Been a long time posting, the truck just hasn't needed much lately and if it did, the answer was on here without posting.

Did a timing belt change a few weeks ago and now have little heat. Actually, may have had little heat (I've measured as low as 90' at the vent at idle after 20 minutes if sitting still, 145' at 3000 rpm while driving). I disconnected one of the houses from the heater core (the exit one) and there was no fluid in system. I can run the truck for 20 minute (at full operating temp on the dash), remove the same hose (this is the hose nearest the drive side before the hose turns down and returns to the engine) and have all but a trickle of coolant coming out. If I hold the house slightly open and rev the engine coolant has come up (though not every time).

Sorry for the long winded backstory:
1) how do I get the air out of the line?
2) I thought this might be a clocked core, with the little coolant coming out as I rev the engine, but some does come out, does this sound like a clogged heater core?
3) Any other ideas?

Thanks. I did the timing belt job with little fan fare thanks to all the help I've gotten off this board over the years. I was looking through my old emails and found some from the original T100 list serve, that was pretty cool saw some names that are still here.