Quote:
Originally Posted by scrambledeggs728
Saw a listing for a 2003 S with a replacement m97 due to earlier IMS failure; when searching I found a Jake Raby post saying the m97 bearing has no spotted failures except for tracking (since they redesigned it to last under street driving instead of racing, like the earlier). My local mechanic says not to trust it despite that, that the m97 2005-8 was designed to avoid in warranty failures and that is why eventually the IMS got removed; and that anyone, if they had their m97 engine apart, would replace the bearing anyway even if never "tracked".
In any case, in general is a replacement m97 engine in a 986 like the listing above, a good or neutral or bad sign? |
They're both right and maybe a little wrong. The Gen III IMS bearing (mid 2005-2008) has approx a 1% chance of failing. To replace it, you need to totally disassemble the engine halves to do it properly (there are some procedures where they're drilled out). But for the most part, the GIII IMS is reliable. Your mechanic is right from the standpoint that it is a bearing and ALL bearings eventually fail but this version should last 200K+ mi. There's a lot of speculation why IMSs fail, but tracking your car at DEs is generally not thought to be a reason IMS fail. Low mileage cars that sit for long periods of time have a high rate of failure. The other item that seems to correlate to failure is oil change intervals. You're ideally looking for changes every 5-8K mi. Anything longer could be an issue as the IMS is bathing in dirty oil. I've given a very high level answer, if you want more detail there is plenty of info on IMS here in archives.
I would be more concerned about the electronics than IMS. The M97 would be using a different ECU and would have different features / functions than a 2003 had. You'll want to be sure all the electronics are sorted. Can be done, but would be a big job.