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1993 Ford Aerostar Question: Why does the cooling system slowly heat up then rapidly drops down to cold ?

 

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Knuckle buster, Potwin, KS, February 09, 2014, 16:38
 Rookie

With the engine running the temp indicator slowly rises to about the o in the word normal then drops down to cold. This cycle continues throughout the entire trip. Rarely get hot enough to warm the car,

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    G. T. Service Center (4142 Answers) , Stephenville, TX - (254) 638-3236
    ProfessorG February 09, 2014, 16:46
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     Master

    Probably a bad thermostat. When it opens it stays open and not maintaining the temperature as it is supposed to do.

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    Knuckle buster, February 09, 2014, 17:01
     Rookie

    Changed the thermostat,made no difference. The warm/ cold cycle continues

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    ProfessorG, February 09, 2014, 17:16
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    Had a similar case here on RepairPal not long ago, we went back and forth believing his thermostat was new and wasn't the problem. How else will the coolant by-pass the thermostat, how do you introduce cold water to the system and by-pass the thermostat. If you purchased a lessor expensive thermostat, it might work well for every day driving in the spring and summer, but apparently it's not working to build heat. Purchase a better grade/or line of thermostat, more expensive. Later the next day he posted to me , he now has hot air and he will be able to blow dry his hair on the way to church.

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