What was found
ENGINE NR 1 STRUT OVERHEAT ILLUMINATED. WHEN NR 1 BLEED WAS CLOSED, LIGHT WENT OUT, FINISHED CHECKLIST RESULTING IN RIGHT PACK AND NR 3 BLEED ONLY USABLE. FOUND SENSE LINE ON NR 1 ENGINE BLEED AIR SHUTOFF VALVE LOOSE, (B-NUT WAS BACKED OFF). TIGHTENED SENSE LINE, RAN ENGINE ON GROUND. NO BLEED LEAKS NOTED. OK FOR SERVICE.