Another cold heater problem
I've searched and read numerous threads, but all of the information I've found hasn't solved my problem.
I have a 91 Fox body coupe and my heater blows cold air. So far I have checked everything I can think of.
The vacuum lines are intact and I can change from defrost to vent to floor.
The mix door cable is attached and moving, and I believe the door itself is moving because I can hear it and when I put the temperature control all the way to hot there is a slight decrease in the amount of air blowing from the vents. I assume this is because the heater core airflow path is smaller than the A/C condenser path.
The hoses on the heater core both get hot. The inlet hose does have the flow restrictor in place. I flushed the heater core earlier today by removing the hoses and sticking a garden hose in it. It flowed really well from the start, and brown, rusty water came out for just a few seconds before the water went clear. I flushed the core in both directions, backwards first, then the other way, then backwards again.
When the car gets up to normal operating temp., I get cold air no matter what I do. If I turn off the heat for a while (about 10 minutes or more), hot air will blow from the vents at first, but the temperature rapidly decreases until it is cold again.
Thinking I had air in the system, I tried driving with the radiator cap loose in an attempt to burp the system, but I still get cold air from the vents.
I'm resigned to the fact that I may have to do the dreaded heater core swap, but I'm hoping someone may have some advice on something I may have missed. Is there an easier/better way to purge the system of air? Could the flow restrictor in the inlet hose be clogged?
Any help would be greatly appreciated. Thanks in advance.
355 cid, Bennet ported Canfields and Vic Jr., 750 BG carb, full tubular front suspension with coilovers, UPR fully adjustable rear suspension, Aerospace 4 wheel disc brakes, chromoly cage