overheating

2006 HYUNDAI SONATA
210,000 MILES • 3.3L • 6 CYL • FWD • AUTOMATIC
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MITZI GIBBS-HARTMAN
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after driving the car for a while the temperature gauge needle starts climbing all the way up to high. if I am going down the freeway it cools it back down but when I start going very slow in the neighborhood it is back up.
a compression check was done and the pressure is fine. Does not always heat up though, sometimes I can go all night long without it heating up at all. we are changing out the thermostat now to see if that happens to be the problem.
May 10, 2017 at 6:16 PM
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CARADIODOC
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You are overlooking the most important clue. Vehicle speed is a factor, and that rules out the thermostat. The most likely suspect is a bad radiator fan motor. That is not needed at highway speed when natural air flow is sufficient. The fan is only needed at low speeds, so if it is not working, that is when the overheating will occur.
May 10, 2017 at 10:15 PM
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STEVE W.
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Think Doc has it pegged. A bad fan or fan controller will give the exact issue you have.
May 11, 2017 at 6:09 AM
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MITZI GIBBS-HARTMAN
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Except that the fan was checked and it works like it's suppose to. Couldn't the thermostat stick at times?
May 12, 2017 at 9:29 AM
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STEVE W.
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Not normally. They either work or the fail, no real middle ground where they stick. Could be a bad water pump with a slipping impeller or you have a failing hose or radiator.
May 12, 2017 at 7:07 PM