heat / water pump question

I recently replaced the head on my 86 xj, 2.5L 4 banger. Now I have no or mimimal heat, where I used to be able to toast marshmellows with my heater before the head change. I thought that maybe the new thermostat I put in was stuck open, so tonite I changed it. Still no heat. I had the radiator cap off, and could not see the water moving, as I figured it should when it reached temp and the thermostat opened and the water pump was pumping the water around. So I am thinking maybe bad water pump, although I changed it about a year ago, and it does not overheat. It idled for about an hour tonite, in a nice warm garage, and didnt overheat, but no heat either. I even changed out the coolant temp sensor with one I had from another engine, just to see if maybe it was getting hot and the sensor was bad. I know the idiot lite works too. All the little vacuum motors work on the heater system, and the lines going to the heater core are very warm (not hot, but better than luke warm). Now for the main thing.... where do i go from here ? change the water pump ? flush the heater core ? I plan on swapping the engine in a few weeks (maybe longer) but will be keeping same head and intake , just putting my rebuilt head on another block, but dont want to freeze in the mean time

It sounds to me that there is a lot of air still in the system in the heater core, or perhaps the heater core is now partially plugged with junk. If its been over a year, now is a good time to do a cooling system flush and fill. Lots and lots of post via search on cooling system flush and fill. The main idea is to continue to reverse flush the system until the core and all other components are running nice clear water. Your Haynes / Chilton manual should have the procedure.

In addition to the reverse flush procedure, take your thermostat off and do what 5-90 recommends and drill a small 1/16 inch hole at the 12 and 6 positions on the thermostat. The idea is to allow air to escape through the upper hole while allowing fluid to take up the now evacuated space via the lower hole. Button everything back up and fill the system. Make sure that you check it for the next few days to top it off and you should be good to go.


Dave

There is a vacuum operated water shutoff valve going to the heater core, bypass that and see if you don't get heat.

no more heater water shut-off valve, previous owner took it off, guess I will have to try and flush the gunk out of the heater core, hopefully it will work.
I have a little warm air coming from heater, but as soon as I put the blower fan in high, it cools off the heater core, and then I get cool air coming out

just got a chance to check today, the upper radiator hose is very warm, the lower isn't. Still very minimal heat, not overheating though. Thought I would flush the heater core and put the other water pump I have in this weekend.