Porsche IMS Bearing: Which Cars, How to Check, What It Costs

Which Porsches are affected

Model-year boundaries are approximate around generation changes; the engine number and build date decide which bearing a car has.

The intermediate shaft links the crankshaft to the camshaft chains, and it rides on a sealed ball bearing. If that bearing breaks up, debris spreads through the engine and cam timing can slip, which usually means a rebuild or a new engine. Bearing design changed over the years: the 1999–2000 double-row part has the best record, the 2001–2005 single-row part has the worst, and the larger 2006–2008 bearing rarely fails. Turbo, GT2 and GT3 models use a different (Mezger) engine and are not affected, and the 997.2 and later 9A1 engines have no intermediate shaft at all.

Bearing types by year

Boxster and Cayman cars follow the same design changes; the stronger bearing arrived around late 2005/2006 production.

Symptoms and how to check before you buy

Failures often give little warning. What to look for:

• Often none before failure
• Metal debris in the oil filter or on the drain plug
• Rattle or ticking from the rear of the engine
• Cam deviation fault codes

Pre-purchase checks:

• Ask for invoices showing an aftermarket bearing retrofit or a full replacement solution
• Have the engine number checked to confirm which bearing type the car left the factory with (PCA can help)
• Inspect the oil filter for metal during a pre-purchase inspection
• Note that many cars already got factory replacement engines, which changes the picture

A full checklist for these cars is in the Porsche pre-purchase inspection guide.

Retrofit and repair costs

About $3,000 for a preventive bearing replacement with clutch disc; $20,000–$30,000 for an engine overhaul after a failure. Because the clutch and the IMS bearing are both reached with the gearbox removed, doing the bearing at the next clutch job keeps labor down. An IMS retrofit does not address bore scoring or other M96/M97 weak points.

Porsche settled an IMS class action in federal court in California (Eisen v. Porsche Cars North America, No. 11-cv-9405). It covered most 2001–2005 Boxster and 911 models except Turbo, GT2 and GT3, and paid a share of repair costs for IMS failures within 10 years or 130,000 miles of the in-service date. The share depended on mileage and on whether the car was bought new, Porsche certified, or used elsewhere. Every covered car is now well past that 10-year window, so the settlement no longer pays for new failures.

Bore scoring: the other M96/M97 issue

Bore scoring means deep scratches in the cylinder walls. It cuts compression, raises oil use, and in the end needs a rebuild with sleeved cylinders. The exact cause is debated, but the cylinder surface material, cold starts and dirty injectors are commonly blamed. Unlike an IMS failure, it usually builds slowly and gives warning signs. The 997.2's 9A1 engine is reported to suffer from it far less often.

Scoring of the cylinder walls raises oil consumption and eventually needs a rebuild. In the Boxster and Cayman it is tied mostly to the 987.1's 3.4 S engine; one marque estimate puts it at about one in 20 pre-direct-injection cars. It is rarely reported on the 2.7.

Checks for bore scoring:

• Get a borescope inspection — specialists scope from below because scoring starts at the bottom of the bore
• Send an oil sample for analysis
• Compare soot on the left and right tailpipes
• Ask about oil top-ups between services

Both issues and the rest of each generation's watch-list are on the Porsche 911 known issues and Boxster & Cayman known issues pages.

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