when im driving heat is blowing out nice and hot...when im stopped it turns cold...topped off antifreeze,.... had changed intake gasket due to leak and little sensor on firewall...doesnt over heat at all

 

Is it RPM-dependent? Higher RPM would mean higher water pump output pressure to overcome any restrictions in the heater core.

 

agreed could be a clog or failing waterpump

 

I agree with restriction in heater core. Most likely not a water pump problem.

 

I agree with EinST, If the heater core was pluged there would be now heat at all. To check the heater core check both hoses going to the heater core at the firewall, they both should hot, if one is hot and the other is cold then you have a plugged heater core.

 

Can none of you understand EinST post. He did not say anything was wrong with the water pump. He said that if the heater core had any restriction in it when the rpm raises the water pump moves faster creating more pressure. That extra pressure now can move through the restricted heater core.

Water pumps do not fail in any way that will cause a heat problem. In very rare instances a water pump impeller can fail in such a way that they do not move enough coolant at idle,thus causing a over heating condition.

 

No body said anything about a plugged heater core. A restricted core will still flow coolant just not enough.

 

I've had a fair amount of plastic impellers have a couple fins break, hot at cruise barely warm at idle. Going off of theory it didnt make much sense but parts don't lie.