I have a '90 F150 w/351 and am having trouble getting heat. Truck runs about at N on Normal (not sure what that is in temp) with a 195 thermostat. When I start the truck I can usually hear something like the heater core filling up with water (sometimes same sound when I accelerate quickly). the air coming out is barely lukewarm with the temp **** all the way over to Warm. what can I do to get some hot air coming out?!

 

A.) Make sure your coolant overflow reservoir is filled to recommended level. Even if you pop the radiator cap and see coolant, if the reservoir is empty, you will pull air back into the radiator and this may be what you are hearing. (Generally, if you induce air into the cooling system the temp gauge needle moves up and down quickly, rather than staying at a steady reading.)

B.) The heater core may be partially plugged. Try disconnecting the heater hoses and back flushing the core. (See above posting on "I Cant Believe This Worked")

C.) If you have adequate heat on VENT or DEFROST settings, the air diversion door may be out of adjustment.

 

The air diversion door is okay. I took the core out and flushed it both ways and only got a little bit of stuff out (not enough to look like it would cause a problem). Should I replace the core? Does it matter which heater hose hooks up to which port on the core?

 

Ford manual indicates the hoses should not be replaced backwards. If you still have no heat after flushing, with the engine at normal operating temperature and heat setting selected, feel both hoses at the point where they enter and exit the heater box. Both should be about the same temperature, hot to the touch. If the exit temp is noticeably cooler, then the core is plugged. If both hoses are equally hot, then the problem in internal, within the heater assembly. You may want to check the temperature selector cable to see that it moves the temp blend door at the heater assembly.

 

myne dont make the noises but i have no heat at all my heater hoses dont even get hot. so im just assuming on myne the heater core is plugged. anyone had this before or have any advise?