Nope. For many years radiators have been so efficient that often they cool just fine while the car is standing still and the electric fan doesn't even turn on.
The most common thermostats regulate near 195 degrees but coolant CAN get up to 220 degrees under some driving conditions. The water in the coolant boils at 212 degrees but for every pound of pressure on the system, the boiling point of water goes up three degrees. That means the water won't boil until 257 degrees with a common 15 pound radiator cap. If the temperature is over 212 degrees, the water will boil once the cap is removed and there's no longer any pressure in the system. THAT'S why we remove hot radiator caps slowly, ... To see if the water is going to turn into steam.
Even when an engine overheats, the coolant temperature drops below 212 degrees within a few minutes after stopping the engine, then the radiator cap can be safely removed. Sometimes the coolant will boil shortly after the cap is removed when the engine is very hot because the heat from the engine is migrating into the coolant and raising its temperature but that heat is not being taken to the radiator to be given off to the air.
Tuesday, May 8th, 2012 AT 8:09 AM