Panorama magazine has an excellent technical section where the real main seal issue is discussed frequently. The question and answer sessions are also available to everyone on the Porsche Club of America website. Here is a sample response to a reader's RMS question:

Quote:
The issue is as follows. The crankshaft is sealed by the RMS. The crankshaft rides in a cradle inside the crankcase. Some engines not representative of the class, but specifically defective, had a cradle that was misaligned relative to the case. Therefore the crankshaft rode off-center in the bore which was to be sealed by the RMS. One could argue that the hole was off-center; the result was the same, it would never seal unless corrected. Correction requires a total engine rebuild and/or at Porsche's discretion they could elect to replace such engines at their expense with new or factory remanufactured units.


Joel Reiser - PCA WebSite - 3/13/2004