How common is IMS failure REALLY?

[Lil bastard]

Originally Posted by Brucelee

Why do you say this?

Probably refering to the redesign of the Intermediate Shaft for the 2001 MY.

In 2001, Porsche switched to a shaft with a single toothed sprocket and eliminated one of the bearings in the process, ostensibly to address issues with noise and vibration. It is thought that the elimination of this bearing introduced some flex to the shaft not previously observed. This allows the cam chain to sometimes slip and interupts the mechanical timing (not desireable - especially on an 'interference' engine).

The smaller rear seal on the original shaft allowed oil to leak more easily, so a larger seal was incorporated with the redesign. Also, the way the shaft is produced, oil is allowed to reach the threads of the seal cover bolts allowing oil to seep past them. This was corrected by the introduction of bolts pre-coated with thread sealant which seals the threads on installation.

As a result, IMS failures are almost exclusively reserved to the 2001 model and newer. It is very rare on an earlier car.

Autofarm UK makes a fix which replaces the single toothed sprocket with the original double sprocket while retaining the improved shaft, bearing and seal.