Heater cools down at low idle

2009 CHEVROLET IMPALA
36,000 MILES
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JIMMY GARDNER
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When at low idle heater cools down. When at speed or if you rev motor temperature will increase and work fine. But if you stop, like at a stop light, temperature will decrease. Could it be the thermostat?
Dec 23, 2016 at 4:05 PM
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CJ MEDEVAC
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Is Mr. Radiator full of coolant?

(my first possible issue)

Yes, a stuck/ partially stuck open stat might exhibit the same symptom.

Radiator full, If your temperature gauge pretty much stays at operating temperature with little fluctuation your thermostat is probably fine.

Is it my low on coolant guess?

The Medic
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Dec 23, 2016 at 6:04 PM
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JIMMY GARDNER
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Yep, it is full.
Dec 23, 2016 at 6:08 PM
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CJ MEDEVAC
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Ever had a new thermostat in that rig?

I believe it is a 185 degree, verify at the parts store.

Also check your heater hoses for being squashed flat/ a crimp in a bend. Replace them if they are deteriorated (as you should anyway).

The Medic
Dec 23, 2016 at 6:18 PM
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JOHNNY G.JR
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Possible air in system, might need to be bleed.
Dec 23, 2016 at 6:38 PM
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SATURNTECH9
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Are both the heater hoses going into the heater core at the firewall getting too hot to hold? if only one is then you could have a restricted heater core.
Dec 23, 2016 at 8:21 PM