i recently bought a 1995 lumina that overheated. i changed the thermostat and it drive for 3000 miles then overheted again. i changed thermostat again and it changed nothing . had water pump looked at and changed still over heating. like it is loosing coolant but no leeks on the ground. the temp will rise and fall pushing hot air out the vents when falling. i am at my wits end with this i don't know what to look at next or what the problem could even be ! does any one has any ideas ?

 

Did you use the bleeder valve to get rid of any air pockets?

 

yeah i was hip to all that blead out air just had intake manifold gasket changed it still act funny and heat is still riseing and falling on temp gauge i really don't know hwere to go from here. thermostat, water pump i guess the next thing would be a new radiator ugh.

 

You didn't mention changing the rad cap, maybe try that first before getting a radiator.

 

I also have a 95 monte carlo had this same problem turned out to be a cracked head, I replaced the engine good luck.