A different kind of "No heat" conundrum

[XLCOR_65]

Ok, I have searched Google and this forum and have not seen anything that closely resembles my current heat problem. I will lay out the basics:

New radiator

New thermostat (180 degrees)

New water pump

Heater core has been boiled and pressure tested

No leaves or any other obstruction in the heater box

Engine warms up normally, sticks to 180 like glue after the thermostat opens the first time. The hoses are hooked up correctly. No matter what, there is not ANY heat coming from the heater core. I just get cold air in the cab. The supply line is kinda warm and the return line to the water pump is cool. I checked for air lock and there was no problem.

Now, the heater used to work just fine. I even burned the heck out of my hand on accident one time by letting my hand rest on the heater core pipe when I was leaning over into the engine compartment...

My guess is that the new water pump is possibly the culprit. I think that it is not sucking the water through the core and back into the pump. Anyone else ever have any experience in this problem? I am going to install a new pump possibly tonight and see how it goes, but I just wanted to see what you all had to say.

Thanks!

(Hope everyone has a safe and happy Thanksgiving!)