IMS stands for ‘Intermediate Shaft Bearing’, which is the supporting bearing of the intermediate shaft, on the flywheel end of the motor (See red arrow below). The purpose of the intermediate shaft is to drive the camshafts indirectly off the crankshaft. By using an intermediate shaft, the speeds of the chains are reduced, which is better for the chain life.
What Porsche models are prone to IMS failure and should be replaced?
- All 986 Boxster models
- 987 Cayman & Boxster models up to engine number 61504715
- All 996 models (not including GT and Turbo models)
- 997 3.6ltr with M96/05 up to engine number 6950745
In worst-case scenarios, the cam timing can also be thrown off, which causes valve to piston contact. That is considered a catastrophic failure which would require a complete engine replacement.
One thing is for sure; once you have experienced an IMS bearing failure, there is NO turning back. A complete engine disassembly is required to replace the intermediate shaft and in most cases, complete rebuild or engine replacement is your ONLY option.
We’ve been managing the maintenance and serviceability of IMS bearings for quite some time, over the many years we’ve tested a few different solutions and after it all, it’s the LN Engineering IMS Retrofit that is the one for us. By converting the single row of ball bearings to a dual row setup, the Retrofit allows for 90% more load capacity. It is clear to see that the reduced load capacity of the single row IMS bearing is a significant factor to the increased number of failures. That’s why the installation of a dual row ball bearing is the logical evolution for the IMS Retrofit.