No MX, the pump only circulates the water around this closed system. The pressure comes from the water being heated up, and expanding. Excess water ends up in the header tank. Max pressure is reached just after turning off the engine. Since the block is still very hot, and there is no cooling by the radiator, then for a few minutes at least the temperature/pressure may rise. That will be max pressure and that is the time to look for any external leaks. Anyway, make sure your friend puts the recommended coolant into the system and not plain water.