My 87 6.9 radiator froze then thawed before starting. Now it over heats never did this before freeze can't find any leaks. New to dieasels but I love this truck would give up gf before truck any ideas why it is now over heating?
Sounds like your EG or PG radiator fluid is weak or is more water than glycol. You may have damaged your thermostate too. I bet its the thermostate or your loosing pressure. The radiator lid/cap needs to seal well, to maintain the water in a liquid state at elevated temperatures.