hey guys,im looking at a 08 impala that doesnt have heat at idle it has a new tstate and the coolent is full i was told by my customer that two different techs told her that it was probly a vent or valve in the dash that is a common problem on these. when i raise the rpms the heat is great but at idle it is very poor.has any body heard of this and is there a best way to fix it.she told me tthey said it would cost about $300

I'm interested to see the responses you get. My parents 2009 Impala is having a similar problem..

does it have the manual control? i would look under the dash an see if you can see the actuator for temp move when you change the temp dials

Can we assume the fan setting is on high for both instances?

remember,i have heat,great heat infact. just not at idle.it acts like there is low coolent ,so to the first response you should check your 09 coolent levle an possibly replace your tstat it might be stuck open. what i need to know is about this vent or valve that is located in the dash,i am not talking about the acuator when that gos you loose heat completely on one side while still haveing heat on the other side(at least thats the way it is on the 04)...dual climate control!does anybody have access to a exploded veiw of the system?

https://www.gmforum.com/lounge-99/gm...tabase-304633/

Initial tests like pressure on rad cap and pressure test rad/system and finally the water pump test.
I am not sure if there is an air bleed valve on that car, but getting air out of system is needed after replacing the thermostat, and try a new rad cap.

What is the water pump test the rest all check out

Water Pump test is:
Release belt from around water pump pulley. Ensure it spins freely and pulley up/down movement is tight, indicating a good bearing. Ensure the water pump is not leaking or weeping anywhere. I would run my finger around it too to check for wetness & use an inspection mirror for any potential leaks.

You should remove the radiator cap, start, and run the car until it reaches operating temperature, have someone hold the gas pedal down (your vehicle is a drive by wire, since there is no throttle cable) have your rpms up to approx. 2200 with the cap removed, watch the coolant reservoir for air bubbles, once you see them replace the cap, after topping off the reservoir. if this does not work, You have a leak somewhere.