A fluid pump assembly comprises a pump housing and a fluid pump disposed within the pump housing. The fluid pump has axially opposite first and second side faces and includes cooperating impeller and rotor members. The fluid pump assembly further comprises inlet and outlet ports disposed adjacent to the first side face, a pressure chamber formed within the pump housing adjacent to the second side face, and an end plate disposed within the pressure chamber and movable relative to the pump between a first position and a second position. The end plate has axially opposite inner and outer end surfaces oriented so that the inner end surface faces the fluid pump, while the outer end surface faces away from the pump. An area of the outer end surface of the end plate is greater than the area of the inner end surface thereof.