What was found
SHORTLY AFTER DEPARTURE AT FL170 RECEIVED HYD 3 ELEV OFF. WE NOTICED THE HYD 3 FLUID DECREASING RAPIDLY BELOW 4 GALLONS, WENT THROUGHT THE VARIOUS HYD CHECKLISTS. "HYD 3 ELEV OFF" LEVEL ONE THE "HYD QTY LOW" THE "HYD 3 FAIL". COMPLETED QRH AND DID MANUAL GEAR EXTENSION, AS PER CHECKLIST. WALK AROUND SHOWED SYSTEM 3 RESERVOIR TOTALLY EMPTY OF FLUID. NO LEAKS SHOWING FORWARD OF AND INCLUDING APU AREA. COMPARTMENT OF RMP 2-3 AND RESERVOIR NR 2 SHOWS SIGNS IN LOWER PORTIONS OF EXCESS HYDRAULIC LEAK. DURING REFILL OF NR 3 SYSTEM, HYDRO FLUID BEGAN FLOWING OUT OF COMPARTMENT JUST FORWARD OF APU MAIN DOOR. FOUND RIGHT STAB TRIM MOTOR O-RING BLOWN OUT AT THE BASE. WE HAVE MOTOR W/KIT IN STOCK IND.