Porsche 928/944/968 Running Hot Problems

If your 928/944/968 is running hot no matter what you have done, the problem most likely lies in the rubber grommet behind the thermostat. The 928/944/968 thermostat works differently than most other cars. When it is closed, during warm up, the coolant is directed through the block to eliminate hot spots. When the thermostat opens, the large disc on the back of the thermostat seals against the rubber grommet behind, sealing off the bypass passage and directing coolant into the radiator. Remember coolant will take the path of least resistance, hence back into the block, not the radiator and the resulting problem is that your car will run hot.

The rubber grommet rots over time and causes a bad seal. This grommet is not hard to replace. It should be replaced every time a thermostat is replaced. This is also a good time to flush out the cooling system and add good antifreeze.

Also, if it is a 944/968, replace the auxiliary coolant fan switch. In the shop whenever a thermostat is changed the fan switch is also (if applicable). We have had too many incidents where we would change a thermostat and the fan switch would fail a couple of days later.

Better to be safe, and it will save lots of money if you overheat your engine.

The part numbers for the sealing ring are as follows:

944/968 - 951 106 155 00

928 - 928 106 163 00.

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