure how accurate that is? I will clean it up and monitor how it goes. Out of interest can those seals be replaced by only removing the gearbox or does the engine need too come out too? Thx

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I would make sure the dipstick matches up, but if it isn't loosing a ton of oil chances are it has been leaking for a very long time.

Yes you can drop the gear box only to replace the RMS and IMS seals, engine can stay in the car.

Typically, when the box is dropped, a lot of people like to also replace the AOS ($100USD) and IMS bearing ($600USD) as preventative maintenance.

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Okay been watching some YouTube vids on RMS and it appears to be quite common. The high cost is mainly due to the labour involved as opposed to the cost of the parts. So I will change the oil, open up and check the oil filter for any metal deposits which will indicate a possible issue with the IMS bearing and I will get hold of a magnetic sump plug and change oil every 3-6 months.

In the mean time I will start my research to find a experience and reasonably priced specialist who can change the RMS for me and while I am at it I will get the IMS bearing replaced with the LM Engineering upgraded bearing as it certainly appears to be a no brainer!

While I didn't plan on spending this extra money, as I plan to keep hold of the car for a long time I think it's probably best and will reduce the voice in the back of my mind which keeps on reminding me that a failed IMS bearing will mean a failed engine. So the best part of 2k spent isn't the end of the world really is it.

Out of interest (and I think I know what the reply will be to this one) someone suggested that there is an additive which you can add to the oil which is supposed to seal any oil leaks. I know, I know, screams DONT DO IT but I thought I would ask. Is this a sane option?

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Additives to stop an engine oil leak are a band-aid, at best, and they may give you a false sense of security. There is no way to definitively know whether it's the RMS or the IMS that is causing the leak, short of dropping the transmission to have a look.

+1 on cleaning the area and monitoring it to see how severe the leak is. Since it's not dropping any oil onto the ground, it doesn't sound like a serious leak, assuming that it's coming from the RMS.

Regards, Maurice.

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There have been many, many discussions on replacing the IMS bearing on this forum including an in-depth discussion with Casper labs recently.

LN Engineering has the most mileage on their replacement bearing although there are a few other new options including one from Casper. FWIW I have booked my 02 996 into the shop for the LN bearing replacement on Monday even though nothing is noticeably wrong.

If you are already replacing the RMS and have the transmission out it probably makes sense to replace the bearing at the same time.

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Hi fpb111 - Yes Autofarm are currently top of my list of companies not too far away from me with the experience and reputation to do it but I will be contacting other reputable specialists for their prices. They advertise the prices for the IMS retrofit, but I need to speak with them regarding what changing the RMS at the same time add's to the equaltion.

kgoertz - my cars the same age as yours so I now feel when I am getting the RMS done I will also get the LN bearing done. It's just best for peace of mind.

Out of interest whats the going rate to get this done in the States? Seems to me to cost almost $3k to get the bearing alone changed on a C4 cars in the UK

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$2500 USD seems to be an average price for IMS retrofit along with RMS seal, and sometimes including a new clutch kit and AOS.

The RMS itself is about $15 USD, and the time it takes to do is miniscule compared to the rest of the job, especially for a shop who already has the correct tool.

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I'm not quite sure on the price, but I think it is something like 8 hours work. Adding in the price of the bearing (not sure but somewhere around $6-$700 USD) that should come to the $1500-$2K. Add in a clutch kit for $500 and you close to $2500 US as logray mentioned. Although that is for the C2 manual. My understanding is that it is more for the TIP and possibly more for a C4.

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I had a similar situation whereas I just purchased (December '11) an '01 996 Cabrio. I went ahead and did the IMS upgrade and clutch while we were there. I Love my new car and feel good to have the upgrade since I plan to keep the car long term.

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I have been speaking with a few specialists today and they tell me the reason the price is more for the C4 is that the whole engine needs to come out. Can't remove the gearbox while the engine is still in as you can on the C2's. So it's more time consuming job.

I was surprised that one specialist said that they don't do the retro fit. They would change the seals (on the IMS and the RMS) but if the IMS bearing had play in it then they would tell you that you have had it or I suppose recommend an engine rebuild!! Yikes!

Another told me that a lot of RMS leak and that Porsche had changed the design of them on a number of occassions to try and resolve it. I was advised that if it's not leaking much then to try and live with it.

