I am up for any suggestions

[Jodi77]

I have a 98 cavalier. I changed the waterpump and the thermastat twice and my car still overheats. when the thermastat is in there is no flow going through the hoses and it over heats but when you take the thermstat out and run the car theres flow and it doesn't over heat.
Whatelse could be wrong with it?

[curtis73]

First of all, how hot is it getting?

If the temp guage says over 230, then yes, its overheating. If the radiator cap is blowing steam, then its possible that its just a bad radiator cap.

If the hoses aren't getting hot, then the thermostat isn't opening. That means either its a bad thermostat, or its not overheating. bad gauge, bad radiator cap, plugged radiator all top my list.

[Airjer_]

What engine?

If its a 2.2 I would consider the posibility of a head gasket failuer. Air bubbles are introduced into the coolant through the bad head gasket and collect under the t-stat. The t-stat doesn't work if its not in coolant.

If its a 2.4 I feel sorry for you. These are a real PITA to blead the air out of. I bought a tool that sucks the air out of the cooling system and puts it into a vacuum then allows coolant to be added. It eliminates the majority of the air pocket problems.

[curtis73]

Yeah, a little more info would be great.

Is the radiator (or surge tank) boiling over?
What does the gauge say?
Which engine?
How do you know its overheating?

[MagicRat]

Originally Posted by Jodi77

I changed ... the thermastat twice

This may be obvious, but did you install the thermostat backwards?
It's an easy thing to do, but if it's backwards, it will never open and your car will overheat.
The side with the spring in it must point towards the engine so it is immersed in the hot coolant.