mppd20

I have run out of options, havent changed the thermostat yet, but here is the problem. Truck will warm up to 175-180 degrees and runs fine, but i get little to no heat in the cab, and the radiator cap is cold, and i can open it when truck is supposedly up to temp. top hose is warm, but does not feel like there is coolant in it. Basically no coolant circulation, looking for any suggestions.

sleepr tsi

May sound stupid, but is the radiator full? I'd let it get to temp with the cap off to make sure all the air is removed and top it off and see what happens.....As an after thought, are the heater box hoses warm?

nickg

If your only up to 170 likely (depending on thermostat rating) the thermo is still closed and NOT circulating coolant. the block can be up to temp and the thermostat still closed, that being said you could have issues with a blocked heater core or inside the heater box, the evap core can be plugged up allowing no little to no air to come out of the vents. or the blend door is not operating (no vacuum)
I suspect you need to install a cummins thermostat and go from there.