Also during the discussion it was mentioned that if the leak is from the IMS the that is the seal in the triangle cap which bolts onto the engine. What I am not clear about is if the oil is leaking from the IMS does that mean the seal on the bearing had failed and the lifetime greese was probably getting washed away which then means expect excessive wear??

Any ideas?

And finally one specialst suggested that the bolt on the IMS bearing can snap, I was under the impression that the failures happen because the bearings lose there greese and the bearing wear's excessivly and can break appart. I never knew that the bolt comming off of it can also break...

As my car is a tipronic I have no clutch to change. I do feel if I did at least that would help to justify the job a little as you need to change that eventually.

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I was surprised that one specialist said that they don't do the retro fit. They would change the seals (on the IMS and the RMS) but if the IMS bearing had play in it then they would tell you that you have had it or I suppose recommend an engine rebuild!! Yikes!

If the bearing has play in it, you can retrofit and there wouldn't be a reason to rebuild the engine unless it wasn't running when the retrofit is to be performed (because of a failed bearing). That is a very good thing if you can catch an engine with a failing bearing before it actually fails. It is very well documented that many cars have been saved tremendous expense in this manner. In otherwords, no reason to rebuild the engine, rather just retrofit the bearing and the car is "good as new".

Another told me that a lot of RMS leak and that Porsche had changed the design of them on a number of occassions to try and resolve it. I was advised that if it's not leaking much then to try and live with it.

Yes the design has changed multiple times. The latest design 2004/2005 IIRC is great, no leaks. But yes I would tend to agree that if the leak is not severe it is not too bad a problem to live with. Then there are cases that will chronically leak regardless of the RMS, but there are probaly very few of those still around.

Also during the discussion it was mentioned that if the leak is from the IMS the that is the seal in the triangle cap which bolts onto the engine. What I am not clear about is if the oil is leaking from the IMS does that mean the seal on the bearing had failed and the lifetime greese was probably getting washed away which then means expect excessive wear??

The IMS flange seal (triangle cap) is different from the IMS bearnig seal. The IMS flange seal prevents oil leaking out from the engine case into the bell housing (as can the RMS which is direclty above it). That seal has been updated from early year cars. The stock IMS bearing seal is inside the engine, Porsche has not updated this design, the only thing they've done is mess around with the size and strength of the bearing. The lack of lube inside the IMS bearing because it is sealed is a totally separate issue from the IMS flange seal allowing oil to leak outside of the engine.

And finally one specialst suggested that the bolt on the IMS bearing can snap, I was under the impression that the failures happen because the bearings lose there greese and the bearing wear's excessivly and can break appart. I never knew that the bolt comming off of it can also break.

There have been documented cases of the center beraing support going poof, which is one of the reasons why you might want to consider retrofitting the bearing (which includes a stronger center bearing support).

As my car is a tipronic I have no clutch to change. I do feel if I did at least that would help to justify the job a little as you need to change that eventually.

All the more reason to drop the engine with trans, especially if you have a tip C4... dropping the engine is not hugly complex, but it might double the labor over a simple C2 manual where you can just drop the transmission to do the work.

GL

Edited by logray
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  • 4 weeks later...

Some really good, informed discussion here. It is important to note that the updated IMS bearing supports with the wider 3 rib seals also have very significant seal MATERIAL change. The early black o-ring seals are made of buna rubber. The 3 rib are orange (silicone). If you are using synthetic oil(which everybody should if they can afford it), the buna will eventually soften to the point where it will not seal. On conventional oil, silicone rings of similar size will take a compressive set in less time than buna, but life expectancy under synthetic oil is still worth making the material change. Metric silicone o-rings can be had from specialty houses if you wish to put them on the original support.

Always check the bore of the IMS for a really smooth varnish and burr free surface. You can damage the o-ring on the stud if it is not smooth and lubricated when it is assembled.

The Porsche service manual torque for the IMS stud nut is 10 ft/lbs. Many of the failures you hear about regarding these studs are the result of damage beacuse of over torque. All this stud is designed to do is set the running position of the IMS. It takes no axial load in service beyond the stretch imposed by tightening. It is also free of any radial load whatsoever (radial loads go thru the part of the support in the bearing ID.

BR

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