No heat at startup

[Shelby Sport Trac]

No heat. Replaced the thermostat. I have heat now. But only when I’m moving. Heat doesn’t warm up enough to thaw the windshield at startup. Did I miss something?

 

[Todd Z]

Blead / Burp the air properly ??
Is the level 100% full.
Check the heater control valve function.
Could be the Check valve in the vaccume line on top of the computer under the hood.

 

[Shelby Sport Trac]

Thanks for the info. It all started from a leaky transmission line on the bottom of the radiator. Heat didn’t work after that. Had a new thermostat installed. It was low on coolant. Topped it off. No heat at idle.

 

[user 78012]

Pull the vacuum line to the heater core control valve and see if it changes.

I haven’t had mine hooked up for years. Having stagnate coolant sitting in the core just seems like a bad idea.