daniel73

Ok, first time on here...not a mechanic in the least, either..have a 2000 F150 4x4 with the 4.6...turn the heat on after warming up the truck and it gets 'warm' but you'll never want to turn it down because you're too hot...someone said it's probably the thermostat being stuck open? Just would like to have some idea before taking it in to the shop...gauges all read normal...is it the box behind the radio that I read about earlier? Any help would be greatly appreciated.

atvrider93

could be your heater core. thermostat would keep the engine from getting up to temp

snowy

I have the similar problem with my 99 F150 4.2, when I warm up my truck and turn the heater on, it works awesome for like 5 to 10 seconds then it gets cold again...Would that be the heater core as well?.....Thanks

big cube 426

also the correct LB radiator cap.

96MiniTruck

I had the same issue with my truck. 01 w/4.6L. Changed the thermostat twice, flushed it twice, no help. Bought one of those small thermometers to stick in the vents, air would only come out at aroun 80-85 degrees. Took it to the dealership, they found the heater core mostly clogged. 1100 bucks later at my Ford dealer, now the heat comes out the vents at around 150-160 degrees.
I have also heard that it could be the blend door in the heater box. Either way, it requires removing the dash to change that too...
Good luck