The heat works as normal until the truck has been up to normal temps for a few minutes. When at a stop, the heat stops working and the temp rises pretty quickly. Once I start moving again, the overheating stops and temps go back to normal. Not sure if the heater works again while moving again. Haven't paid attention to that. Just noticed this in past couple of weeks, since the outside temps have gotten into the 90's.
It seems to logically be a circulation issue. What would cause the heater to work for awhile and then stop once the vehicle is thoroughly warmed up? My first instinct is the water pump is not working correctly- but there is no noise or leakage. Could it just need a flush or could it be a air bubble in the heater core (causing the gurgling?).
Stumped,
Joe