I HAVE A 2001 FORD EXPLORER 4.0. THE PROBLEM IS I get no hot air. The raidator is full,new thermostate,blower motor works the hoses to hearter core are hot,I can hear the doors opening and closing under the dash,motor does not over heat,after running a while. I can take raidator cap off with no pressure built up and antifrezee is cool to the touch
Have you checked the thermostatic fan clutch? This is positioned between the radiator fan and water pump.
If the fan clutch is locked up, the radiator fan will spin too fast and will strip the heat from the coolant in the radiator. Sometimes there will be a roar from the engine when these fan clutches lock up. But not always.
To find out if the fan clutch is locked up, with the engine cold try spinning the fan by hand. It should rotate freely one or two revolutuions. If it doesn’t, the fan clutch is locked up and requires replacement.
Tester
You say you can hear the doors moving, but can you visually verify that they are moving to the correct position? If air is not going through the heater core you won’t get heat, even if the core is hot.
Both Tester and MC have good points. I will add that you might want to look for a possible air lock as well.
Tester,the fan only turns about half way around,I will replace it,but is that the reason why there is no pressure build up I mean I can take cap off by hand and nothing comes out no not antifreeze or steam and thats after driving it for a half hour.
I suspect a bad thermostat or one that is set way too cool. Even if new, a thermostat could still be bad. If the radiator doesn’t heat up at all, then there is a problem in the flow somewhere.
J.Meehan: How do I check for air lock?
Since the hoses to the heater core are hot, it sounds like you might have a problem with the blend door.
Take a quick look at this link