Sooooo, the hottest coolant is coming from the thermostat housing, going back through the radiator and cooling off. The pressure is created from the pump. The pressure is the lowest going to the pump. The heater hose inlet and lower radiator hose inlet on the pump are directing the coolest coolant back to the pump. With that, I would assume, the heater control valve goes on the thermostat housing. Shutting off the hottest and more pressurized side of the system. But then, I don't run a pressurized cap on the radiator either. Sigh!!!
