A pressure and thermostatic relief valve comprising: a pressure relief valve housing having a passage for selectively providing flow communication between a pump housing discharge side and a pump housing suction side; a pressure relief actuator positioned at least partially within the passage and movable between a closed position preventing flow communication between the discharge side and the suction side and an open position allowing flow communication between the discharge side and the suction side; and a pressure relief spring for biasing the pressure relief actuator in the closed position until a pressure difference between the discharge side and the suction side exceeds a predetermined amount; wherein the pressure relief actuator further includes a thermostatic relief valve, the thermostatic relief valve comprising a thermostatic relief valve shell having an elongate inner bore, a first opening in communication with the pump housing discharge side and a second opening in communication with the pump housing suction side; a wax thermostatic element disposed within the shell bore; a thermostatic actuator piston movably disposed within the shell bore adjacent the thermostatic element so that expansion of the wax thermostatic element under elevated temperature conditions moves the thermostatic actuator piston from a first position to a second position; a poppet movable between a closed position and an open position and disposed within the shell bore adjacent the thermostatic actuator piston so that movement of the thermostatic actuator piston from the first position to the second position causes the poppet to move from the closed position to the open position, wherein the poppet prevents fluid flow between the first and second shell openings in the closed position and the poppet permits fluid flow between the first and second shell openings in the open position; and a thermostatic actuator return spring disposed within the shell bore and biased against at least a portion of the thermostatic actuator piston for returning the thermostatic actuator piston from the second position to the first position; characterized in that a poppet return spring is disposed within the shell bore and biased against the poppet for returning the poppet from the open position to the closed position. a pressure relief valve housing having a passage for selectively providing flow communication between a pump housing discharge side and a pump housing suction side; a pressure relief actuator positioned at least partially within the passage and movable between a closed position preventing flow communication between the discharge side and the suction side and an open position allowing flow communication between the discharge side and the suction side; and a pressure relief spring for biasing the pressure relief actuator in the closed position until a pressure difference between the discharge side and the suction side exceeds a predetermined amount; wherein the pressure relief actuator further includes a thermostatic relief valve, the thermostatic relief valve comprising a thermostatic relief valve shell having an elongate inner bore, a first opening in communication with the pump housing discharge side and a second opening in communication with the pump housing suction side; a wax thermostatic element disposed within the shell bore; a thermostatic actuator piston movably disposed within the shell bore adjacent the thermostatic element so that expansion of the wax thermostatic element under elevated temperature conditions moves the thermostatic actuator piston from a first position to a second position; a poppet movable between a closed position and an open position and disposed within the shell bore adjacent the thermostatic actuator piston so that movement of the thermostatic actuator piston from the first position to the second position causes the poppet to move from the closed position to the open position, wherein the poppet prevents fluid flow between the first and second shell openings in the closed position and the poppet permits fluid flow between the first and second shell openings in the open position; a thermostatic relief valve shell having an elongate inner bore, a first opening in communication with the pump housing discharge side and a second opening in communication with the pump housing suction side; a wax thermostatic element disposed within the shell bore; a thermostatic actuator piston movably disposed within the shell bore adjacent the thermostatic element so that expansion of the wax thermostatic element under elevated temperature conditions moves the thermostatic actuator piston from a first position to a second position; a poppet movable between a closed position and an open position and disposed within the shell bore adjacent the thermostatic actuator piston so that movement of the thermostatic actuator piston from the first position to the second position causes the poppet to move from the closed position to the open position, wherein the poppet prevents fluid flow between the first and second shell openings in the closed position and the poppet permits fluid flow between the first and second shell openings in the open position; and a thermostatic actuator return spring disposed within the shell bore and biased against at least a portion of the thermostatic actuator piston for returning the thermostatic actuator piston from the second position to the first position; characterized in that a poppet return spring is disposed within the shell bore and biased against the poppet for returning the poppet from the open position to the closed position.