i HAVE ONE OF YOUR AIR SEPARATION VALVES IN MY SYSTEM THAT ALSO HAS DIRT IN CIRCULATION. AIR AND WATER NO LONGER COME OUT OF THE VALVE WHEN THE COVER SCREW IS REMOVED. IF I PRESS DOWN ON THE RELEASE VALVE WITH A SCREW DRIVER, HOT WATER EXITS, BUT STOPS ONCE I RELEASE. WHAT CAN BE DONE?
THANKS