Porsche flat-six engine in the rear engine bay

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Porsche M96 and M97 common problems by mileage

Common problems · Porsche · 6 known issues

The M96 and M97 get a bad rap because of the IMS bearing, and it deserves the attention. But most of what these engines need is ordinary: seals, a water pump, an air-oil separator. Here's how it usually plays out.

Covers: M96: 1997–2004 Boxster (986) and 1999–2005 911 Carrera (996). M97: 2005–2008 Boxster/Cayman (987.1) and 2005–2008 911 Carrera (997.1).

When these usually show up

Routine wearFix it when it startsCan wreck the engine or gearbox

Rear main seal (RMS) leak

IMS bearing

Water pump

Air-oil separator (AOS)

Coolant expansion tank cracks

Bore scoring

0k50k100k150k200k

Miles where owners and shops commonly report each problem. Plenty of cars go longer, some fail sooner. This is a heads-up list, not a schedule.

The list, in mileage order

Rear main seal (RMS) leakRoutine wear

Usually about 30k–120k miles

Signs: Oil drip between the engine and transmission.

Very common. Usually fixed when the transmission is already out, like during an IMS or clutch job.

No price reports for this one yet. Paid for it? Add yours.

IMS bearingCan wreck the engine or gearbox

Usually about 40k–120k miles

Signs: Metal flakes in the oil filter, rattle from the back of the engine. Often no warning.

Failure usually wrecks the engine. On M96 cars the bearing can be retrofitted with the transmission out. On 2006–2008 M97 engines the bearing is larger and can not be removed without taking the engine apart.

What owners paid: non-dealer median $4,000 (5 reports). All 5 reports → · Repair guide →

Water pumpFix it when it starts

Usually about 50k–80k miles

Signs: Coolant drip under the middle of the car, coolant smell, temps creeping up.

Many owners replace it proactively around 60k because the impeller can break up.

What owners paid: non-dealer median $950 (1 report). Small sample, so treat it as rough. All 1 report →

Air-oil separator (AOS)Fix it when it starts

Usually about 50k–100k miles

Signs: Big puff of smoke at startup, high oil use, rough idle, oil in the intake.

Often mistaken for something worse. Fairly common and not a huge job.

What owners paid: non-dealer median $1,200 (5 reports) · dealer median $1,225 (2). All 7 reports →

Coolant expansion tank cracksRoutine wear

Usually about 60k–140k miles

Signs: Coolant smell in the trunk area, low coolant warning.

The plastic tank gets brittle. Cheap part.

No price reports for this one yet. Paid for it? Add yours.

Bore scoringCan wreck the engine or gearbox

Usually about 60k–150k miles

Signs: Ticking, oil consumption, sooty tailpipe on one side.

Seen on some M96/M97 engines, more often on the larger-displacement versions. A borescope inspection tells you a lot before you buy one.

No price reports for this one yet. Paid for it? Add yours.

Shop-floor advice

Cut open the oil filter at every change and look for metal. It's the cheapest early warning there is.
If you're doing an IMS retrofit, do the clutch and RMS at the same time.

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This article is general information for car owners. It is not a substitute for a diagnosis by a qualified mechanic who can inspect your car. Prices mentioned are medians of owner reports, not quotes.