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Impala Losing Heat at stop lights

I have a 2008 Chevy Impala LTZ that loses heat while at stop lights. I was interested to hear on the show somebody else having this issue. Since then I’ve spoken to other Impala owners and this seems to be common issue. There is plenty of coolant in the system. Has anybody been able to fix this by flushing the coolant system?

Do you mean the heat coming in the cabin, the temp gauge, or both?

Oops. Sorry. Heat in the cabin. The engine temperature is fine. The cabin heater blows cold air when you come to a stop no matter how long the car has been running. Especially noticeable in sub-zero temperatures.

Most newer chevy’s have vacuum actuated blend doors. Vacuum at idle is unique from other states… I’d bet that it’s something to do with the vacuum actuators or blend doors, not the cooling system.

Typical vacuum problem. Likely a split or loose vacuum hose. Since your brakes also use the vacuum, I suggest you do want to get this one fixed.

You are correct! That is the problem. My mechanic is putting in a new hose this very moment. Of course, they flushed the coolant system and replaced the thermostat first. Thanks for the help.

A little net searching suggest the problem could be air getting in the cooling system, possibly because the pressure cap on the plastic tank is not holding pressure allowing air to get into the system. The fix maybe checking the pressure cap to see if its holding pressure, replace cap if necessary, and then bleeding the air out of the system.

The latest generation Impala sadly has switched to a closed cooling system with the pressure cap on the plastic reservoir tank. I had nothing but problems with this type setup on a Ford Taurus.

Thanks! It’s worth checking-out, especially since my mechanic is still here.