Abstract: A release valve for a self-priming pump includes a housing, a valve member, an exhaust outlet, a guide stem, a spring, and a bellows. The valve is positioned in a valve opening in the housing and is movable between an open and a closed position. The open position permits the travel of air and fluid through the opening. The closed position closes the valve opening. The valve plug is positioned in the valve opening responsive to pressure in the flow passageway of the housing. The guide stem is coupled to the valve plug and the spring is coupled to the guide stem. The bellows surrounds the spring.