Ok this is my first post here. Anyway thermostat is new. Had blockage in heater hoses, I cleared all the hose and the heater core is flowing. I let it run for a while with cap off to get any air bubbles out Truck seems to run at normal temp. my next guess would be water pump. But wouldn't there be other symptoms? Thanks

 

Could a bad rad. cap make the heat not work and motor not warm up all the way? gauge only goes up about 1/3 of the way. I bled the crap out of the system with front elevated so no air pockets

 

A bad Tstat (stuck open) will not allow the engine to get up to operating temperature. That is the first place I would look.

 

I figured it out. Had another clog where it goes to the auxiliary idle. Good to go now