I usually just fill up the res. with coolant till the full mark while the coolant is cold, start the truck with the cap on the res. off, keep putting more coolant in while truck is running to keep it above the minimum line (to not get any air in the system), I do this till my vehicle has been up to temperature for about 10 minutes or so, reving it a little here and there with the heat on in the truck, then drive it around a little and then check it again. That usually is the ticket for me!!