I have a 2000 Ford Expedition with about 108,000 miles. The truck runs very well but suddenly yesterday I realized the heater was blowing cool air when I had the heat on. I suspect the thermostat and that is something I could probably fix myself. Being on a fixed income it may be very expensive for me to go to a dealership or even the corner auto-repair shop. Could it be something other than the thermostat?
Hello, find the hoses that leads to the heater and see if they get hot as the car warms up. If they are getting hot you problem is within the air circulation system - a blender door perhaps. Do you see the temp gauge going up when the car is running ? Please post you results.
Have you checked if you have enough antifreeze in the radiator ?
Hi Cast Iron, thanks for the reply. The temp gauge stays right in the middle where it always is and I don’t know what a blender door is?
I am not very handy when it comes to repairs but I think I can follow your instructions. I’m a bit disabled so it will be awhile before I get out to the garage but I will get to it today and let you know how I made out. Thanks again, Dave.
By the way, if the hoses remain cold does that mean it is the thermostat?
Before checking for a bad thermostat or a defective blend door, make sure there’s no air trapped in the cooling system.
To do this, get the engine up to operating temperature, With the engine idling, slightly loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip this between the upper radiator hose and the radiator hose neck. Allow the engine to idle until all that comes out the radiator hose is coolant. Remove the screwdriver and retighten the hose clamp.
Thanks Tester but I’m not risking a hose blowing off and me getting scalded. I would leave that to the professionals.
with some exceptions, the heater and hoses act as a bypass for the thermostat, so the water pump will send the coolant to the heater and back into the engine till it opens (reaches an preset temperature, each thermostat has one) and recirculates towards the radiator.
I had a 1984 Oldsmobile that had a heater control valve on the heater hose controlled by a cable on the dash and a bypass hose from the water pump to the block, so when you move the temperature dial inside more or less cooling pass through the heater so no blender door was needed. Interesting design, to say the least.
Inside the air circulation box, the blower sucks the air from outside or inside intake and routes the air through the heater core or a/c evaporator so you can control the temperature in the cabin, this is achieved by means of a blender door controlled by vacuum or an electrical motor.
I did not like that the hoses are cold, it means that you have a problem in 3 areas: the heater core is clogged, the is not enough coolant in the system or the water pump impeller is faulty. I am having problems with your temp gauge at middle way, but I’ve found it to misleading sometimes. I need you to let it coll down, then run the truck again. Attached to this reply you will find a step by step troubleshooting procedure. Please follow it and post your results.