Kolbjorn S

There's an interesting note in the April edition of Excellence, regarding RMS leaks on Boxsters. This is attributed to that the tail of the crankshaft suffers from lack of support. Instead of resting on a bearing at the tail, the crankshaft is fitted with a chain-drive connected to the intermediate shaft.
This problem is thought to be enhanced on manual-gear cars, where the end of the crankshaft also bears the weight of the flywheel and clutch assembly. It is then the motion of the unsupported crankshaft tail that causes wear on the rear main seal.
Wonder if this could play a role on the GT3's as well, and would the crankshaft on the turbo have better rear support?

stules

If crancase pressure is the culprit, then possible the crankcase breather mod
https://rennlist.com/forums/showthre...kcase+breather
may be of benefit.
Anyone having done the mod may be able to chime in as to whether they had RMS issues afterwards. Just a random thought.

Kolbjorn S

Is this correct? According to the tread, this mod actually raises crankcase pressure, thus causing greater risk for RMS leaks?

f4 plt

Everyone with this problem might want to ask your service guy to let you see a seal. the older seals on the 996 had rubber (ridged) around the outsde the full width of the seal. The new seals have a narrow teflon band that covers only 1/2 the width of the seal and the other half is a metal ring Interesting as they have reduced the sealing surface area with the new seals. So far I have 150 miles of hot South Texas highway driving on my new seal and it is holding. Of course this is my third seal.

Mussl Kar

Cha Ching! My RS is in for it's second RMS. I kept getting temp sensor fail lights so I brought it in. I pointed out that there is still an oil leak coming from the top of the motor somewhere near the hose that connects to the tank, got that info from the tuner who did my R&P. Sure hope to get it back Friday.
Upside is that I get to play with a Caymen juice drive for a few days longer. Big whoop!

Chilipadi

Just dropped off an 08' GT3 with 600+ miles for an RMS leak as well.

sjgreco

Read below, it may be the reason the GT3's and RS's have RMS problems.

I had never heard of this problem with the GT3s before. I had figured same old crankcase, same old seal, what can go wrong, they never leaked before. Since hearing from you I have looked into this and find that they have used a different rear main seal than the “Turbo” even though they use the same crankcase. A GT3 seal (only GT3 not Turbo) appears to be installed "backwards" when you remove the flywheel. When you remove the seal you will find holes in the engine crankcase at the 9 and 3 o'clock positions (only GT3 not Turbo). These holes allow crankcase vaccuum to draw the lip of the seal tight against the crankshaft. (Again visualize the seal as being bacwards and the angle and face of the lip facing outwards instead of inward as would be normal.)

So, what we have are a few conditions that may not be favorable: The seal is really only very tight when the engine is running and there is good vaccuum. There is no check valve between the oil tank and the engine like the turbo has, so the only thing stopping the flow of oil back into the crankcase from the tank is the clearance between the gears in the oil pump.

Especially when they sit for extended periods of time, these cars may develop a slight seepage since the seal is not completely tight, and the oil level rises above the level of the two "ventilation" holes and accumulates in the compartment behind the seal (between it and the engine block).

Since a lot of owners don't drive these cars very much, (a lot of GT3RS cars especially), Porsche advises customers that under these conditions (sits for weeks without running), some seepage is normal.

Back when we had the "first" GT3 (996) - and this was actually the 2nd generation (Europe had a version with a different engine 1st, (ours was the 996GT3 F/L-facelift), there was a change to the seal. Porsche had more trouble with incorrectly installed seals than anything at that time - the Porsche techs saw a little seepage, thought the original seal was in backwards, and proceeded to install a new seal incorrectly (really backwards) that leaked even worse!

All this being said there was one change to the seal back a few years ago, and all the seals have been the same since. Porsche just released some new information in the spring about a "spacer ring" that fits between the seal and the crankcase and spaces the seal out to ensure a good compartment for the vaccum to build up behind and pull the lip tight. The seal itself hasn't changed.

All this being said, by nature of the design, and the laws of physics and huydraulics, some slight seepage under certain circumstances will happen.

It is normal to have light to heavy engine oil sweating (very light leaking) at the rear main seal (RMS) area of the GT3's, R's, RS's & RSR's because these cars utilize a very special double lip RM seal. This rear main seal is basically installed in the engine crankcase backwards and it allows the crankcase to breath giving the engine a small horsepower increase during higher RPM's and substantial load ranges.

Mussl Kar

Good read. My RS only sits for the winter months though. It gets run hard at autox at least once a week during the season and I load the car up in the AM, drive to the autox and run, and come home and unload. Found oil on the trailer after unloading the car. My leak is about two months old at this point and getting worse. Porsche mechanic said I was in danger of contaminating the clutch.
Before the first one was replaced I would find a silver dollar size puddle whenever I parked it, puddle would not get bigger either. Latest puddle is 3 times bigger.

f4 plt

Good comments and almost exactly what I was told by a Porsche NA Field Technical Manager.

