2008 Chevy Impala, was in a front end collision, the heater only blows hot air when the rpms are above idle. when at idle it blows cold. Any ideas?

You need to fix the coolant leak, then refill and bleed cooling system, then you will get heat and cure overheating problem too

2001 Chevy Tahoe Heat Problem - Tahoe Forum

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Dec 5, 2008 - 10 posts - ‎7 authors 2001 Tahoe, the front heater blows a little hot air when the car warms up and then blows cold air. The rear heat seems to work fine. I changed ...

Rear AC blows hot air - Tahoe Forum - Chevy Tahoe Forum

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Jul 14, 2008 - 10 posts - ‎5 authors
On my wifes 03' Yukon the rear air conditioning blows hot air no .... Pull the panel off and look at the hot/cold actuator shown in the picture.

providing your coolant is full cause low coolant will cause no heat
and your temp gauge is normal in the middle then most likely u have a bad blend door actuator usually on the passenger side

Hi Chris, sounds like your thermostat may be worn and not closing all the way which would cause your engine to run cool at times. If you have a temp gage it should tell you if the engine is actually warming up or not. If not I would replace the thermostat.

go to www. aa1car.com and get the topic and fix it. However you can see the diagram attached.
God bless you

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

That sounds like the coolant level is low. If it is not the use of "stop leak" has probably caused a partial clog which restricts the flow of water unless the vehicle is turning higher RPMS. While sitting still raise the RPMS to about 2000 and see if the heater blows hot air to see if the above mentioned problems are fact.

CK FOR VAC LEAKING TO TEMP BLEND DOOR

Impalas are known for this issue, where the heating won't work properly.... usually caused by trapped air/bubbles in cooling system or slightly low coolant level. Park car so that the right front side is elevated and remove the coolant OVERFLOW bottle cap (NEVER the radiator cap) while engine is running.. This should allow the trapped air to escape. Also add a bit more coolant if needed.

1 Inspect Cooling System Mix Coolant level low or flow is restricted. 2 Inspect Thermostat Thermostat stuck closed 3 Inspect Heater Control Valve Leaking or defective heater control valve. here something to help u

Here to help Shaun