99 Ranger 3.0

My heater works great as long as I am driving but when I stop a stop light or something it starts blowing cold air until I get the RPMs/Speed back up. Heater Coil? Thermostat?

The truck takes a little longer to heat up but the temp does not fluctuate when I am stopping or driving. Ideas?

 

Any thoughts?

 

water pump

 

anyway to test that theory?

 

Air bubble trapped in the top end of the engine. Get the truck parked facing uphill on a steep incline , then check the level in the radiator.
You also may have the lower radiator hose collapsing .

 

Well I have had this happen on my Exploder. Check the coolant level and then I would be looking at the coolant pressure. Also if the hoses are old they might be colapsing and restricting flow. If you are short on coolant you might want find the place that you are losing the coolant. Have fun.

 

water pump/front of engine is all wet. I am gunna go with pump failure. thanks for the help yall