First of all, is the electric radiator fan turning on? You didn't say which engine you have. Some have a bleeder screw on the thermostat housing. If there isn't one, look for a temperature sensor or threaded plug you can remove to bleed any air pockets out while you refill the system. Thermostats don't open in response to hot air. They must be hit with hot liquid.
You also didn't list the symptoms. If you're seeing bubbling in the coolant reservoir as soon as you start a cold engine, you know it can't really be overheating that quickly. Suspect a leaking cylinder head gasket. Your mechanic can do a chemical test at the radiator or reservoir to verify that. An additional clue is there won't be any steam associated with that bubbling.
I can suggest some relatively obscure things too if it comes to that. When did this overheating start; Before replacing the timing belt or right after replacing it? Does your engine use a timing belt or timing chain? If it uses a belt, is the water pump driven by that belt? Does the overheating occur only at highway speeds, only at slower speeds, or both?
Sep 21, 2013 at 3:57 PM