I have drawn the conclusion that Porsche really does not have a solution to the RMS issue. An earlier post stated that there is only one new GT3 (GT3RS) engine in Porsche's inventory. This may not be exactly true but I would imagine that there are only a small number. With such a small inventory and such a significant number of vehicles with repeated seal leaks a solution becomes a real issue. So far my third seal installed only 200 miles ago is holding. Mine should be a good test with the heat we have in south Texas and the distances I drive the GT3.

That said I am off to the dealer today as they want to do more tests to explain the high oil pressure I have. AS I posted on another thread my pressure gauge pegs at 5 bars (top of the gauge once the engine exceeds 2000 RPM and stays there. The owners manual on page 85 states that at normal operating temps. the oil pressure should indicate aprox. 3.5 bars at 3000 RPM. The factory shop manual states that at normal operating temp at 5000 RPM the gauge should read 3.5 bars or slightly higher. So far Porsche NA is silent on why my GT3 indicates so high and outside the limits of either manual. Aside from those two issues what a great vehicle. I could not close without stating how pleased I am with my dealer. The service department has done more than normally expected to make my car right. they are professionals that really believe in "Customer Service"

flash1034

My oil pressure guage also pegs at speeds. Hmmmm.. I didnt realize that was a potential problem...

Flash

zellamsee

The comments from sjgreco are consistent with what I heard directly from the head of Porsche Motorsport in Germany a few months ago -- that is, if the 997 GT3/GT3RS is not driven frequently, some minor leakage can be expected @ the RMS. He explained to me that the engine needs to come up to normal operating temps with some regularity in order for the leak to stop. Hence, he said "drive the car more!" If the RMS leak is in fact "normal", though, why would Porsche agree to multiple "fixes" under warranty? Seems like a big waste for all involved . . . .

sjgreco

I agree totally with your assessment, here are some additional comments on the subject in response to one of my emails.

Bruce thank you for the informative response. So I guess most of the GT3's and RS's will likely develop some sort of RMS leak. I was told by the guys at my dealer that infrequent use was the cause for my 996 GT3 RMS leak. Is this a design flaw or something that Porsche has decided is immaterial relative to the performance of the GT3's and RS's. Is their position a little oil leak a small trade off for having race car performance. I think it would be a great topic for your magazine, at the very least provide a plausable reason for so many leaks. Based on what I have read on posts, it seems Porsche is making a sincere effort to find a real fix. Must be costing them a bundle for warranty repairs relative to many/mutiple RMS leaks or lemon law problems.



I am going to publish the same answer I sent to you, so it will be interesting to see the raction from the readers. Sounds to me like Porsche doesn't think that it is really a problem. If they go faster they won and this is a very specialized car.

mooty

i dont know why my does what it does and how to solve RMS, but i am adding another confusing data point here.

my cars has pretty high mileage RS at 18000 miles. it had RMS leak at 1000 miles, 12 months or more ago. it was fixed then bone dry.

i often park the car untouched, no batt. maintainer at all for 4-6 weeks. sometimes i would only drive it 5 miles to get milk when others cars are blocked in. but when i do take it out to drive or track, it will see about 1000 miles in a 3 days. so, leaving the car sitting for weeks on end doesn't seem to produce RMS leak, at least not on my car.

i was told by a porsche master mechanic that there's a "seal" and a very veyr thin "ring" when they replace RMS, the replace both. in fact the latest bulletin (i dont have a date of the bulletin sorry) states that both the seal and the thin ring should be replaced. i dont know if that would solve your problem.

todinlaw

Once I got over the idea that my $120,000. car had an oil leak in it, its not that big of a deal. my car only leaves a small drop about twice a month. the harder I drive it the less it leaks. getting some more HP for a drop or two of oil is not a big deal. I am totally comfortable with it. My only concern which may never materialize is if I will be punished at some point down the road in terms of resale value, then I might me upset.

f4 plt

I was at my dealers today when they attached a calibrated oil pressure gauge to the car and took readings at various RPM's up to 5000RPM The results are interesting. First and foremost my OEM gauge mounted in the gauge cluster is accurate. That said here is the disturbing information. At 3000 RPM the in dash gauge was pegged and the calibrated gauge read 6 bars ( a full one bar above what the in dash gauge is capable of reading. Remember the Owner's manual on page 85 clearly states that at 3000 RPM the gauge should read aprox. 3.5 bar so thus the actual oil pressure is almost twice what the manual states and unreadable on the in-dash gauge. Second at 5000 RPM my car registered 7.5bar on the calibrated gauge. On Porsche on-line technical sight the Service Manager should me that it should register 7 bars .... still far above what the in dash gauge reads. Bottom line the in-dash gauge is worthless, and the tech data oil pressure at normal cruise is well above what the gauge can read so it will always be pegged (Yes I know RPM at 70 MPH is aprox 2800 RPM) My car is still at the dealer as until Porsche puts something in writing that the data in the owner's manual is incorrect and it is normal to have the gauge pegged during normal operation I will not drive it to preserve my warranty ... already on the third RMS seal so the warranty is important. I'm sure the response from Porsche will interesting. At a minimum all gauges should be changed out to allow owners to see the correct oil pressure...... don't think that will happen. More to come