Common engine faults
The typical problems affecting water-cooled Porsche engines from 1997 to 2008, what each one is, and what we do about it. Written from the engines we strip, with photographs of the actual damage rather than diagrams.
Not sure the fault is inside the engine? Neither are we until we have checked. Every rebuild starts with a first assessment: oil analysis, cylinder bore imaging, a DME read-out and a combustion gas test. Several cars have arrived here for a rebuild where the fault lay elsewhere. How the assessment works.
IMS bearing failure
Boxster 986 and 987, Cayman 987, 911 996 and 997, 1997 to 2008
What it is
The intermediate shaft in the M96 and M97 engine runs on a sealed ball bearing that was too small for the job. It wears, sheds metal particles inside its own grease, and can fail outright. Failures were seen anywhere from around 45,000 miles upwards, while other engines ran far longer without trouble.
What you may notice
Metal debris in the oil filter is the usual first evidence.
What we do
During a rebuild we fit the later, larger Porsche bearing where the engine can take it. For engines that cannot, we now offer an exchange intermediate shaft with a larger, stronger bearing. Neither is done blind: the shaft, its housing, chains and guides are checked with the engine apart.
Bore scoring
Mostly the 3.4, 3.6 and 3.8 M96 and M97; scoring and seizing is also seen on Gen 2 9A1 engines
What it is
Scored or scuffed cylinder walls in the original Lokasil bores. Once a piston and bore have scored the engine will often run for another ten to thirty thousand miles, but oil consumption rises and piston slap becomes audible as a knocking noise.
What you may notice
Rising oil consumption and a knocking noise from the affected cylinder.
What we do
We machine out the original cast-in liner and fit our own closed-deck Nikasil-plated aerospace-alloy cylinders with matched forged pistons, on all six cylinders, not just the one that failed. The cylinders convert the block from open to closed deck, which also stiffens it.
Cracked cylinders and liners
M96 and M97 engines
What it is
Cracking and ‘D-chunking’ of the cast-in Lokasil cylinder, where a section of the liner breaks away. Cast-iron sleeving is a cheaper repair we ruled out years ago: iron expands differently from the alloy around it, transfers heat less well, wears faster, and we have re-rebuilt engines repaired that way after they failed again.
What we do
All six cylinders are replaced with Hartech closed-deck Nikasil liners with matched pistons. A strengthened cylinder is guaranteed against cracking.
Crank bearing failure
M96 and M97 engines
What it is
Main and big-end bearings wear through their overlay, and the debris then circulates through the oil system and into everything else.
What you may notice
Bearing material in the oil filter and pickup.
What we do
New crankshaft main and thrust bearing sets and new big-end bearings are part of every rebuild package. On block-only work we insist on fitting our own performance crank bearings.
Timing chain failure
M96 and M97 engines
What it is
Chains stretch, sprockets wear and the plastic guide rails break up. Early roller chains suffer more than the later Hivo design. A snapped chain stops the engine and usually damages it.
What we do
A new timing chain set with new guide rails goes into most rebuild packages, and the chain drive is inspected on every engine we strip.
The long version
Barry Hart’s report The main problems with Porsche engines covers the three main failures of the M96 and M97, the cylinder scoring seen on Gen 2 9A1 engines, the basic engineering factors behind them, and the reasoning behind Hartech’s solutions. It runs to 174 pages, with a short version at the front for those who want the conclusions without the detail.
Download the report (PDF, 8 MB)
The JayEmm on Cars explainer, filmed here, covers the same ground in 40 minutes with Barry at the bench.
Describe what your car is doing
Symptoms, noises, mileage and any diagnosis you already have. We will tell you honestly whether it sounds like one of these, and what we would check first.
01204 302 809
Option 1 for engines, option 2 for servicing and the workshop
- Open
- Mon–Thu 07:15–17:45
- Closed
- Fri, Sat, Sun, bank holidays
- Drop-off
- Before 17:00; locking up starts 16:45
- Address
- Firwood Industrial Estate, Off Thicketford Road, Bolton BL2 3TR