What was found
DURING A PREFLIGHT INSPECTION IT WAS NOTED THE PAINT ON THE LOWER SKIN OF THE LEFT PYLON WAS DISCOLORED AND BUBBLED UP. VISUAL INVESTIGATION REVEALED THE PRECOOLER ASSEMBLY HAD FAILED, ALLOWING BLEED AIR INTO THE 6312209-1, DUCT ASSEMBLY, WHICH CAUSED THE 6312209-1 DUCT ASSEMBLY TO FAIL, ALLOWING BLEED AIR INTO THE PYLON. A CONDUCTIVITY CHECK OF THE COMPONENTS WHICH MAKE UP THE PYLON, PYLON SKINS AND FUSELAGE SKINS IN THE AREA OF THE PYLON SHOWED MANY OF THE COMPONENTS TEMPERATURE TO HAVE CHANGED. THE FUSELAGE SKIN IN THE PYLON AND THE AREAS SURROUNDING THE PYLON WERE NOT AFFECTED BY THE HEAT.