That's hardly a fix but it could indeed get you by for a little while. You didn't say which engine you have. Some of them have thermostats with small bleed holes already. Thermostats open in response to hot liquid, not hot air. Those bleed holes are there to allow a very small flow of coolant so the hot liquid can get over to the thermostat sooner and cause it to open. When there is no bleed hole it's because due to the engine design, it isn't necessary. The thermostat sits very close to where the heat is being generated. The problem is when you have a leaking head gasket that allows combustion gases to enter the cooling system, that air pools under the thermostat preventing it from opening. That results in overheating which can warp a cylinder head and aggravate the problem.
Look for a bleeder screw on the thermostat housing. If there is one, there's no hole in the thermostat already. If there's no bleeder screw, look for a hex plug or a coolant temperature sensor on or near the housing. After running the engine a few minutes, remove one of those things and watch if any air comes out. If you immediately get liquid, there was no air under the thermostat. If you do get a bunch of air, it was trapped there because there's no bleed hole in the thermostat.
Jan 11, 2013 at 10:29 PM
