1988 7745 coolant problems

Hello again,
I'm having a coolant flow problem on the tractor. The bottom rad hose stays cool to the touch after it's up to temp. Top of rad, manifold to heads and heater loop are all hot. New pump, new thermostat, new head gaskets and new rad cap but it still appears to not flow. Just removed the pump and it still looks brand new (it is) and spins the impeller freely. Flushed rad and it flows freely as well. Pretty stumped on this one. New pump was from a zetor dealer, but a dud?
Any advice?
Thank you

Maybe it's a sluggish thermostat?

Your cooling system is working perfectly correctly! cold bottom hose is normal under light load

I was thinking maybe it is. The temp gauge comes up to the beginning of the green, but the rad cap can be removed with no pressure build up and I can't really see any fluid movement in the rad while running?