Ahh I'm a dumby. If the water pump impeller is far enough gone as is common on old stock units, it will provide zero flow or equivalent. Old unchanged coolant from past owners easily leads to a dead pump.

 

If the water pump was trashed, the heater would not "work great". The log jam has to be in the thermostat housing.

 

+1

 

Unless maybe it's just pulling enough coolant through to the pump from the heater core to get heat? I don't know lol. I say screw it replace ALL cooling system components lmao. That's what I did on my 91 all at once. Fixed my overheating (granted everything was in poor condition from the PO and my water pump was making the dead bearing whistle sound).

 

Try pulling that water pump off had the same problem changed everything and overlooked the pump there were no fins left on it id give it a shot

 

Ok, everyone the results are: (drum beat)

Inaccurate coolant temperature sensor unit at the back of the head.

The radiator hose wasn't getting hot because I shut the car down before it could, thinking I was about to overheat.

I broke my original sensor off while tightening it in the new engine (that was a real pain to get out!) So I bought a new one from my local NAPA and they only had the cheap sensor in stock that day.

Just another lesson to buy quality parts!

Thanks for suggestions everyone.