Air in Cooling System
I just purchased an 02 Duramax (190,000) miles and had the engine checked because I noticed low coolant and lack of heat when idling. The Chevy dealer ran all of the usual tests (compression, die, exhaust, oil consistency, etc. ) and nothing indicated head gasket leak. However, I do seem to be getting air into the radiator system causing escape of coolant through reservoir. Also, I lose (cabin) heat when truck idles, and upper radiator hose seems to hold pressure even after truck has been sitting overnight. Otherwise, truck seems to run good. Just drove 400 miles, maintained 207 degrees engine temp, and purred along at 70 mph at about 2000 RPM. No indication of heating up. Could this be anything OTHER than a head gasket problem? Where else might air be coming from? I checked my radiator system this morning after truck was sitting out in cold all night following trip home (400 miles). The top radiator house was somewhat squeezable. It wasn't collapsible, but it wasn't rock hard either. Upon unscrewing the coolant reservoir cap and releasing some air pressure (did not seem to be a lot there) the upper radiator hose was then very easy to squeeze closed with my hand. My coolant level in my reservoir (though the truck is on a slight driveway grade) appears to be down about 2 inches below the FULL mark. I'm still not getting much heat while truck's idling in driveway (15 minutes) -- I suspect because I have air pocket in radiator system. Where might air be coming from?
2002 Chevy 2500 HD, LT Crew