Heres the deal during the winter the heater stoped blowing hot air. My dad replaced the thermostat and it didnt do anything. now the car overheats but mainly when you go over 50 miles an hour. Im planing on changing the thermostat again and changing all the fluids. Im also checking the heater core this weekend to see if its stoped up. Anybody got any ideas?
Oh yeah and its a 99/3.8 Thanks

 

Sounds like the water pump is out. Unhook the upper radiator hose and watch the temp gauge till it starts to go over normal, if it's not spraying water when the fan comes on then change the pump.

 

I changed the pump and the thermostat but the temp guage still gos above normal but it goes up and down

 

Sounds like it has a blown headgasket,3.8's are know for that.

 

I agree

 

Unless your oil looks milky, I would think it is more probable that its your heater core that needs replaced.

 

On those engines the water goes directly into the cylinder, it will not show up in the oil.I think its number one cylinder.

 

Are you loosing coolant at all? If not then I wouldn't be worried about a head gasket. ..you can check your spark plugs to see if there are deposits from burnt coolant.

Sounds like you're on the right track with the heater core. I wouldn't be to quick to tear your heads off for a gasket like others are suggesting.

 

Only the single port 3.8L cars had the known headgasket issues.
This is a '99, so it's not one of those by default (though it very well could be the issue here).
If your heater core is blocked/leaking, it won't show up as overheating unless it's dumping all your coolant out. Heater core is a side loop, and not part of the main circulation going on. If you really want to isolate it, just by pass the heater core at the firewall with a length of high temp hose.

 

the heater core is probably not the source to your overheating if its not leakin coolant then i would try changing the thermostat again might be faulty but if it had a blown head gasket it would most likely had have a miss to it but not always so prob not the head gasket