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I’ve read lots about this from magazines and online forums about the M96 and M97 engines, but I’d appreciate an answer from a long-serving technician at Porsche like yourself. I’m looking to buy a 996 C4S or 997.1. Should I avoid a car that hasn’t had an IMS bearing upgrade? Or is it safe to run on the factory bearing? When was the factory switch-over from double to single row, and which is better and why? Anthony Potter
Regarding the IMS bearings, of course it is safe to drive cars with the original bearings. In fact, I have only ever seen a handful of cars which have an aftermarket bearing installed, be it an oil-fed or ceramic bearing. Often the cars with aftermarket bearings fitted suffer from oil leaks. This is only from personal experience; I’m sure there are many out there that are perfect.
However, I personally would not allow the IMS ‘issue’ to dictate the car you buy. The factory bearings can suffer failures, but in the grand scheme of things it is a rare failure, and of course you would only ever hear about the ones that have failed, which is a very small percentage of cars out there.
I’ve seen cars maintained perfectly with failed bearings and, likewise, neglected cars where the bearing is fine. I think it’s a case of bad luck if it fails. Otherwise, both the 996 C4S and 997.1 are great cars, so you’ve a difficult choice on your hands!