pressure test the coolant system while it is cold then while it is warm. Be careful popping the cap when its hot/warm I only refill coolant systems with a burper funnel or park the truck on an incline over 15 degrees and fill it up/let it warm up and top off. You might have a blown hg or cracked head.... why the new radiator? just a leaky one or did it totally go out and engine overheated?