[petrock]

Pop the cap and see if there is flow. There is a possibility you have an air lock between your thermostat which would restrict any flow.

DO NOT DO THIS WHEN THE TRUCK IS WARM/HOT!!!! Coolant only flows when the thermostat is open. The thermostat only opens when the coolant is hot and under pressure. If you pop the radiator cap in this state you'll gush extremely hot coolant all over the place and potentially injure/burn yourself.

If you haven't already, I'd get the factory service manual for your year/model ride and follow the correct procedure for burping the cooling system.