A device seating a valve body with the aid of an urging force of a spring by stopping the operation of a pump, changes over an energization state of a coil of at least one of the liquid shutoff valves which is changed over to the closed-valve state where the coil is energized, and then resumes the operation of the pump. Upon detecting the start of operation of the pump, a valve control unit causes a pump control unit to perform opening-closing force-feed control, where an amount of the cooling liquid force-fed by the pump is set to an amount within such a range that the valve body of the liquid shutoff valves whose coil is energized is not displaced in a valve-opening direction while the valve body of the liquid shutoff valves whose coil is not energized is displaced in the valve-opening direction.