L DRAINED OUT. GAINED ACCESS TO L/H WING OUTBD VENT FLOAT VALVES AT RBS 428 AND VENT FLOAT RELIEF VALVE AT BL 12.5. UPON INSPECTION OF VALVES NOTED FWRD OUTBD VENT FLOAT VALVE AT ABS 428 TO NOT BE OPERATING SMOOTHLY. REMOVED VALVE P/N: L49700-3 S/N: 757. NOTED VALVE TO ACTUATE NORMALLY ON BENCH. RECIEVED OK AND REINSTALLE