What was found
ON CLIMBOUT, APPROXIMATELY 5 MINUTES AFTER CLOSING NR 1 BLEED AND OPENING NR 2 BLEED AT 18,000 FT LOWER AFT BODY OVERHEAT LIGHT ILLUMINATED. INITIATED CHECKLIST. AFTER SWITCHING TO NR 1 BLEED, LIGHT EXTINGUISHED. NOTED L-PACK AT 145 DEG C. PARTIALLY OPENED LEFT PACK COOLING DOOR, TEMPERATURE CAME ON TO 100, SWITCHED BACK TO 2 BLEED WITHOUT INCIDENT. FOUND AN AIR LEAK AT 8TH STAGE DUCT OF ENGINE 1 IN THE AFT AIRSTAIR AREA (CLAMP CRACKED). REMOVED AND REPLACED CLAMP, GROUND CHECK GOOD. NO FURTHER LEAK NOTED.