You don't need the radiator fan at higher speeds because of the natural air flow. When the overheating occurs at higher speeds and not at slow speeds, a common cause is corroded cooling fins on the radiator. More heat is generated at higher speeds but that extra natural air flow is useless and irrelevant when the cooling fins are so rotten they crumble like moldy chocolate chip cookie!
One thing that will verify this is to use the heater on one of the higher fan speeds. The heater core is like a small radiator and it will dissipate a lot of the heat the radiator is unable to.
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Thursday, October 30th, 2014 AT 10:18 PM