Stephen Tinker

Doc - the IMS bearing is only splashed with oil by default - its lubrication was only meant to be by the pre installed grease, not oil fed.
But as the "seal" is not really a seal but a plastic shield the oil slowly entered the bearing.

The theory is that Porsche extended its oil change intervals which, coupled with short trips and long periods of inactivity caused the acidic byproducts of combustion to build up in the oil. These acids tend to attack the bearing surfaces after the original grease had been flushed out, causing brinnelling and pitting of the steel ***** and race, eventually causing the bearing to fail.

The hollow shaft that connects the two sets of timing chains eventually fills with this oil/acid mix (no drainage facility), so the ball bearing literally sits in this corrosive enviroment. Quite a few people have noticed when replacing the IMS assembly that once the bearing was removed quite a lot of this putrid oil drains out of the shaft.

That's the theory anyway..........

docmirror

Becoming more clear, thanks Stephen.