The mystery has been resolved. The heater core was fully blocked by calcium-like deposits. No water was flowing in. There is no valve on the heater hoses on this truck (97 3/4 ton). On my 96 1/2 ton Tahoe, there is a valve. The thermostat was working ok, but I changed it anyway, and there was a lot of crud on it (probably from whatever clogged the heater core). The thing that really ticks me off is that I paid a local Chevy dealer over $500 to replace the heater core less than 2 years ago. My buddy at the radiator shop can't understand how this could have happened if they really did replace the core AND flushed the system sufficiently. Don't trust those dealerships as far as I can throw them!!!/w3tcompact/icons/mad.gif
The smell of antifreeze is coming from a small split where the cooling fins of the main radiator come together with one of the side tanks. It was loosing level ever so slightly, but the crack is pretty high up on the radiator, so it only leaked steam after the level went down below that point - not a lot of volume, but pretty easy to smell. The smell was being picked up by the fresh air intake as the heater blew (cold) air into the truck. Since the radiator has plastic tanks, it cannot be brazed, so after I use up the antifreeze I have topping off the reservoir, I will probably spring for the ~$300 to replace the radiator. I'm not in the mood to do it right now since my other car (96 tahoe) just got a new intake manifold since the old one cracked where a water passage was (leaking anitfreeze like a sieve). When it rains, it pours./w3tcompact/icons/sad.gif
