01 F-150 no heat at idle

[jgerber]

01 5.4 gas no heat at idle, upper hose hot, lower hose cold, does have the oil cooler in the lower hose. Replaced t-stat and water pump. Both heater hoses get hot????

 

[Storm]

Check the heater blower and valve.. Is it blowing but not hot? Could be a valve.. There should be a valve towards the front of the engine from the Heater box. it opens to allow the hot coolant to flow through the heater element and shuts for AC operation. It's vacuum actuated..

 

[blacksnapon]

By all means check blend door operation, and water control valve operation. Storm was right about it being there for a/c operation. If Its been known to have previous leaks, excessive use of stop leak products can plug up the heater core, with those same symptoms.

 

[d-kuzmen]

Also check to make sure there's no pens or pencils stuck in the blend door, seen that happen a few times.