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Eric
Eric, Automotive Repair Shop Manager
Category: Chevy
Satisfied Customers: 30828
Experience:  20+ yrs. experience as repair shop manager and technician.
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I have a 2007 Chevy Impala with a 100,000 miles and the heater blows warm air when the car

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I have a 2007 Chevy Impala with a 100,000 miles and the heater blows warm air when the car is moving but when you stop and its idling it blows cold air.
HI,

there are 3 common causes for this:

partially restricted heater core
air pocket in cooling system
water pump not operating efficiently


First step is to check water pump operation. Drain about 1/2 the coolant from the radiator, fill the coolant reservoir and crank engine and allow to idle for about 5 minutes. If coolant is not sucked from reservoir into the radiator and cooling system in that time, replace the water pump.

If good, then we need to flush the heater core. Disconnect both heater core hoses from heater core at the firewall and use garden hose to flush in both directions.

Reconnect the hoses and now we refill and make sure to bleed system which also ensures to get out any air pocket.

Below is proper fill and bleed procedure. I always raise the front end about 8" off the ground to do this. Air rises to the top and by raising the front end you ensure that the radiator is at the highest point in the cooling system

1. Close the radiator drain cock.
2. If a complete engine block drain was required, install the coolant drain plugs to the engine block. Refer to Draining Fluids and Oil Filter Removal for the 3.5L engine or to Draining Fluids and Oil Filter Removal.

Important: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.

3. Slowly fill the cooling system with a 50/50 coolant mixture until the coolant level is visible and stable. Refer to Capacities - Approximate Fluid.
4. Install the pressure cap loosely (threaded on about one turn).
5. Start the engine and raise the engine speed to 2500 RPM and hold it there for 40 seconds, then shut engine off.
6. Remove the pressure cap and fill the coolant system until the level is visible and stable.
7. Install the pressure cap loosely (threaded on about one turn).
8. Start the engine and raise the engine speed to 2500 RPM and hold it there for 30 seconds, then shut engine off.
9. Remove the pressure cap and fill the coolant system until the level is visible and stable.
10. Install the pressure cap loosely (threaded on about one turn).
11. Start the engine and raise the engine speed to 2500 RPM and hold it there for 20 seconds, then shut engine off.
12. Remove the pressure cap and fill the coolant system until the level is visible and stable.
13. Install the pressure cap, fully threaded on.
14. Fill the coolant recovery bottle to the indicator line, then add 400 milliliters (13.5 ounces) more.
15. Start the engine and run it above 2500 RPM until it is hot enough to open the thermostat, this will allow the trapped air to be purged from the engine.
16. Complete a series of three, 4-second-duration idles with 4-second-duration 3000 RPM cycles.
17. Turn the engine off and allow it to cool down to room temperature.
18. Fill the coolant recovery bottle to the indicator line.
19. Inspect the concentration of the engine coolant using the J 26568.
20. Rinse away any excess coolant from the engine and the engine compartment.
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