What was found
BLUE HYD SYS, AIR TURN BACK. LOST BLUE HYR PRESSURE AFTER TAKEOFF. ON RETURNING TO GATE FOUND HYD LEAK IN LT WHEEL WELL AFT BULKHEAD. LEAK FROM BLUE SYS MANIFOLD L/E FLAP PRIORITY VALVE. NEEDS VALVE-NIS MSN. BLED RESERVOIR PRESS AND REMOVED PRIORITY VALVE FROM MANIFOLD IAW AMM 29-12-12-04. OLD PART & HARDWARE PLACED ON WORK BENCH IN SHOP. CLEANED WHEEL WELL AREA IAW SMP. AWAITING PARTS ARRIVAL. INSPECTED BLUE HYD SYS IAW AMM 29-00-00-03 12 D. (2) OPERATION OF PUMP WITH LOW FLUID LEVEL. ALL CLOGGING PDI'S CHECKED NORMAL AND FLUID LEVEL IS ABOVE MINIMUM GAUGEABLE LEVEL. R & R BLUE L/E FLAP PRIORTY VALVE. OPS AND LEAK CK NORMAL IAW MM 29-12-12-04 AND JRH .