We get asked this a LOT, which there is a lot of scaremongers on th entered talking about IMS bearing failure in fact there are very small numbers of failure in the real world. If you are on the look out of r a 986 996 and are worried about IMS bearing failure, ask to see service history showing regular oil changes, I lot of owners now are changing the IMS Bearing as preventative maintenance. It works out around £1200 to have this done by us, I think that is a fairly small price compared to an engine rebuild / replacement.
What on earth is the IMS bearing?
IMS stands for ‘Intermediate Shaft’, and the IMS bearing supports the intermediate shaft, on the flywheel end of the engine. The purpose of the intermediate shaft is to drive the camshafts indirectly off the crankshaft. Its a steel shaft that runs through the centre of the engine. On one end of the shaft is a sprocket from which the cam chains are driven. On the other end is a pulley that drives ancillary equipment. The end of the IMS that drives the cam chains, sits inside a housing that locates the IMS shaft and supports it. The housing spins on bearings for smoothness, which is where the problems arise. These bearings self-lube. Given the role of the IMS sprocket in relation to the camshaft timing, the result of a failure is fairly obvious. When they overheat, the bearings start to disintegrate and the metal swarf finds its way into the engine causing damage. If pathways become blocked by debris it can cause significant engine damage. In some cases, the IMS bearing race collapses altogether causing catastrophic damage to the engine. Neither option is desirable. Porsche models which ran with the M96 and M97 engines were 911’s, Boxsters and Caymans built between 1998 and 2007 model years.
Which Porsche models are prone to IMS bearing failure and would benefit from an IMS bearing upgrade.
- All 986 Boxster models post 98
- 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
What actually goes wrong?
There are so many reasons for bearing failure, and usually each failure is due to a combination of causes, not just a single cause. The IMS bearing failures are caused by the lubricant in the IMS bearing housing leaking out or drying up and then the bearings overheating (well, they are 20 years old!). When they overheat, the bearings start to disintegrate and the metal debris finds its way into the engine causing damage.
What is the worst case?
In most scenarios, the cam timing can also be thrown off, causing valve to piston contact. In that case, the engine will need a full strip down and rebuild.
Once you have the dreaded IMS bearing failure, there is NO turning back, you have to try and catch it early.Its likely a complete engine rebuild is needed to replace the intermediate shaft and in most cases, complete rebuild or engine replacement is it. Ouch
What can be done to fix this common problem?
There are new easy to install IMS Bearing kits available. https://wooliesworkshop.com/products/porsche-911-boxster-986-996-997-intermediate-shaft-ims-bearing-upgrade-eternal-fix-ims they can be fitted by us, another specialist or at home by a competent home mechanic.
Are there any early warning signs?
Nothing easy to spot but regular oil changes and checking for debris in the filter will give you an idea.