I have a 2001 f150. My air only blows hot when there are some rpm's put on the engine. I have done pressure tests, put all new antifreeze in the system and cleaned out the heater core system. Shop is telling me I need a new heater core but several experienced mechanics said it sounds like I need a bigger thermostat. Is my heater core bad even though I have no problems with overheating? My temperature never climbs or falls.

 

It sounds like you could have thermostat with too high of a temperature, or no thermostat. If the temp is too high, it will not cycle closed as oftern to allow the temperature to build up. Same/similar result if there is no thermostat.

Perhaps some others will have more suggestions.
Good luck.

 

Isn't a thermostat easier and cheaper to install than a heater core?

 

Way easier...but your heater core may be clogged...when you changed your anti freeze...did you do a flush with some radiator flush with the Heat on prior to refilling ?? You heater core has nothing to do with your engine cooling...but it does use the engine anti freeze for heat...your T-Stat should be a 180-190.

 

I am not sure. I took it to a shop and had the flush, pressure tests for leaks , and the heater core system cleanedbut of course they wanted $700 plus cause they think the heater core is bad. Outside mechanics that r not trying to get $700 out of me thinks I need to put in a 190 t-stat.

 

Go for the t-stat, it's cheaper and if it doesn't fix the problem, it's still not a bad idea to have a new one.

 

I was just wondering cause I have always heard that if you core is out your engine will get hot and drip antifreeze in cab.

 

So r you saying an r190 t-stat would not help?

 

You'd smell it if it was leaking. Wife had a Beretta that wouldn't put an ounce of heat into the car. Changed the thermostat and worked great

 

Thanks everyone for the info. I will change thermostat asap. If I go to a 190 it won't mess with my a.c. Will it. Cause it works fine now. My heater air just don't get very hot until I run some rpm's on the engine.