When should an IMS bearing be changed?
Just over 388,000 Porsche 911 models were produced between 1998 and 2012, covering the 996 and 997 model ranges. The 996 and first generation of 997 shared a similar flat-six naturally aspirated engine (engine codes M96.01-M96.05 and M97.01). It is a glorious sounding engine with great power and torque characteristics but it is not without issues. Probably the most widely understood issue relates to the Intermediate Shaft (IMS) Bearing. Before we get into the IMS bearing replacement options, it is important to fully understand the role and operation of the IMS bearing.
The intermediate shaft is 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-lubricate to keep temperatures down and ensure smooth operation. Given the role of the IMS sprocket in relation to the camshaft timing, the consequences of a failure are fairly self-explanatory. The IMS bearing failures are caused by the lubricant in the IMS bearing housing leaking out or drying up and then the bearings overheating. 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.
Happily, there is a simple solution!
Porsche upgraded the IMS along with the design of the IMS bearings on 2007 model year cars onwards. For the Porsche engines fitted from 1998 to 2006/07, there have been many aftermarket solutions to address the issue We have fitted and assessed many of these solutions. So, when should the IMS bearing be replaced on a Porsche? From an engineer’s point of view, asap really! There is a school of thought that if it has lasted 23 years, it should be fine. However, if you weigh up the cost of prevention versus cure, most people would recommend prevention is preferable. Especially as the consequences of the IMS bearing failing are horrendous, and can easily cost upwards of £10,000. Furthermore, in some extreme circumstances, the engines can be damaged beyond repair and so a replacement needs to be sourced. The IMS bearing can be upgraded whilst replacing your clutch, with very little extra labour cost. It costs approximately £600 plus VAT to do an IMS bearing upgrade at the same time as a clutch change. So, it is a pretty simple equation, circa £2k for the clutch and IMS upgrade, or a costly engine rebuild? Our technicians have over a decade of experience with installing IMS upgrades and we also have the specialist engine tooling required to carry out the work properly. IMS bearing replacement options are plentiful and the option we recommend is a tried and tested part supplied with a 5-year warranty and additional oil feed to circumvent the issues we have looked at above.
If you would like a formal quote and to book your Porsche in for an IMS bearing upgrade, contact the workshop today on 01296 663 824.