2002 Chevy Cavalier

Have the cap tested to be sure it can hold pressure. If it is ok, you may need to have the cooling system chemical tested for exhaust gasses (bad head gasket). Do you have the proper coolant/water mix or is it just water in the cooling system? I just water it will boil at this temp causing the excessive pressure to be let out at the cap

Are you using coolant or only water? Also, I need you to check some things. First, is there any coolant mixing with the oil? Any oil mixing with the coolant? Also, check the front corners of the cylender head for evidence of coolant leaks. Finally, with the engine cold, remove the radiator cap and start the engine. Does any of the coolant come shooting out?

Sorry for all the questions, but based on what you replaced, I really am thinking you have a bad head gasket and that is causing the problem. If coolant is forced from the radiator when it is cold and you just start the engine, that tells me compression is making its way into the system.

Let me know what you find. Also, check closely for evidence of leaks around the head. Most common spot is the driver's side front of the engine for leaks.

Joe

I would think so. Since water boils at 212 and coolant will go to 275, that may be part of the problem. Are you sure there are no leaks around the head?

I would recommend trying one more thing before installing the coolant. Pressure test the cooling system so you can check for leaks. You will need a pump to do it. Most parts stores will lend or rent them to you. It is nothing more than a hand pump that screws on to where the rad cap is. Pressureize the system and check for leaks. If there are none, the I recommend installing a 50% coolant and 50% water solution into the engine to see if that takes care of the problem.

Let me know what you find.

Joe