What was found
(CAN) WHILE ENROUTE THE CREW REPORTED A YELLOW SYSTEM HYDRAULICS QUANTITY LOSS, AFTER DISCUSSION WITH MAINTENANCE THE YELLOW SYSTEM WAS SHUTDOWN AND THE FLIGHT CONTINUED NORMALLY TO DESTINATION. MAINTENANCE ALSO SUGGESTED THE CREW SWITCH THE PUMPS BACK ON JUST PRIOR TO LANDING SO THEY WOULD HAVE FULL RT ENGINE REVERSE CAPABILITY AND FULL FLIGHT CONTROL USE, THEN SWITCH THE PUMPS OFF AFTER LANDING TO PREVENT POSSIBLE PUMP DAMAGE. FOUND CHECK VALVE LEAKING ON YELLOW HYD PTU MANIFOLD. O-RING REPLACED & CHECK VALVE RE-INSTALLED IAW AMM 29-13-15. OPS CHECK SERVICEABLE.