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Hi,
C'mon guys, a little common sense here please. Why can't people accept that RMS failure is inherent on the M96 engine? It's nothing you do, or fail to do. Stop trying to let Porsche off the hook for such poor engineering, I mean even Kia got this one right!
Shaft Seals have been around far longer than the Automobile (think Locomotives, Steam Engines and Industrial Machinery). It's very straightforward stuff. I've owned 2 cars whose Main Crank Seal was just a piece of Rope! And, if they were installed correctly, they didn't leak, even the slightest, for well beyond 30k mi.
Theoretically, the crankshaft should not move, therefore a butyl rubber seal seated against the shaft should provide a seal adequate for the 45-55PSI of Oil Pressure. But, this presumes that the Seal and the Shaft are center-aligned.
OK, so it's not a perfect world and the Crank does have some float, but the book says this axial play should measure 0.05 to 0.24 mm, that's an incredibly small degree of movement, well within the deflection capability of a Butyl Rubber Seal.
So, it isn't the Crankshaft's fault. But, if the Seal is installed off-center (as when the Bore opening in the Block is cast that way), it can reach it's limit to flex and still maintain sufficient pressure around the Crankshaft to seal. And this is why there is premature RMS failure on the M96 engine.
Now, there is direct contact between the Rubber Seal and the Crankshaft, so eventually even a small amount of friction, multiplied by hours of use will result in the Seal failing, in that way, it is a sacrificial part. But, most Automotive Crank Seals go 100k mi. and beyond before this occurs and the Seal fails normally.
Porsche should get in front of this and not only admit the issue, but solve it, remember, they are producing the same piece of hardware today, essentially unchanged since it first was produced 11 years ago now. For a Company with the history, prestige and price point that Porsche has, it's just a disgrace. Compounded maybe by the fact that now they're pointing the finger at the driver and crying Operator Error...
Happy Motoring... Jim'99
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