What would cause a 1994 Pontiac Grand Am to over heat, after we replaced the water pump and the

[DeeDee]

What would cause a 1994 Pontiac Grand Am to over heat, after we replaced the water pump and the

thermostat? My husband Just bought this car it had a few wiring problems and from what we were told it didn't have any problems except for the wiring issues. He fixed the wiring and now it is overheating. So we replaced the water pump and the thermostsat, and its still wants to over heat. What could be the problem. He has ruled out the heater core, there is no blocking there, and he has ruled out the head gasket because it has great power and is running fine, He says its overheating almost as soon as you start the car????? Any Ideas
yes the radiator fans are all working. He is thinking the radiator may be blocked somewhere.
Well He has checked for leakes and there are no signs of any leaks but he is going to have it tested.

 

[MIGuy34]

Antifreeze might be low, or there might be air inside the raidator or cooling system inside the engine. Bleed the air out.

 

[wde3477]

Agree with MIGuy34 - the sensors do not read air temperature well, the coolant system needs to be properly purged of air, or false readings can occur. Not familiar with your particular model, but many newer cars have an air bleed port near or on the upper radiator hose outlet on the engine.

Is the vehicle truly overheating, or just indicating?

If the vehicle is really overheating, should get both the instrument panel indication, a 'check engine' light indicating a coolant temeperature fault code as well as the engine 'feeling' hotter than normal.

A short circuit (grounded signal wire, busted sensor, etc.) in the coolant temperature wiring circuit will appear like the engine is hot. It is suspicious that the overheating occurs almost as soon as you start the car and after some wiring work had been done. Perhaps something got grounded, cut, or otherwise damaged?

If the thermostat somehow was installed backwards, this could lead to overheating, but again, the overheating shouldn't take place until after the car's normal warm-up time.

 

[Goatman]

IS it actually overheating..(blowing fluid out the overflow?) or just indicating high temp on the gage?
with the radiator cap removed does the coolant spray out after only a couple of min of running from cold ? if so you may have a bad head gasket the car will still run decent as the coolant may not be actually getting into the combustion chambers yet but combustion gasses may be passing into the coolant passages ...
removing the cap and running it for a few min should blow fluid out if you have a problem ...
if you can't figure it out I suggest you see a mechanic that has the ability to pressure test it to be sure..