Heater Blows Cold Air When Idling.

[bcmcm]

Hi all. I have looked through the forums but couldn't find any answers. I have a 2003 Limited 4.6 V8. the heat works great running but when I am at a light the air goes cold. If i rev the engine to 1100 RPM or higher warm air again. I am thinking water pump but would like some input before I change it out. Thanks

 

[corkey]

i had the same kind of problem in my 2nd gen, it was okay , while moving, but not as warm as i thought it should be, than at idle, cold,,
i changed out the thermostat and flushed the heater core,, now,, it is the same all the time,, and the needle goes up a bit higher on the guage,, in the extreme cold, about -20 to -30 it wouldn't warm up the interior, now,, no lack of heat ,
might do the same for you too ,

 

[racin8]

check the valve in the heater hose before the firewall, that was the problem on mine.
Pictures in the thread "no heat"

 

[bcmcm]

OK stupid me. Now that I checked the level of coolant found out I needed to add almost 3 liters. Now I have hot air all the time. Yes the valve before the firewall is also sticking. I forced it open and will replace when it gets warmer outside. Thanks for your input and advice.

 

[solitary ogre]

OK stupid me. Now that I checked the level of coolant found out I needed to add almost 3 liters. Now I have hot air all the time. Yes the valve before the firewall is also sticking. I forced it open and will replace when it gets warmer outside. Thanks for your input and advice.

sounds like ya owe us all a 6 pack of Timmy's donuts. lol

 

[bcmcm]

That I do Timmies for everyone!!!

 

[Silver04XLT]

This is the same exact thing that happened to me. I had no idea what it could be and then I popped open the coolant tank and noticed it was almost bone dry.