My 1987 ford mercury monarch sustained a broken heater hose, was towed into the garage and repaired. The mechanic ran the engine at idle for over an hour and declared it repaired and fit to drive. I drove the car about three miles, the engine light came on, the car overheated. I was towed back to the garage coolant was added again, no leaks were seen, the coolant was circulating, the engine was run for an hour, hose temp were 170 degrees and the car was test driven. Again I left the garage and again after 3 miles the car over heated and had to be re-towed to the garage. Can you give any help or explanation? The mechanic can't explain.
Thanks for you help.
It could be a few things... The waterpump could be bad, even if the water is circulating at idle. The impeller could be loose on the shaft, and at higher engine speeds will not spin, thus causing your overheating since no water is being circulated. It could also be the belt, clogged radiator or extremely lean running condition, but my bet is on the waterpump.