A friend has asked me help him repair his dodge hemi. The engine is overheating when the ac is turned on. He says he spoken to an expert mechanic who says he needs a new water pump. I have explained that there is nothing to wear out in a water pump except the bearings or the seal. When water starts getting through the seal it comes out the weep hole in the bottom of the pump. Because the impeller is made out of metal, it never wears out so the pump always works even when it is leaking. The Engine has a new thermostat. But he's also told me that he regularly has to stop and put water in the radiator.
Therefore one of two things are happening. Either the leak is so bad that the radiator isn't holding enough water to satisfy the engine needs and AC needs at the same time. I believe the AC coil is integrated into the radiator core itself. Low water would quickly cause the engine to overheat. Or, the radiator is clogged up and needs to be flushed out.
He has been putting distilled water in the radiator to save money. I suggested that he stop that and start putting 100% antifreeze in the radiator. I believe antifreeze has a much higher boiling point. I might be wrong about that. In any case, as long as the water pump is turning and the belt isn't slipping, the water pump, in my opinion, is pumping water like it should and the problem is elsewhere. Am I correct? Am I missing anything?