What was found
ON CLIMBOUT, GOT HYD 3 ELEV OFF ALERT WITH DECREASING HYD 3 QTY. FOLLOW ON ALERTS HYD 3 OFF AND ON FINAL APPROACH BACK TO DEPARTURE GOT HYD 3 FAIL. LOST ALL HYD 3 QTY. ALTN GEAR EXTENSION USED. LDG WT 343,500LBS. AIRPORT CRASH FIRE RESCUE REPORTED SMOKE COMING OFF RT GEAR AND SPRAYED IT. FOUND SOURCE OF HYD FLUID LOSS TO BE THE RT GEAR TRIM CYL PRESSURE RELIEF VALVE. REPLACED SAME. SERVICED AND BLED HYD SYS 3. EXCERCISED ALL FLIGHT CONTROLS AND GEAR. CLEANED RIGHT GEAR WELL. ITEM OK FOR SERVICE. RESET ALT GEAR EXTENSION REF AMM'S 12-13-02-3, 12-22-02-7 & 32-37-03-2.