I have a 2011 with a 5.0 and I'm having issues with cold air blowing when the heat is on. I only have this problem when the vehicle is idling. As soon as I start driving it blows warm air, but even coming to a stop at a red light it starts blowing cold air again. If I rev the engine up though, it'll blow warm. Do I have a bad thermostat? I don't much trust my local Ford dealer so I wanted someone else's thoughts. Thanks in advance!

 

Did you check the coolant level yet?

 

No, it's not your thermostat.

Check coolant as already suggested, then check water pump.

 

Thanks guys, that was indeed my problem. Glad it was something minor.

 

Low coolant? Now you need to figure out where the coolant is going! This may not be a minor issue.

 

Yeah, I know I lost some when I installed my CAI, but not that much. I'm always checking my driveway for leaks, and have never seen any. Where else could I check to see where it's going?

 

It could be consuming coolant internally. Or even heater core leaking inside the truck. Or a reservoir cap that doesn't hold pressure can cause coolant loss

 

I've had past trucks with heater core issues where they leak on the passenger side floor board. That's not the case here, and I do have pressure on the reservoir cap (I can hear it). Do I need to be concerned if it's consuming coolant internally?

 

Absolutely! You could have a blown head gasket or a cracked head.

Fill the coolant to the FULL line and keep a good eye on it.

 

I will keep an eye on it. I appreciate everyone's help!