What was found
(CAN) WHILE ENROUTE, THE CREW REPORTED THE YELLOW HYD SYS HAD NO FLUID LT. ALL LINE & FITTING TIGHTENED SMALL AMOUNT OF TRAVEL FOUND ON LARGE FITTING O-RING BELIEVED TO BE PIERCED. SOLENOID VALVE O-RING REPLACED. YELLOW HYD INDICATOR QTY ABOVE .2500, HYD TOPPED UP, ALL SYS OP & LEAK CK CARRIED OUT, NO FAULT, ALL HYD FILTER POPOUT, INDICATOR NORMAL, ACFT CONSIDERED SERVICEABLE.