Another Heat problem

[fiction1990]

2003 xlt with rear air. I have read through the forums and think I have tried all the suggestions. I have flushed the sytem and both cores (had good flow) I have changed the thermostat, the heat valve by the valve cover, fixed the blend door motor and I'm pretty sure the door for fresh air works. The problem I have had and still have is that it takes for ever to heat up. I can remote start it and after 18 minutes when the the timer runs out I dont have heat or at least very little heat (not enough to even defrost the windshield).
If I go up on the highway it will get nice and warm until you come to a stop light and then it cools off again (not cold but a signifigant difference in warmth).

Please any ideas on what to change or look for?

 

[fiction1990]

Is it possible that the water pump just isn't working properly and not flowing enough when at idle?

 

[FordFool2]

Almost sounds like a vacuum problem. There is a 3 way valve on the passenger side heater hose to allow flow of water to the heater core. That valve is vacuum actuated. When you are idling or sitting at traffic light the engine vacuum is at it's lowest. On the highway with engine rev'd up, lots of vacuum. Check the valve, the vacuum connection and listen for possible vacuum leaks under the hood and down near the passenger firewall where the vacuum hoses connect to the controller.

 

[fiction1990]

Thanks I will take a look at that this weekend. I have another question, is there anyway to recirculate the air without putting it on max a/c which turns on the a/c?

 

[3866]

Max vacuum at idle.