92 22RE. Previous owner put in a rebuilt engine after 310,000k. Has two stage OEM tstat and recent flush

Since Ive had the truck, there's been no heat so with winter arriving, Im trying to figure out what's what. The situation has stumped me:
Dash gauge always reads 3/5th once warmed up (has new sender). Laser temp gauge says the head gets to 160ish F after long drive. So, not overheating, but, the cooling system has no pressure and it seems like the pump isn't working. Pump only has 10k miles on it though since the rebuild.

Wondering what to do next and curious why it's not overheating given the situation

 

Are you having to add coolant?

Usually when you pressurize the system, you can hear/see where the air/coolant/bubbles are escaping from. If not anywhere obvious, then it can be escaping through the HG into the combustion chamber. This will show white smoke out the tailpipe. Since you didn't mention this, I will assume this is no the case. However, it might not be a bad idea to do a compression test, both wet and dry, to see what is going on internally.

Water pumps are a direct drive, there either spinning or not. Usually the bearing will fail and will allow coolant to weap out. So is it leaking?

Really, it's a pretty basic system. So do some testing and see what you find.

 

as far as I am aware, the rad cap is the main control of cooling system pressure. so that would be my first guess. I'm not sure that would explain your lack of heat though cause the pump should still be pushing coolant through the system even if its not pressurized and therefore should heat your heater core. sorry i cant be more help haha.

 

You probably have air in the system and or a bad radiator cap. Park it on steep incline and top of radiator with coolant and add a new cap.

 

If you're not getting heat doesn't that suggest your t stat isn't opening and cycling the coolant through the heater core?

You can rent/borrow pressure test systems - you hook it to your radiator where the cap goes, pump it to 13PSI and see if it holds...if not, you'll hear hisses where it's leaking.

Curious to learn more too....

 

No smoke out the tailpipe, oil looks clean
Coolant level seems to be fine but Ill double check tomorrow

I had a mechanic friend check it out today and he hooked a test cap up to the radiator and with the engine running it showed 0 psi. He then put a couple psi in to the system from an air hose and I didn't hear any hissing and I think it held.
He took off the heater core inlet and there was no coolant being pumped to it

 

Have you checked that there is even a thermostat installed?

 

On the firewall is the heater core valve. Check to make sure that's opening.
Do the rad hoses get hot?

 

When I bought the truck it had no thermostat in it. I put in an OEM two stage and changed out the coolant. Hoses get to about 140-170F but not the heater core hoses which have no coolant in them

 

Sounds to me like your hoses are for some reason plumbed wrong.

coolant seeks to stay level

on a correctly plumped 22r series engine pull the hose off at the heater valve you get coolant.

I say look at the hose plumbing real close.

these engines are picky about coolant level if it is to low the heat is the first to go.