What was found
IN CRUISE FL 290 LEFT WING OVERHEAT LIGHT ILLUMINATED, COMPLIED WITH WING OVERHEAT PROCEDURE ISOLATED LEFT WING AND NR 1 AND NR 2 ENGINES WITH PYLON VALVES LIGHT WENT OUT. RETURNED THRUST TO NORMAL, LIGHT STAYED OUT. FOUND PNEUMATIC LEAK 1 FOOT INBOARD OF NR 4 LEFT LEADING EDGE DEVICE LEAK WAS BLOWING AIR ON OVERHEAT SWITCH. RESEALED DUCT AND LEAK CHECKED PER M/M 36-11-01 AND 36-11-00.