Jim Grant's Tech Tips

'95 Ford Mustang GT, Slow Overheat

Q: I own a '95 Mustang GT and have had a cooling problem for a few months. The car will slowly overheat at a stand still. The fan will come on but sometimes it doesn't seem to cool the car enough and it will soon overheat. When I'm driving the car it actually runs too cold and never gets into the normal range. Being that it is wintertime it's not too bad but when warmer weather gets here I probably won't be able to drive the car. I have changed the thermostat, flushed and refilled the radiator and changed the belt, but to no avail. I've been racking my head for months.

- Bill K.

A: A closer inspection of the water pump and cooling fan is in order. Water pumps have impellers that can wear in a manner that reduces coolant flow at the lower engine speeds of in-town driving and stop and go traffic. At highway speed the engine drives the water pump fast enough to cover the problem. As for the cooling fan, just because it turns on doesn't mean it's doing its job. As an electric cooling fan motor wears it can lose speed/RPM. The reduced speed means less airflow over the radiator to cool the coolant. You have 2 areas to check out before the summer heat hits.