RAMUS INSIGHT
It’s one of the most talked-about issues in the 911 world. Here’s the straight version.
If you own a 997 — or you’re thinking about buying one — the IMS bearing will come up. It comes up in forums, in pre-purchase inspections, and in workshops like ours with regularity. Most of what’s written about it is either alarmist or incomplete. This is the version we give to customers in the workshop.
What is the IMS bearing?
The intermediate shaft (IMS) sits at the rear of the M96 and M97 flat-six engines, driving the camshafts via a chain. At the flywheel end, it runs in a sealed ball bearing. That bearing is the problem. Porsche’s design didn’t provide it with a constant oil supply — it relies entirely on its own internal grease — and over time, that grease degrades and the bearing begins to wear. When it fails, the consequences are severe: loss of camshaft timing, bent valves, and metal debris through the engine. In most cases it means a full engine rebuild or replacement.
Which 997s are affected?
The issue applies to 997s fitted with the M97 engine — that’s all 997.1 models (2005 to 2008) and some early 997.2s up to 2009. The 997.2 from late 2009 onwards moved to a direct injection engine (MA1) with a revised bearing arrangement that resolved the problem. The GT3 and GT2 variants used a different engine spec and are not affected. If you have a standard 997.1 Carrera, Carrera S, Targa, or Cabriolet, the IMS bearing is relevant to you.
What are the symptoms?
The difficult truth is that IMS bearing failure often gives very little warning. Some owners report a metallic rattling from the rear of the engine, oil leaks around the rear main seal area, or metal particles visible in the oil filter at a service. In many cases there are no symptoms at all until the bearing fails completely. That’s what makes it so important to address proactively rather than reactively.
What can be done about it?
The sensible approach on a 997.1 with an unknown bearing history is preventative replacement. The bearing is accessed when the gearbox is removed, which is a significant job in itself — but if the gearbox is coming out for any other reason (clutch replacement, for example), the additional cost of doing the IMS bearing at the same time is modest compared to the alternative. Aftermarket ceramic hybrid and full-complement roller retrofits address the original design’s weaknesses directly and are what we recommend at Ramus.
If you’re buying a 997.1, the first questions to ask are whether the IMS bearing has been replaced, what it was replaced with, and whether there’s paperwork to prove it. A specialist pre-purchase inspection that checks the oil filter for metallic debris is also well worth the investment.
Should it put you off a 997?
Not at all — a properly maintained 997 with an addressed IMS bearing is one of the greatest driver’s cars ever made. The issue is manageable. What matters is knowing the history of the specific car, and acting on it if you don’t. We see plenty of 997s in the workshop and the ones that have had the bearing done correctly give their owners years of trouble-free driving. The ones that haven’t can be an expensive lesson.
If you’d like us to inspect your 997’s IMS bearing status or discuss your options, get in touch with the team.
