The Stovebolt Site Forums The Shop Area General Truck Talk It's alive....53 3100, 216

A little math quickly dispels that notion. If your coolant flows slower through your radiator dissipating heat, it also flows slower through your block and heads, gaining heat. Your engine head temp is around 400 degrees, or 220 ABOVE the ideal engine coolant operating temperature of 180 degrees. Ambient air flowing through the radiator is approximately 80-100 degrees (depending on the weather), or 80 degrees LESS than the ideal engine coolant operating temperature. 220 degree gain versus 80 loss - the slower the coolant flows, the more it will heat up.