fingersix, Please pardon me. Your last sentence does not make sense. Think about it this way: If the water flow results in higher temperature at the radiator exit then that means the entire radiator is hotter. A hotter radiator will transfer more heat to the air, not less. And further, greater water flow through the engine will scrub off the boundary layer and increase heat transfer from engine to water. Greater water flow will increase cooling system capacity.
I'm not saying your pump is or is not the problem, just that "too much flow thru the radiator" is for sure not the problem.
