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OT - Question for all you mechanics

Joe Shmoe

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Thermostat could be sticking also,son in laws jeep overheated and boiled over,put water in it and it don't leak a drop. But when he drives it temp guage goes up to almost hot then drops and repeats that cycle. But if it sticks just a little to long it will boil over.

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You bet it does. In approximately 1990 I towed a small trailer that held the bare frame and components that went into making the car in my avatar behind a Chevy Cavalier from Hagerstown, MD to Birmingham, MI. While climbing the hills on the PA Turnpike we would watch the temperature gauge climb, whereupon we would turn off the AC, roll down the windows (It was July) and crank the heater to full. With the vents aimed to blow the hot air out the windows, we watched the temp gauge drop immediately. Without that trick I would have cooked that tiny 4 banger.

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In the old days there was a belt driven fan behind the radiator. A slipping belt or broken belt could cause loss of airflow through the radiator.

Now many / most have fans driven by electric motors. The motor turns on via a thermostatic switch which senses coolant temperature. There is still a mechanically operated thermostat which regulates flow of coolant through the radiator.

I believe the electic fan is necessary on cars which have the engines turned sideways. It is tough to rig up a belt. It may also be good for fuel consumption. Even with some clever mechnanism to allow slip of the fan, it was always taking a few horsepower.

The bottom line is that the fan motor or the fan thermostat can cause problems.

BTW, the electric fan typically does not have to run when the car is moving at road speeds. There is sufficient airflow through the radiator without it. Yo may hear it turn on when you stop at a light.


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