Please welcome me to the RMS Club + a story

The other night, I saw a bit of oily residue under the car, so I figured I'd take it to the dealer. Turns out that the RMS was just beginning to leak. So I say to the service manager... "guess it was only a matter iof time, huh." And he says... "you must be reading those internet sites." I get the verdict later today...hopefully just a new seal will be required. And for those keeping track, the car is a 2002 C4S with 21K miles.

ya the service managers hate the "internet", i guess they like to think all porsche owners shouldn't know anything about their car other than what they tell them

WELCOME!!! The internet is a great amplifier, but despite all the RMS chatter, we still don't know (1) the actual failure rate (2) what Porsche feels is an acceptable rate and (3) if the new part reduces the failure rate to near-zero. In absense of these facts, it is easy for emotions to shape our perceptions. You'd think Porsche management would step up to control the situation that is effecting the perception of their cars (with the facts, as a starter).

redcab, maybe they're not stepping up because 1) there's no solution for the problem because it's inherent in the engine blocks and 2) they don't want to admit their engineers made such a major mistake! i wish i could get a figure on the actual failure rate though...

Here is some info I posted in June after our local Porsche group came back from a tech session at our local dealer. http://www.renntech.org/forums/index...&st=0&#entry24 The new tool that seats the seal a bit deeper had just come out in April. I can think of 2 local owners owners who had the seal replace with the new tool and they still had leaks. The problem was not solve as to their cars. Also people talk about a new style seal like it just came out. The new seal went into production in February 2000. This is the same seal they still use but with the new tool it is seated a bit deeper. Jeff

Looks like mine is starting to leak (27K miles). Is this a problem for boxsters as well? Has anyone really ever figured out why this occurs? Btw, I have an extended warranty which covers the replacement. Looks like that was a good idea, though I think the manufacturer should extend the warranty coverage for a design problem!

Update: New seal, tolerances okay, and ready for pick-up...let's see how it holds. I've learned that if I keep this car past 50K miles, I will definately be getting an extended warranty! And thank you toolpants for the excellent link.

Same issue with the Boxster as we share the same basic crankcase with the 996. The 2 local cars I mentioned were Boxsters. A third local Boxster friend last year also had a seal which leaked, was replaced, and leaked again. I did not include him with the other 2 since I do not know if his first replacement was done with the new tool. One of the 2 Boxster owners I mentioned had multiple seal replacements - new style seal and new tool - and it still leaked. They replaced her motor and the replacement leaked. Porsche then bought back her car and she now has a new 996. At 8,000 miles her 996 leaked. Porsche has never published anything as to what is the nature of the problem. The simply put out a TSB to the dealers that says a new seal design has come out and it should be used if the seal needs to be replaced, and that the old seal has been discontinued. Porsche does not even acknowledge there was an issue with the old design. Same thing with the TSB that came out last year for the new tool to install the seal. The TSB says to destroy the old TSB with the instructions on how to use the old tool, and to use the new tool. They do not tell you it is their attempt to fix leaks or what is the nature of the problem. I feel sorry for the mechanics. If a customer wants to know why the engine leaks what can they tell the customer since their is nothing official from Porsche. But any mechanic experienced with the M96 motor can give you an educated guess. The factory mechanic who puts on our tech sessions is a Boxster owner and a PCA tech advisor. He told me what he though it might be. An local independent Porsche shop also put on tech sessions and one of the mechanics told me what he thought it might be. And both of their educated guesses were the same.

I read the info in your link (thanks!). It describes repair issues, but I don't recall seeing what is the root cause. So what was the speculation? Thanks again.

Mark, Sucks that it happened, but sounds like it took them no time at all to fix it. At least now you can go skiing this weekend

Yes sir! I was afraid I'd have to stuff the skis inside the loaner Camry

The root cause was described to me as follows: During the crankcase machining process the "bits" were not replaced at a high enough frequency. This resulted in the bore becoming overheated and non-cyclindrical. So, the first X number of case's produced were OK while the subsequent cases started getting worse. Seems to make sense based upon the variablility in the severity of the leak (new engine/multiple seals/single seal). Just what I heard.

I know you repeating what someone told you. Makes no sense. This is a machine, a motor, an internal combustion engine that has been around for a 100 years or so, not including steam engines. Not an electrical part or a computer. An oil seal has a simple job to do - hold in motor oil. Have no idea what "bits" are unless it is the tool for the cylinders. And if that is what a bit is then I will show you picture of Porsche's little cost saving trick they did in 1998-99 and why you now have a 4 year warranty. Jeff

Jeff, Like I said it is what a Porsche mechanic described to me. The "bit" refers to the tool which was used to bore out the case. The analogy he used was that you can't seal an egg shaped hole with a round seal. If someone can enlighten me as to the cause I would love to hear it.

