I did a search, but couldn't find what i am looking for.
2000 Z71, 4.8L. I have no heat. The engine does get to operating temp. A few weeks ago I replaced the stat (stuck open), and refilled the system. Now, i think i have air in the heater core. When i accellerate, i hear "running water" through the core. The inlet hose to the core is hot, but the oulet is luke warm at best. I spoke to a buddy that owns a perf shop, he says that once the coolant system is opened, it must be "vacuumed" to eliminate the air in the heater core. I trust him, but surely there is an easier way! It is cold out, dammit! Am I the only one that has screwed this up?

Mucho Grassy-*** in advance!

 

I have been able to cycle the air out with several heat cycles in the past but if its being stubborn you may need to rent a vacuum tool.

 

If in is hot and out is not, you probably have a plugged core. If the blend door was stuck the out hose would be as hot as the in hose.

 

I've drained and refilled many times and have never had air pocket problems. Maybe there is an obstruction.