Or, in other words.. Purge all the air from the cooling system.
You shouldn't have to do this is you use the air cap (screws out of the passenger side of the radiator), and have some patience and SLOWLY fill the coolant. If you see it fill up to the radiator neck youre not done. Wait for it it go down. This will start to happenpre and more frequently. It takes more than just a few minutes. After it's pretty much full and you can't get anymore in at all, close the cap. Then FILL the overflow bottle to the top. Drive the car until it gets up to normal op temp. Then shut the motor off until it cools ALL the way down. This will allow the system to depressurize and create a vacuum. This will pull coolant out of the overflow bottle. Keep an eye on it. It will either get really low or empty out depending on how patiently you poured coolant in the radiator. Fill it up here and there. After driving a few times it should stop pulling any extra antifreeze at all and start to normally fill and drain.
Okay, so here's what I want you to do. As soon as the temp rises up while driving, shift down until the motor is revving ABOVE 3500 (4000 RPM at the MOST) RPM. This will flow enough coolant through an OPEN thermostat to cool an engine with bad head gaskets or a bad thermostat. Any other issues, and it won't cool down. If it doesn't work at first, try a few more times. Keep the heat ON and at full "defrost." drive like this for a while. Does it cool down? And how long does it take? What does it do with the heat and everything completely off?
After you start driving like normal, how long does it take to overheat again (while drving) if it cooled.
Why speeds does the overheating occur?
Which water pump do you have? The one where the thermostat is mounted vertical or horizontally?
How long does it take for it to start overheating when you FIRST drive it for the day?
How long does it take to overheat when you drive it after you've driven once or a few times?
Have you replaced the thermostat before?
Last edited by Kennyfvholla; 11-11-2012 at 08:45 PM..