What kind of shape is the rad in did you get it cleaned or boiled if it's the old one and never been cleaned could be blocked so it's not flowing properly.the pump pulls from the bottom of the rad and pushes it in from the top when you start on a cold engine as the engine warms up you should be able to put your hand on the rad and feel the rad get warm from the top down across the whole rad and slowly move down evenly across if it's cold in a section it might be cloged.
Pete
