I'm trouble shooting why my cab heater is not putting out heat. I took the heater inlet hose off the heater as shown in the photo (the hose resting on the battery). I expected to see water pumping out of this hose while the engine is running since the hose is connected just below the thermostatic housing. No water is pumping out on a cold engine. I did not wait for the thermostat to open.

Photo
https://swenracer.smugmug.com/Trucks/59-Apache/i-mBk88Jz/A

I have all new parts in the cooling system (radiator, thermostat, heater core).

Does anyone know if the heater inlet hose should always have flow from the engine or does this only work when the thermostat is open?

Even with the thermostat open and the heater hose hooked up, I don't get any cab heat.

Thanks in advance for any ideas to help figure this out.