What was found
2.5 HRS IN FLIGHT RECEIVED "HYD 2 OFF" ALERT. NR 2 PUMPS OFF, QTY AT 2.7 GAL ON APPROACH EXTENDING SLATS, HSC TURNED 3/2 RMP ON, PRESSURIZED HYD 2 SYS. ONCE FLAPS WERE EXTENDED NR 2 QTY WENT TO 2.0 GAL, RECEIVED "QTY 2 LO" ALERT, AND HYD 2 FAIL ALERT. FOUND LEAK ON NR 2 ENGINE UPPER HYDRAULIC MODULE. REPLACED O-RING SEAL ON HYD PRESS MODULE UNION TO LEFT HYD PUMP AND PRESS LINE FROM HYD PRESS MODULE TO LEFT PUMP (UPPER) PER MM 29-11-20-4-2 AND MM 29-12-30-2-1. RAN ENG PER JRH CHAPT-6. ALL CHECK GOOD.