not necessarily. you have to measure the temp of the water, on a hose or radiator. the waterpump housing can soak heat from the engine itself, causing the metal to become warmer than the water flowing through it, imo. hit the hose at the waterpump, for a better reading. metal will hold temps longer than water. the waterpump could be warmer, or cooler than the water flowing through it, depending on the circumstances. i'd measure water temp at the closest place i could "see" the water. (open the rad cap, and temp the water right there, for the actual temp) a hose will give a more accurate reading of the water temp, than the waterpump will, again this is imo.