Heater not working.

[jpyjfrdmstng]

This has me really puzzled. First the problem was that the heater core was leaking. That was replaced. Then the heater didn't blow heat. Changed thermostat twice now. Engine gets up to normal no problem and regulates its heat just fine by using the engine electric fan. The heater fan blows just fine. When I turn the temperature selection knob to hot, it will blow hot air but then it slowly goes to ambient. If I turn it to cold and then back to hot after a bit, it will blow hot air and then back to ambient again. I pulled the heater hoses off the heater core in the engine bay and blew water through the heater core to check for flow, seems fine. The hoses all get pressure.

Ive heard it could have something to do with bleeding the coolant system. What is the proper way to do this?

Someone said the water pump could be going, I cant see this because my engines temperature is regulating just fine.

Is there a cabin filter on the 1995 mustang that could be clogged?

My next step is to check the heater knob rigging itself, don't really feel like pulling the dash off though!

 

[True 5.0]

Without actually looking under my to verify this, I do believe the temperature is actually controlled at the discharge point on the intake manifold. If you look at the front passenger side of the intake manifold you will see the heater line hard pipe connection. It threads into the manifold and has a plug on the back. It is possible it isn't plugged in or worse, it is broken. After all of that, I hope I'm not full of S**t.

 

[desertcox05]

ck the small hose coming off the water pump. If it has a kink in it you'll be able to get a small amount of flow then nothing.

 

[True 5.0]

ck the small hose coming off the water pump. If it has a kink in it you'll be able to get a small amount of flow then nothing.

That isn't likely the problem. The small hose is a bypass hose to promote coolant circulation through the block until the T-stat opens.