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.

Sounds more like you have air in the system. Park the truck with the front end higher or radiator higher and run it till it comes up to temperature. I have done this with the radiator cap off, but you may want to leave it on. Have the heater on "HOT" and let it run, the air will move to the radiator and end up in the overfill tank. Check your overflow tank afterwards, it should be lower.
If this doesn't work, it might be time for a new thermostat and maybe a radiator cap, if it not coming up to pressure. If the system does not come up to pressure, it won't heat or cool properly. A place like Autozone will let you rent a cap tester or may test it for you.
On the heater core issue, have you had any issues where you ran tap water through it and did not have antifreeze in the truck? Have you ever gotten rust out of the radiator? How old is the thermostat? Or did you have a leak and put stop leak in it? Stop leak will clog a heater core, since the tubes are smaller than in your radiator and reduce flow through it.
Check those things and report back your results and I'll see if I can help you. Since we are in the same state and it has been cold lately, that could be part of the problem. Now that you mention it, my heater hasn't been doing as good as it should recently. Maybe it is the low temperatures, but yours sounds like air in the system. Let us know how you make out!

Just came in from attempting to fix this. Lifted front of truck a good 2' into the air, ran with cap off, no bubbles. Air temp at outlets in cabin at 105', so some heat is making it to the heater core.

Odd thing, and now I am thinking I have a bum thermostat, is the lower radiator hose NEVER got warm. I did loosen the thermostat housing and coolant came out so I know coolant is there.

Truck is not over heating, though our temps have been in the 40's at the hottest. May attempt draining radiator and putting in new thermostat tomorrow.

I did back flush the heater core and it was clean and flowed well.

I would start with the thermostat. One other thing, is the fan clutch operating correctly? If the fan continues to run and pull air through the radiator, it will probably never heat up. Operating temps should be around 195 or so for the thermostat to open, if I remember correctly.
Once you change the thermostat, then be sure and "burp" the truck again by raising the front end of the truck. Also, with the cap off, it won't build up pressure and pressure will affect temperature. Make sure your cap is working properly before you change the thermostat.
Were you seeing any "like steam" coming from the radiator or some sign of warmth? That would be an indicator of it getting hot or not. If you have good flow, it may just be cooling off (fan pulling air through the radiator) before it gets to the lower radiator hose, but it should warm up after a while.

Bill -
I think you are on the right course. I put in a new thermostat, refilled with coolant, raised the front end and after about 20 minutes of running got a few decent size bubbles coming out and heat in the cab raised into the high 130' coming out of the vents.

The lower radiator hose was still cold so I put cardboard in front of the radiator to cut down the airflow and it is now warm, so I think you are right about the coupling. Given it is pretty cold here the next few days, I think I may remove the fan all together and see what that does for me. My commute is nearly all highway so I shouldn't run into the issue of it overheating in traffic.

I did have steam coming from the filler hole, so heat was there. I think we've ruled out the actual coolant system. So the fan will be next.

Thanks for your help.

Yer better off just blocking the grill. You still need some sort of airflow and the mechanical fan pulls in just enough even with the grill blocked... <img src="/forums/images/graemlins/wink.gif" alt="" />

I'm down here in Houston and I've had my 2/3rds of my grill blocked even during the hot summers without any problems... <img src="/forums/images/graemlins/wink.gif" alt="" />