Engine Overheating/Heater Blowing Cold Air
I have a 2002 Durango SLT 4.7L with approx. 84,000 miles. A few months ago I had a problem with the engine overheating. I took it to a repair shop, that checked it out & changed the thermostat. That solved the problem for a few months, but within the past 2 weeks I have started having problems with overheating again, mainly in stop & go traffic or city driving while at stop lights. Yesterday I had a coworker mention that my engine sounded like a jet engine. I left the engine running, opened the hood, and stood in front of the vehicle. There was a definite whine that sounded like it was coming from the front of the engine, but I couldn't isolate where in the parking lot at work. In addition, today the heater would intermittently blow only cold air. When it was blowing cold air the engine would overheat. After a few minutes with the heat & fan set on high in the defroster mode, it started blowing hot air again & the temperature gauge dropped back into the normal range. Before this incident with the cold air I thought it was the water pump, but now I'm not sure. Does anyone have any suggestions about what this could be?