When I get my computer back from being fixed I will put up an exploded (sorry for the pun) view of the M96 motor on renntech and try as best as I can to explain what the 2 mechanics told me at the tech sessions. Now if you want to see Porsche's little secret they did with the Boxster motor in the early days....... http://stau.jowood.de/phpBB2/viewtopic.php?t=1416 Some 1998 Boxster owners experienced engine failures and back in 1997-1998 there was only a 2 year warranty and Porsche was getting a bad rep. 1999 was the year the 4 year warranty started. Jeff

Tool Pants, For what it is worth, I was told that the crankshaft in the M96 motors "wobbles" at the end, or can wobble and that the only way to fix this problem is to mount another set of bearings at the end of the crank to keep it from wobbling. (expensive and custom operation) The consistent wobble over time wears out the seal. Seems like read something in Pano or Excellence about this awhile back too...

That is very, very close. Remember, there is a seal at each end of the crankshaft, and which one is the problem? The rear. which also has a lot of weight bolted to it. Such as the flywheel, clutch disc, and pressure plate. The M96 motor uses a bearing block to support the crankshaft - something Porsche had never used in the past. Something is moving. I do not get Pano and do not remember seeing it in Excellence. Would like to see the article if you can find it.

If this is the case, does it mean that the replacement seal is likely to wear out over time as well?

I would say yes, unless through removal and reinstallation you happen to get the parts back together in a better alignment that doesn't cause as much wobble and doesn't put as much pressure on the rear seal. Tool Pants - the article wasn't about seal leaks per se, the article was discussing issues with the engine and one of them that they said was known to cause problems was that the crank shaft wobbled so in order to fix that problem they installed another set up support bearings. I'm pretty sure it was in Excellence, let me see if I can find it.

Ah here it is, October 2003 Excellence pg 119: (this is about the modifications Stola has done to their engines) "The crankshaft is checked for dynamic balance before being subjected to an additional chrome-moly hardening process. Gemballa says that the crankshafts in wet-sump sixes have been known to wobble in their bearings under high loads, so the end of the crankshaft is modified to take an extra bearing that rests in a custom housing OUTSIDE of the block." What isn't clear is what constitutes a "high load" and whether or not the problem plagues every day engines, but if the problem truly is the crank support then this would explain why some cars continue to have repeated seal failures despite new seal designs and despite some new tool to seat the seal deeper, etc. The only way to really know would be to dynamically check the crank for a wobble while it was still in the car and I'm not sure how you would do that. How far out of balance does it have to be to create the wobble and cause a leak? Does simply dropping the tranny and moving the clutch assembly around, etc. create enough "rebalancing" effort that when you put it back together you have less or no wobble and then the seal holds? Does this affect both manual and automatic transmission cars? (In other words does one balance the wobble better than the other?) What I think Porsche should do, and what RMS owners should demand, is a letter from Porsche they they will continue to fix RMS leaks in their car until they no longer own it, so if 20 years from now you still own your car and you get RMS you are still covered. I mean Porsche engineers aren't stupid, I'm sure they know for certain what the problem is by now. If the problem is still occurring it means that there isn't some easy solution to fix it like a new seal but rather an engineering change that for financial reasons the risk - reward calculations came up that it was better for them to fix the cars on a case by case basis that had a problem than to put $$ into a redesign effort at this time. They'll probably wait for the next engine redesign, maybe the M97?, and address the problem then. Some bean counter probably said the impact from disgruntled RMS victims would not impact sales of new Porsches enough to warrant the expense of fixing the root of the problem. Here on Internet forums we have a skewed view of what the rest of the world experiences with their cars. Joe average Porsche owner sees a spot of oil, takes it in and the dealership tells him its a seal, covered under warranty, fixes it up and sends him on his way and he has no clue how often this is really happening or why and probably doesn't care. From a purely physics point of view I am surprised that a flat-6 engine wobbles the crank more than say a V-6 where the loads are concentrated in a smaller diameter range of the crank rotation. Then again, as the article says it may simply relate to the support structure of the crank. It would be interesting to see the difference in the crankshaft support structure for the M96 engines vs. the prior generation. Maybe PorschePHD or someone else has some shots like that?

I read on here that the problem is not out of round but out of concentric which is why there is a go, no-go gauge to see if the seal flange is within tolerance of 3 thou. (Id' like better than 3 thou on my precision built motor). You would have to assume that it left the factory concentric but that it drifted over heat cycling and torque load which is probably due to P trying to make the lightest engine case possible. If the case is distorted there is no practical fix that I could imagine. P does the right thing by replacing the problem motors. Hats off to them, we design high stress components to the very best of our ability and we think they're brilliant but they are not always perfect. The CNC machine tool story sounds a little weak, I imagine P has the latest self measuring tooling, besides QC would pick that up, the fitter would reject it, etc. etc.

Webtool - I believe the tolerance is .03 mm ~= 0.00118 inches. Yes by now I am sure Porsche knows exactly what the problem is. If in fact this is a design flaw then they are taking a big risk. On the other hand it seems pretty difficult to believe that they could make such an "obvious" error in terms of calculating crank loading, bearing wear, case distortion, etc. So maybe this is a borderline case where they tried to save a little too much weight or cost or the quality or materials control in the manufacturing process is not what it could be.