the RMS problem

I see it mentioned all over, but never really explained. Could someone fill me in in what this apparently common engine problem is, and how it manifests itself? I have a 03 C4S, no problems so far other than a little bit of coolant leak, that was recently fixed by replacing a hose. Thanks!

The RMS (rear main seal) on 996 and 986 cars is very prone to leaking oil. The only thing you will likely notice is some oil on the engine. In extreme cases, you will notice increased oil consumption. The previous design RMS had a spring in the seal with a very high tension level. It sealed very well and had a very low failure rate, although the tension was so great, as the vehicles accrued more mileage there was evidence of scratching/scoring around the crank from the incredibley tight fit. The seal was revised to avoid this damage, but in the process lost some of its tension and has been causing oil leaks for Porsche owners ever since. The best thing to do is be proactive and have that seal replaced anytime the clutch is replaced on the vehicle. If it's not leaking at that time it will leak eventually, and you buy yourself more leak free driving time. There aren't really any documented cases of catastrophic engine failure due to this seal leaking, but it should be monitered regardless. The old adage "it's German, it leaks" seems appropriate.

Phaedrus, do you know why in some cases the engine replacement is necessary? Also, it looks like there is no proven fix for RMS leaks from what I read. I sure hope Porsche comes up with a good solution. Whlie I don't have any problem with my car, it is uncomfortable to know any 996 can have such a problem potentially.

Here's a link from the Renntech board that does a pretty good job of explaining the problem. http://www.renntech.org/forums/index.php?showtopic=15

ubergeek, the quick answer is, that RMS has become so prevalent, that PNCA actually created a tool that checks the tolerance of the seal housing. If it is outside of that tolerance, you get a new engine, since even if they put a new seal on it, it will leak again. If it within tolerance, you just get a new seal. At this point, being that it is the end of the production run of the M96 engine, it is doubtful that Porsche will come up with a definitive fix for the problem. The best we can hope for is that PCNA has a conscience, and will someday own up to the fact that they really should cover RMS replacement for the life of the car.

I still have a question about the RMS. I've read the discussions here and on RennTech but something doesn't add up. Rear seals on engines are nothing new. They have been around forever and to my eye haven't changed much in either thier design or their purpose. While it is true that most seals will probably require replacement at some point, one wouldn�t expect to do so in the first 40k-60k miles of operation on a RMS. It sounds like one of the clues as to what is really wrong is in Porsche's measuring tools. How on earth can the crank shaft become non-concentric with the seal seat bore? That is certainly not the result of a �to tight� sealing spring on the RMS itself. Either the crank shaft itself is bending or the bearings in which it is located are wearing to the point of not maintaining their design specification. In either of those two scenarios, a new RMS will begin to leak very quickly, if not immediately, as it is not intended to be a load bearing element and; Porsche has a very serious problem with its engine design. It would be nice to know what the truth is and what to do if you don't currently have a RMS problem. Should the oil be changed more frequently? Should the RPMs be held below 6500 or some other number? Would installing additional cooling, as in a third radiator, help? And, lastly, is there a plan to deal with this after the warranty period is exceeded? Hank

I am sure this has been discussed many times but I am really wondering why porsche owners w/RMS issue aren't taking this issue to PNCA to the next level. I guess most people are covered under warranty so far but by next year there will be many 996s out of warranty. It will be interesting to see how this issue gets magnified once people find out they will have to pay for a replacement engine...(I hope the number will be very small)