OK Jim I'll try to defend this a bit, this is a standard rad with a temperature sensor in the bottom, (Fiat 127) fine aluminium finned, copper tubes. By making sure the temperature of the water returning to the engine is reasonably cool you are providing a temperature gradient to allow the engine to cool. If you are worried about overcooling, (not much fear in a Hood I think) water flow will be controlled by the thermostat anyway, which is sensing the temperature of the water coming from the engine. I had a problem with a different car where the sensor was high up in the system and when the coolant level dropped due to it boiling, the sensor no longer thought that it was hot!
Peter