Ok, here is alittle background on the issue. About a week ago my wife was in the city in stop and go traffic and her coolant light came on. I had her shut the car off immediately and she said the engine temperature was hotter than normal. I had her wait until it cooled down and the coolant was alittle low, so I had her add some water/coolant. She was close to the highway, which she took all the way home and the temperature was fine. We drove it for a few days, all highway, and the temperature was fine for the whole time, including some longer trips. On sunday, I let the car idle in a parking lot and it immediately began to heat up and the coolant light started blinking. I let it cool down, and checked the coolant in the resevoir and it was still very hot, so it was circulating. The fan never kicked on while the vehicle was idling.

I took the car to "my" mechanic and he says its the water pump. I cant understand how the vehicle wouldnt overheat while driving if the waterpump was bad. It seems to me that it has to be something with the fan or a sensor.

Please reply back so I have something to discuss with my mechanic.

 

Most likely a water pump starting to go. At highway speed and revs you are getting enough pump force and airflow to keep things cool. In traffic and low revs the pump isnt pushing enough flow to keep things cool.

Model? Engine? Mileage? Last time t-belt and waterpump were replaced would help us help you.

My guess is the waterpump is not stock and was replaced with a plastic finned waterpump that is starting to fall apart.

Also, if the coolant got low that means it went somewhere which means you could have air in the system. Do a search for burping the system and make sure the air is out of it. That can also cause your symptoms.