i'm doing an import at the minute for overheating, the rad and thermostat have been changed there is no leaks and it's just had a new waterpump fitted but when on idle after a run the gauge goes up to 3/4 and the select moniter registers nearly 120 degrees. the expansion bottle overflows and there are bubbles so i'm pretty sure the head gaskets are gone but why is it the rad stays cold? there are no airlocks in the system but the only hot part of the rad is the end the top hose is at. put your hand on the core directly next to it and it's cold from there to the other side and so is the bottom hose. yet the fans run all the time, it's almost like the water isn't circulating. does the compression gas cause an airlock in the system thus stopping the water circulating?

 

I have had no end of similar problems, I have changed my head gaskets and same result, fitted a brand new thermostat, same result, new temp sensor, same result.

Solution: I removed the thermostat, no more overheating and the engine runs sweet, has done for over a year now (about 16 months).