my compression is fine no evidence of oil in water or water in the oil but it still every now and again pushes air back into the expansion bottle and over flows also does the ecu control the radiator fan kicking in as ive never heard it run but i do know it works and the temp gauge reads never more than a third up the dial and even after ive replaced the sender.

Mick, June 2006

Usually if its a blown headgasket you can see bubbles in the overflow ....heater won`t work either ..possiable bad therm or a bad radiator not leting coolant flow

bg, June 2006

It sounds like you have a faulty thermostat. Fans usually only kick in when the engine is up to working temperature and the vehicle is stationary. It looks like your never gets up to working temp and so your fan will never kick in. A faulty stat may also explain a sudden rush of water.

BTW as you don't say what the car is, no one can answer your question about the ECU even if it was the problem.

Terry, June 2006