What was found
AFTER 1 HR 30 MINUTES FLIGHT, A/C RETURN BACK TO STN DUE TO NR 3 HYD QTY LOW. FOUND HYD QTY 3 RESERVOIR DEPLETED TO 1.0 AND FOUND EXCESSIVE LEAK FROM THE NR 1 HORIZONTAL STABILIZER CONTROL VALVE UNION. REQUIRES UNION O- RINGS, EDP PUMP AND FILTER MODULE. REMOVED AND INSTALLED BOTH ENGINE DRIVEN HYD PUMP ON NR 3 ENGINE AS PER AMM 29-11-20-4. REMOVED AND INSTALLED ALL THE FOUR HYD OIL FILTERS AS PER AMM 29-12-41-400. REPLACED HORIZONTAL PRIMER Y CONTROL VALVE UNION O-RING. REFILLED NR 3 HYD SYSTEM AS REQUIRED. RAN NR 3 ENGINE AS PER JRH. CYCLED HORIZONTAL STAB FEW TIMES. NO LEAK FOUND ON THE STAB CONTROL VALVE UNION. NR 3 SYSTEM HYD QTY REMAINED SAME. ENGINE RUN BY 245371.