This is usually not needed. Only do it if the engine is not running well. A weeping water pump is an indication of an impending failure. Have it replaced. Note that this should also involve a drain and refill of the engine coolant which is normally replaced at 100k miles and every 50k miles thereafter (along with the inverter coolant, use only Toyota Super Long Life - SSL coolant in both loops). JeffD
Do you have service done at Thomas toyota? Have you had your prius serviced there before? How are they in the service department?