The IMS (intermediate shaft) bearing supports a shaft that drives the camshafts on the M96 and M97 flat-six engines. It can fail without much warning, and when it does, the engine is usually ruined. It affects 996s, 997.1s, 986 Boxsters and 987.1 Boxsters and Caymans, but not the Mezger-engined Turbo, GT2 and GT3.
It's the question I'm asked most about water-cooled Porsches. Here is the honest version.
Which Porsches have an IMS bearing problem?
- Affected (M96/M97): 996 Carrera (1997–2005), 997.1 Carrera (2004–2008), 986 Boxster (1996–2004), 987.1 Boxster and Cayman (2005–2008).
- Not affected: 996 and 997 Turbo, GT2 and GT3 (Mezger engine), and all 9A1-engined cars from 2009 onwards, which have no intermediate shaft.
How common is IMS bearing failure?
Far less common than forum noise suggests. Most estimates put it in the low single digits as a percentage, with the 2000–2005 single-row bearing at higher risk than the earlier dual-row type. That is still enough to take seriously when buying.
How much does it cost to replace an IMS bearing in the UK?
At a good independent specialist, an upgraded IMS bearing fitted alongside a clutch change typically costs around £1,500 to £3,000*. Doing both together makes sense, because the gearbox has to come out for either job. A failed bearing that has damaged the engine is a different conversation: often a rebuild, or a replacement engine.
*Indicative, depends on the car and the specialist.
Should I avoid a car with an IMS bearing?
No, but buy it properly. I'd look for evidence of an upgraded bearing (with invoices), a clean oil-filter inspection, regular oil changes, and a car that has been driven rather than stored. If none of that exists, I'd price an upgrade into the deal.
What are the warning signs?
- Metallic debris in the oil filter at service time.
- A rattle or grinding from the rear of the engine.
- Oil leaking from the IMS cover flange.
- Cam deviation fault codes on a diagnostic scan.
Every water-cooled car I offer comes with its IMS position stated plainly. See the current cars, or book a consultation if you're looking at one elsewhere.
Quick answers
What is a Porsche IMS bearing?
The intermediate shaft bearing supports the shaft that drives the camshafts on M96 and M97 flat-six engines. If it fails, it usually destroys the engine.
Which Porsches are affected by the IMS bearing?
996 Carrera, 997.1 Carrera, 986 Boxster and 987.1 Boxster and Cayman. Mezger-engined Turbo, GT2 and GT3 models and all 9A1-engined cars from 2009 are not affected.
How much does it cost to replace a Porsche IMS bearing in the UK?
Typically around £1,500 to £3,000 at a good independent specialist, usually done alongside a clutch change because the gearbox has to come out for both.
