Mystery overheating

[twobjshelbys]

I had overheating problems with my Cobra. It was also at low speeds. After much gnashing of teeth and adding an overflow tank I probably didn't need, it still overheated. It ran at correct temp at faster speeds, but occasionally would run hotter than normal. My mechanic friend and I tried everything we could think and then his smart a** son pulled the water pump and found that the "fan" part of the pump that was just pressed on to the pulley had lost is press on. The overheating happened when the fan would happen to lodge in the "closed" position and cover the thermostat return. If it landed "open" there was enough convection and the size of the radiator to more than handle normal street driving. Note that all of the open tank etc. tests showed the system flowing, but in the end, not enough.