I drive a 97 ford expedition and the heater only blows out cold air. it is not the heater core. what else could it be?

heater hoses clogged up, check where heater hoses connect to engine for clogs. Rust and corrosion love to build up in these locations.

No hot air is due to low coolant, or even poor coolant flow. The engine heats up the coolant, and it passed through your heater core, and the heater blower motor pushes air through the heater core to warm up the air. If your "fan"is working, but the air is cold, make sure your coolant level is good.

Your heater core is leaking, needs to be replaced asap... see if there any leak around the passenger compartment area, that is where the heater core is usually located. Other then that, could be leaking coolant into the engine because head gasket is leaked, but and only if you see lot of whitish smoke coming out of your tailpipe, but in this case, looks like you have a leaking heater core.

two things that I have seen cause that problem is the blend door get stuck or stop working and the Heater Control Valve go bad and stop the hot coolent from going to the heater core. I hope this info helps

an expedition has a heater control valve, being from california the heat rarely got turned on so the coolant just sat in the core, expeditions are prone to plugging up heater cores anyway and this would be my guess as to what has happened. the fix would be to remove both hoses from the core and attach a garden hose to the core itself, see if the core will flow water in both directions, if it will, run water in both directions until it runs clear, if not replace the core, also make sure the control valve is not stuck and that the vacuum lines going to it are routed properly, finally.... make sure to completely bleed the cooling system so that there is no air trapped in the system, especially in the heater core

its the blend door behind the glove box. I had the same problem

check your coolant level in the radiator if it's low it will not fill the heater core

I ASSUME THIS IS A 98, THIS PROBLEM IS CAUSED BY A PART CALLED AN "AIR TEMPERATURE CONTROL BLEND DOOR ACTUATOR MOTOR" THIS MOVES A DOOR BETWEEN THE COLD AIR FROM THE AC AND THE HOT AIR FROM THE HEATER CORE, YOU WILL NEED TO REPLACE THAT ACTUATOR. .

Make sure the heater core is in the open position by using the shut off valve and turning it to open. next, you may have a malfunction in the direction door the directs the air flow in the dash. a lever may have become lose or separated. may be a bad servo motor not directing the door to move to the heater position. i would start by checking that shut off valve first on the heater core.

impeller is made of plastic on teh water pump and its slipping and spinning on the shaft renew before weather warms up as engine will overheat