The IMS bearing and bore scoring are two separate faults found in some water-cooled Porsche flat-six engines built from the late 1990s to the late 2000s. Neither affects every car, both can be assessed before you buy, and both are far easier to live with when you know where a particular car stands.
What the IMS bearing is
IMS stands for intermediate shaft. In these engines the shaft drives the camshafts, and one end of it runs on a sealed ball bearing.
When that bearing wears, it can shed debris into the oil and, at worst, let the cam timing slip. That can destroy the engine with little warning.
It applies to the 986 and 987 Boxster, the 987 Cayman and the 996 and 997 Carrera, roughly model years 1997 to 2008. Turbo, GT2 and GT3 models of those years use a different engine and are not affected.
What bore scoring is
Bore scoring is damage to the cylinder walls: vertical scratches where the piston has scuffed the bore. It tends to get worse, not better.
It is most often reported on the larger engines of the same era, and cold starts are widely believed to play a part, which matters in a city with winters like ours.
- A ticking or knocking at idle, often on one side
- One tailpipe sootier than the other
- Oil consumption that keeps rising
How each one is checked
Neither fault should be guessed at. This is what an assessment looks at.
Service history
Has the bearing been inspected or replaced, and is there an invoice that says so?
Oil and filter
Metal in the oil filter is an early warning worth acting on.
Bore scope
A camera in the cylinders shows the walls directly. We use a bore scope where warranted.
Compression and leak-down
Compression and leak-down where warranted, as part of the engine and drivetrain checks.
Fault memory
A full-system scan with factory-level tooling, including stored and pending codes.
Road test
Cold start and full operating temperature, listening for the noises that matter.
If you own or are buying one
These faults are a reason to buy carefully, not a reason to avoid the cars.
Buying: have the car inspected first. Our pre-purchase inspection includes known-fault checks for your specific model: IMS, bore scoring, timing chains, water pumps.
Owning: keep the oil fresh, warm the engine before working it hard, and have odd noises looked at early. If an engine needs work, we rebuild it in house.
Questions owners and buyers ask
Do you check for IMS bearing and bore scoring problems?
Yes. Known model faults such as IMS bearings and bore scoring are part of our pre-purchase inspections, and we assess them on customer cars when the symptoms point that way.
Which Porsches have an IMS bearing?
The water-cooled flat-six engines in the 986 and 987 Boxster, the 987 Cayman and the 996 and 997 Carrera, roughly model years 1997 to 2008. Turbo, GT2 and GT3 models of those years use a different engine.
Can bore scoring be seen without taking the engine apart?
Usually, yes. A bore scope passed into the cylinders shows the condition of the cylinder walls. It is part of our pre-purchase inspection where warranted.
What happens if the engine does need work?
If an engine needs work, we rebuild it in house. In a corrective rebuild, known weaknesses are engineered out so the engine goes back together stronger than the factory sent it out.
Should these faults stop me buying one of these cars?
No. They are good cars. The faults are a reason to buy with an inspection and a service history, not a reason to avoid the model.
