lol ^^ not quite. its a bit more scientific than that. water under pressure has a higher static boiling point. the higher the pressure, the higher the boiling point. thermal transfer depends on the differential between the surface producing the heat, and the surface taking the heat. so in theory, the higher temp in the rad fluid has a greater differential temperature than the air flowing through the rad. resulting in better cooling. sounds fancy eh? reality is, unless you rape your car around a track, youll never get the coolant hot enough to release the stock cap. if you are, then theres something wrong with your car.