2006 Chevy Impala. Engine Size: V6.
Question: My Chevy Impala has a problem with the heater. The vents blow cold air when i am sitting at a stop light idle for more than a minute. Had a mechanic check the car and said the coolant was low but could not find a leak.
Thought is could be the thermostat or plugged heater core. But wouldn't a bad heater core blow cold all the time or leak on the floor? Do not see any antifreeze on the carpet and vents are hot when driving down the road. All the maintenance is up to date for the mileage, which is 55,000. What could be the problem, thanks.
Answer: Have seen this quite a bit on the V6 Impala's. Unfortunately, it's not an easy fix. You have either one or both cylinder head gaskets that are blown out. What is happening, is that you're losing the coolant in the cylinder and it's just getting burned away. That's why you see no leak on the ground. More times than not, it is the back cylinder head gasket that goes bad, but it's always a good idea to replace both when you do a big job like this. An easy way to tell if the head gasket is blown is to top off the coolant and watch for bubbles coming to the surface while the vehicle is running. That means compression from the cylinder is getting into the cooling system which causes air pockets, which in turn causes no heat. It's a pretty involved job to do yourself, unless you are very mechanically inclined. I would recommend a professional completing the repair. Always use new head bolts since they are torque-to-yield bolts. Your local GM dealer can get you all the correct parts.