Yesterday while topping up my screen wash I noticed that I have oil in my coolant tank so I took the car to a mechanic that has said it doesn’t seem to be the head gasket as it’s not showing signs to be it as the car doesn’t overheat, no water in the oil, no smoke blowing from the exhaust etc however he thinks it could be down to the Thermostat as it has oil leaking from it.

My question what are the chances of it being the thermostat housing? I did take it to 2 other garages that just said it was the head gasket.


To my knowledge, the thermostat not only has nothing to do with the oil, oil isn't and shouldn't be anywhere near it (as far as the engine is concerned). The coolant and oil should be two separate systems ... narry the two shall meet. If they do, then there's something wrong. Just because it isn't overheating doesn't mean there isn't a problem with the head gasket or some other gasket allowing oil to be pumped (or seep) into the coolant system. It could also be an oil cooler leaking into the coolant system. Lots of reasons there could be oil in the water, but none of them would include a thermostat.

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  • Perhaps the "thermostat gasket" in this case is actually a gasket in an oil/coolant heat exchanger, and the thermostat is mounted in it or near by. – DavidSupportsMonica Oct 3 '19 at 14:53

I had the thermostat gasket replaced along with my coolant being flushed out and it seems to have solved the issue, I’ve had water added to my system rather than coolant to see how it goes..

Been running for a week from today with no issues

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