Written by Adrian Harkin 11/08/2024

The front engine Porsche engine range share a host of common parts and possible problems. I’ve tried to break them down here to the most common issues that arise. These are very strong engines that provide superb power delivery, and long life. Failures are usually avoidable and in most cases are predictable. 

Cam Belts

The cam and balance belts in the four-cylinder cars once snapped can cause severe engine damage. None of these engines are a “free spinning” engine. The rollers, belt condition and tension should be checked at every service. Replacement of these belts should be carried out at no more than 60,000 km or five years, whichever arrives first. At this time it is important that the tension and idler rollers be replaced accordingly. The water pump is driven by the back of the cam belt and this too can cause premature belt failure if worn, and should be replaced with the belts. On the four cylinder engines, the balance shaft belt is just as important as the cam belt. If poorly timed or snapped, the vibrations it would normally cancel, can lead to the oil pump pick up fracturing and breaking off. Also, I have seen the alternator and A/C compressor brackets break off if this problem is not attended to due to their mass.

Cam Chains

In all twin cam engines, 944 S, S2 and 968, and the 928 32V & S4 the inlet cam shaft is driven by a chain from the exhaust cam shaft. This chain is tensioned by a unit mounted between the two camshafts, the chain running on two nylon tensioner pads. Porsche does not have any servicing requirements for these items. Unfortunately although owners have been made aware of the need to change cam belts regularly, this chain and tensioner assembly appears to have been ignored. In real life the cam chain starts to stretch and the nylon pads wear down. This causes excessive angle of attack at the base of the sprocket teeth on the camshaft, greatly shortening the life of the cam itself and worst case scenario is that eventually the sprocket teeth become so badly degraded that the cam timing slips and causes serious engine damage. Although it may be possible to change the worn cam chain and tensioner pads before they fail. The wear on the sprockets often requires that the camshafts have to be replaced as well. It is a good idea that they be inspected at the same time as the cam belt is replaced

Oil Cooler

The oil cooler in pre 1989 model cars and non-turbo engines is a water to oil heat exchanger, integral to the engine rather than the traditional external air to oil coolers as seen in the turbo and S2 engines. This small radiator sits in the coolant jacket of the engine itself. The oil cooler is sealed by two small O-rings, if these fail, oil is forced into the coolant creating a brown sticky emulsion that will cause serious damage to the cooling system and oiling system  if left unattended. 

The 928’s utilize a similar system for the engine oil and also the automatic transmission fluid, though the cooler or heat exchanger lives in the side tanks of the radiator itself. As the radiators age these coolers can and do fail causing an oil water intermix. This can cause considerable damage to the engine and transmission very quickly. The adhesive used to hold the friction material on the transmission bands and clutch packs is water based. Most Australian market cars have another external air to oil transmission cooler in front of the radiator as well. Australia’s mild to warm climate means these heat exchangers are generally unnecessary and easily bypassed to the external cooler or replaced with air to oil coolers if desired. 

Head Gaskets

As these all-alloy engines heat up and cool down the continual expansion and contraction compresses and stretches the head gasket till it eventually fails or simply rots away. This is usually noticeable if the car is running hotter than usual or there is an excessive pressure in the top radiator hose. Left unattended these faults can become serious, but a replaced head gasket will last a very long time.

928’s, like the four-cylinder engines, are a very overdesigned unit. Though given the nature of the car and the prodigious torque, they are very under stressed. Because of that over design, they don’t wear out, a large number of 928’s have never had their cylinder heads removed, even at nearly forty years of age. Head gasket failure on the 928’s is generally different to the four cylinders. The usual mode of failure can cause catastrophic damage to the engine. The head gasket will rot away, leaving only the steel firing ring, this eventually will deform weakening its seal. Once the engine is switched off, the hot pressurized coolant can then leak into the combustion chamber, usually filling it. Then the next time the car is started that cylinder will hydraulically lock and when another of the eight cylinders fire, it will split the bore. This damage renders the engine block unrepairable. 

This failure mode can also happen to the 944, but having only three other cylinders generally means the engine will just stop cranking as the effected cylinder hydraulic locks.

Preventative head gasket replacement on these cars is very important if we want them to survive  into the future.

Vibrations and Engine Mounts

The clutch centres on the naturally aspirated four-cylinder engines are made of rubber, to try and absorb engine vibrations. The 968 did away with this when it went to the now common dual mass flywheel. With age, and possibly abuse, this rubber centre breaks up and can cause a very noticeable clunk on and off drive and also a noticeable vibration through the entire rev range. Most replacement clutches now come with a spring centre, so once replaced the problem won’t happen again.

The engine mounts on all these cars are of the hydraulic or “silent bloc” type. These eventually leak and collapse. The right hand side usually fails first, as it has to deal with the added heat of the exhaust as well as the torque of the engine. This failure is usually most noticeable at start up, going away at higher RPM. An easy way to quickly check the engine mounts is to rev the engine by hand in the engine bay and watch. If the engine rocks left to right, then the mounts still have enough fluid in them to support the engine. If not, then the engine is effectively solidly mounted to the vehicle and the mounts should be replaced.