What was found
(CAN) APPROX 20 MINS OUT CREW HAD A YELLOW HYD FAILURE & DECLARED A PAN PAN WITH ATC NO CFR TRUCKS WERE REQUESTED. ACFT LANDED WITHOUT INCIDENT & WAS ABLE TO TAXI & BRAKE WITHOUT A TOW TO GATE. RESOLUTION CREW SELECTED EDP OFF, YELLOW SYS WAS NOT EMPTY ON ARRIVAL. YELLOW ELEC PUMP OPERATED ON GND FOR TROUBLESHOOTING. PTU MANIFOLD CHECK VALVE 93094GM, O RING FAILED. O RING REPLACED IAW AMM SUBTASK 29-13-15-50-050-B. PTU OPERATIONS CHECK IAW AMM 29-23-00-710-002, SERVICEABLE.