# Thermostat?



## rusty baker (Feb 13, 2009)

89 Buick Riviera v-6. Drive for hours on the hiway, temp stays normal. Let it sit and idle it overheats. Drive in stop-and-go traffic and it overheats. Would you change the thermostat first and what temp would you use?


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## 47_47 (Sep 11, 2007)

I'd check the engine cooling fan first. Does it come on? For thermostats, install 190°-195°.


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## rusty baker (Feb 13, 2009)

Yes the cooling fan comes on.


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## 47_47 (Sep 11, 2007)

For the cost, I'd replace it, but don't think that's the problem. Usually, when a thermostat sticks closed the car will overheat all the time. I'd look for a restriction of the air flow over the rad, slipping belt...


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## Chemist1961 (Dec 13, 2008)

Agreed, check your belt tension. The force of air and volume at hiway speed eliminates the need for the fan itself. At low speeds the fan is not acting effectively, so satrt there:thumbsup:


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## rusty baker (Feb 13, 2009)

The car has an electric fan.


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## Scrufdog (Jul 27, 2009)

and the cooling fan is coming on while its sitting? Does it overheat while the fan is on? Do you have a way to take the temperature at the thermostat (laser thermometer or such)? Could be the gauge is off, or the fan is cutting out while it gets hot.


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## gotboost (Sep 5, 2008)

Has the cooling system been flushed,sounds like maybe a restriction in the system,so at idle the flow is slowed and gets hot,feel the radiator from top to bottom and side to side is there cold spots?if flushing is needed Pematex makes a strong flush think the part number is 811,


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## rusty baker (Feb 13, 2009)

Taking it to a mechanic tomorrow. Think the temp sender is not turning the fan on at a low enough temp.


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