Intermediate shaft replacement
We've seen quite a few engines where oil appears to be coming past the rear seal of the intermediate shaft that runs the length of the 'M96' engine below the crankshaft. The crankshaft rear main seal (visible in the photo below) can sometimes weep oil, but the lower seal is usually the culprit
There have also been several cases of the Intermediate Shaft (IMS) bearings failing and breaking up inside the engine, causing the engine to fail completely.
There seems to be two separate causes of this.
Firstly, on the initial design of IMS that had a smaller rear bearing and seal, oil can gradually seep past the seal; and secondly, oil can come up the threads of the three bolts which hold the seal cover to the rear of the crankcase (the bolt-holes project right through into the crankcase). The latter can easily be eliminated on re-assembly by the use of the latest mounting bolts that incorporate a micro-encapsulated thread sealant.
The latest intermediate shaft (photo below) introduced in the 2005 997 model runs in a larger rear bearing, plus it also has a wider and more effective oil seal (first fitted in 2001) and this eliminates any leakage problems. But introduced in the 2001, on engines in order to reduce noise, this later shaft also has a toothed wheel to take a similarly toothed drive chain, whereas the earlier type (right of photo) had double chain sprockets, which of course means that this later shaft will also not be compatible with the integral chainwheel on the earlier crankshafts.
As the cost of changing the crankshaft is prohibitive, we modify the later type of intermediate shaft by machining off the toothed gear. We then spline the shaft and fit a custom-made sprocket to suit the original chain drive (on right hand side of photo below). This allows the current improved larger bearing plus the latest oil seal to be fitted.
On engines where a full failure has occured, the only options are either a rebuild or a full replacement engine from Porsche. Full rebuild options and price details can be found here. The quantity of debris that has been drawn through the oil system dictates which components will need to be replaced and if any machine work is required to the crankcase itself.