Engine Cooling

Thermostat O-Ring: Warning!

Thermostat O-Ring: Warning!

I have been working on my 88S4 project car, to the point where I just got the intake manifold re-installed and am working on other engine attachments. I knew this car would be a project due to the purchase price and a cursory examination of the condition of the engine compartment. Despite the presence of one beautiful Devek radiator, the engine compartment appeared to have been hotter than normal for an extended period of time, based on the deteriorated condition of compartment wiring. I just found the problem, which I am passing along for your entertainment. Perhaps this story may help someone else.....

The thermostat in a 928 closes a water passage when the engine reaches operating temperature, thus forcing coolant through the radiator where it is cooled significantly. Well, whoever installed the last thermostat in this 88S4 put the large o-ring in the housing UNDER the thermostat, holding the thermostat approximately 1/8 inch farther away from the seat than intended. This appears to be enough that the full coolant flow through the radiator was never achieved, so the engine ran considerably hotter than it should have.



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