Apparatus for draining a cooling system

A drain valve assembly comprising a housing containing

• a. a manifold passage provided with a plurality of ports which lead to the exterior of the housing;
• b. a depending drain passage leading from the manifold passage to the exterior of the housing;
• c. a rotary, plug type drain valve arranged to open and close the drain passage;
• d. motor means effective when energized to open the drain valve but being ineffective to close that valve, the motor means comprising a single-acting fluid pressure actuating motor having a working space and a movable member which responds to the pressure in that space and is connected to open the drain valve;
• e. a pilot valve provided with a supply passage, an atmospheric vent passage, and a motor passage connected with the working space, and including a control member movable between vent and supply positions in which, respectively, it connects the motor passage with the vent and supply passages;
• f. means biasing the control member to the vent position, and a solenoid for shifting the control member to the supply position;
• g. a manually operated valve actuator located outside the housing and coupled with the drain valve for opening and closing same, but being effective to close the drain valve only when the working space of the fluid pressure actuating motor is vented;
• and
• h. an electrical circuit having at least a pair of terminals leading to the exterior of the housing and which are interconnected by a loop containing the solenoid and a normally open switch means.