Heat output is low

[PDA1]

Folks:

Our 1991 Explorer XLT (187,000 miles) heater output isn't hot enough. Yes, it's warm with a slight tendency to get "burn your hand hot" when the engine RPM is over 2,000. However, at speeds around 45 mph or less the heater output is only slightly above warm. Under heavy load, like going up a steep hill, the heater output is perfect.

I've found that the heat output is perfect after I've driven the Explorer somewhere, (like shopping) let the car sit for a while and have then driven off again.

Just for background if this might help; ambient temperature is about 40 degrees in our area during the day and about the same at night.

The temperature gauge fluctuates between the colder part of the "N" and the colder part of the "L" in the normal range.


I've already done the following;

- used Prestone's flush and fill for neglected radiators.

- back washed the heater core twice

- flushed the entire system 2 times and both times the heater was completely isolated (I cut the hoses and capped all ends) from the rest of the cooling system

-replaced the radiator (the old radiator leaked)
- replaced the thermostat with an OEM Ford thermostat (yes, the air bleeder port is at 12 o'clock)

- replaced the coolant with new anti-freeze and mixed it to achieve a -30 F mixture

I had this same problem last year. It seems that when the heater isn't used during the Summer that the problem occurs in the Fall.

Anybody have any ideas what's wrong?

 

[SportlineXLT]

Your thermostat could be bad, even though it's new....also, have you checked your water pump? Where at in PA are you?

 

[PDA1]

I solved the problem- uh, cough, cough.....it was the cold air door adjustment. (I sure did have fun working on the heater core though.)