Chevy cooling system issue

[KrazyKevin]

I know this should go in the 99+ forum, but we are in a bind for answers. My buddy has a 04 5.3L chevy silv. He's having odd cooling system issues. It started out with his heater blowing cold, but truck was running normal temps. He found a gasket leak behind the water pump, replaced gasket, thermostat, hoses, and put on a new pump. Now, the truck will blow warm for a little while, then go cold again. Plus, the truck now overheats. He's tried degassing it and says he thinks it is clear of air pockets. With the heater off, the engine will get to temp and start burping water out the overflow on the water jug. If he turns on the heater wide open, the truck will run at normal temp. He blew through the heater core, its clean. So, we think we got it narrowed down to a plugged radiator, air pockets, or headgasket. The only reason we leave headgasket in there is because he thinks he got all the air out and it keeps burping air and water out the jug.

Sorry for putting this in this forum, but there wasn't a lot of activity in the other forum.

PS. He does own a orange 72' though

[KB71C10BBSUPER]

Sounds as if you have a defective Tstat. But as you are running you could have a Radiator hse colapsing. Check your Radiator for Blockage also.
Goodluck

[usmcchevy]

Try removing the upper hose from the rad and dumping coolant in. That should take care of any air pockets.