Engines · Porsche
Porsche M97 flat-six common problems
The M97 is a development of the M96 water-cooled flat-six, a naturally aspirated petrol engine in 2.7, 3.4 and 3.8-litre forms, built from 2004 to 2008. It powered the 997 Carrera S, the first Cayman and the later 987 Boxster, and was replaced by the 9A1 direct-injection engines from 2008.
Common problems and what to look for on the M97
The known issues most worth checking when you view a car with this engine. None of them means a car is a bad buy, but they're worth knowing about before you buy, and a good history often shows they've been dealt with.
Cylinder bore scoring
What to look for: Before starting, wipe inside each tailpipe with a white cloth. On a 911, a sooty left-hand pipe next to a clean right-hand one is the thing to note. Start from cold and listen at the back for a rhythmic tick or knock at idle. Ask how much oil the car uses and whether that has been rising.
Why it matters: Scoring of the cylinder walls lets oil past the pistons and is progressive. It affects a minority of engines, the 3.8 in the 997 and the 3.4 in the Cayman S and 2007 to 2008 Boxster S more often than the 2.7. It usually starts on cylinders 4 to 6. A tick on its own isn't a diagnosis, but with uneven soot or rising oil use a borescope inspection by a specialist is essential, and it's worth doing on any 3.8 or 3.4.
The intermediate shaft (IMS) bearing
What to look for: Ask for the engine number before you travel, and look in the history for any work on the bearing. With the engine running, listen at the back for grinding or rattling that changes with revs.
Why it matters: Most M97 engines have the larger bearing introduced for the 2006 model year, which is stronger than the earlier types though not immune. It can't be replaced without splitting the engine, so on these cars it's a question of the engine's health rather than a planned upgrade. The exception is early 997 Carrera S 3.8 engines up to number 68509791, which have the earlier, serviceable single-row bearing that is often upgraded at a clutch change. The engine number tells you which, not the model year.
The air oil separator
What to look for: Follow the car or have someone watch the exhaust, and note any blue smoke on start-up or in normal running. Ask whether the separator has ever been replaced.
Why it matters: A failed separator lets the engine draw oil into the intake and, at worst, can fill a cylinder with oil. It's a known replacement part, but it should be diagnosed before buying because its smoke can be confused with bore scoring.
More known issues, covered in the full guide for each car
- Rear main seal leak
- The over-rev record
Cars with the M97
- Porsche 911 Carrera 997.1: Carrera S, Carrera 4S and Targa 4S 3.8 (M97/01), 2004 to 2008
- Porsche Cayman 987.1: Cayman S 3.4 from 2005 and Cayman 2.7 from 2006, to 2008
- Porsche Boxster 987.1: Boxster 2.7 and Boxster S 3.4 from the 2007 model year
A pre-purchase inspection guide for your car
The CrankSight guide is a pre-purchase inspection (PPI) you do yourself, written for the exact model and generation you're viewing. It walks you round the car on your phone, with every check for that version, engine included: what to look for, where to find it, and what anything you find is likely to cost. As you go it builds an assessment of that car, and if you view more than one, it lines them up side by side.
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General points for the engine, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with any manufacturer.