2000 F250 4x4 No Heat
with a 5.4
No Heat ?
New Radiator, New Thermostat. Heater core should be good.
No Coolant Leaks.
Everything inside the dash works.Floor,split,dash, & defrost etc.
I get about 2-3 seconds of warm air, then the air cools off.

My AC Works like a champ, when I am running my AC on MAX Cold, and turn the temp **** to warm the air.... It real does not change temp.

 

Something vacuum related sounds to me.

 

Under the hood or dash? The blend door closes, and all other vacume lines under dash are good.

 

how olds the antifreeze

 

New anti freeze... I put a new radiator in a few months back. I put in a,new thermostat on saturday the 19, the coolant in the block was bright green. Added more coolant after changing thermostat.

 

I think some have a valve in the heater hose line in the engine compartment which is run off of vacume , might want to check that and make sure if it has one that it is opening and closing properly.