Too many sue happy people. If the radiator was leaking when it was picked up from the shop then yes the repair shop is at fault If it had holes in it. If the neck came loose from a rotted radiator when the hose was removed then no he is not. If the oil came from a loose plug or oil filter then he is responsible. If not then he is not. Nothing like having a judge settle something like this that has no knowledge of engines but you see it all the time. Wonder why shops charge so much? Too many people want to blame a shop for things breaking on old worn out vehicles that have not been maintained. Ever think the radiator may be rotted and the pressure from a new pump may have blown the rust out. NO, just sue them for a new one!