What was found
DURING TAKEOFF, FUEL ON THE NR 2 SIDE WAS NOTED TO BE 100 LBS LESS THAN THE NR 1 SIDE. ABOUT 20 MINS AFTER TAKEOFF FUEL IMBALANCE ON EICAS. SELECTED TRANSFER OPEN TO REBALANCE FUEL. WHEN FUEL BACK IN BALANCE BOTH ENGINES WERE INDICATING SAME FUEL FLOW. STARTED CLOCK. AFTER 30 MINUTES FUEL WAS 200 LBS OUT OF BALANCE. VISUAL INSPECTION OF OF RIGHT WING CONFIRMED FUEL LEAKAGE IN THE VICINITY OF THE FUEL VENT. ADDITIONALLY FUEL APPEARED TO BE LEAKING FROM BOTH SIDES OF ENTIRE PYLON. ESTIMATED LEAK RATE AT 400 LBS PER HOUR; REMOVED AND REPLACED FLOAT ACTUATED DRAIN VALVES ON WING VENT STUB DRAIN LINE AND MAIN VENT LINE IAW AMM 28-12-03-000-801-A AND 28-12-03-400-801--A.REMOVED AND REPLACED FLOAT VENT VALVE AT R/WING IAW AMM 28-12-05-400-801-A AND 28-12-05-000-801-A