Heater not working

i need help with my 2001 ford taurus the heater. heater worked (not great) then slowly got colder each week for 4wks changed the thermostat.

First you have to make sure there’s no air trapped in the cooling system.

The heater core is highest point in the cooling system, so if there’s any air in the cooling system it’s going to collect in the heater core causing little or no heat.

If you’re sure all the air has been purged from the cooling system then the problem might be with the blend door actuator.

The blend door actuator is what controls the blend door position, and this determines the temperature of the air entering passenger cabin.


This is the air flushing procedure I use.

  1. put the front end of the vehicle safely on ramps to make sure the fill hole is the highest point in the system.

  2. fill the system until it won’t take any more.

  3. start the engine and TURN ON THE HEATER. If you don’t turn on the heater, you won’t purge the heater core. You have a valve in the system that will block the coolant from flowing through the core.

  4. add more coolant as the level drops.

  5. continue topping the system off until the system won’t take any more.

  6. fill the reservoir bottle to the “H” mark.

  7. close the fill cap and let the engine get to operating temp. shut he engine down and let it cool down. When the engine comes to temp, it’ll probably burp some air into the reservoir. If there’s no air, it’ll probably push some coolant into the bottle. That is not an indication of a problem.
    As the engine cools and the fluid within it contracts, it’ll probably draw coolant from the reservoir. That too is normal. If it does, simply refill the reservoir.

You should be done now. Check the coolant with every drive for a few days to be sure it’s staying et the proper levels.

This vehicle doesn’t utilize a heater control valve. Instead the blend door controls whether hot or cold air enters the passenger cabin.


This means the heater core always has coolant flowing thru it. So it doesn’t matter if the heater is turned on or not.


Consider me corrected. Thanks.

You have a pressurized plastic coolant tank, right? Have you been losing any coolant?

The heater core is highest point in the cooling system

Is that common w/Fords or just the Taurus? I don’t think that’s the case w/my Corolla. Isn’t the heater core is under the dash, down by the passenger’s feet?

OP, is the dash coolant temp gauge pointing to where it was when the heater worked ok?


I’ll speak from personal experience

I believe you may have a plugged heater core, due to coolant not being changed frequently enough

First things first . . . make sure your coolant level is fine

Get the engine up to operating temperature. Drive for a few miles until the upper radiator hose is hot to the touch

leave the engine idling and pop the hood

Feel both heater hoses

Both should be hot

If only one is hot, you’ve found your problem

This is by no means a Ford specific problem

The good news is that it can probably be fixed by flushing it out. All you need is a hose and a water nozzle with adjustable settings, because you force water in one end, until it comes out strong and clean from the other end

The heater core is the lowest point in the cooling system on your car. As such they tend to plug up with any rust or corrosion, as sediment will settle to the lowest point in a system. Look for the two short 90 degree bend rubber hoses at the firewall behind the engine. With the engine warm and running carefully feel the two hoses. If one is significantly colder than the other you have a plugged heater core.

I’ve heard a local mechanic say he uses a one hour CLR soak to clean out heater cores. Eric the Car Guy does too:

If you follow that path, I’d recommend that you do a pressure test on the core before reinstalling it. CLR is great stuff, but it can be aggressive to copper.

Tom and Ray commented on the show one time about chemical treatments to remove gunk from cooling system components. As I recall they said auto shops like theirs have access to chemical treatments diy’ers typically don’t. I think they said what they used was either oxalic acid or citric acid based.

Personally, I would never remove a heater core to clean it

If I’m going to remove it, it’s getting replaced

Mine too.

Heater cores today are made of aluminum.

And it says on the warning label on the back of a bottle of CLR not use it on copper OR aluminum.