What was found
BLEED DUCT WARNING AND ASSOCIATED LT BLEED DUCT CAUTION MESSAGE DURING CLIMB THROUGH FL300. RAN QRH & MESSAGE CLEARED. (FLIGHT 6281) SEE ML 1808395 FOR PREVIOUS TROUBLESHOOTING.PERFORMED AN OPS TEST OF THE AIR-CONDITIONING DISTRIBUTION SYSTEM IAW AMM 21-51-00 & CONFIRMED LEAK COMING FROM LT HOT AIR SHUT-OFF VALVE. FOUND INSULATION MUFF TO BE DAMAGED & FOUND UPPER & LOWER COUPLINGS LOOSE. TORQUED UPPER & LOWER COUPLINGS TO SPECS AND R & R INSULATION MUFF IAW AMM 21-61-08. LEAK TEST & OPS TESTED GOOD. NO LT BLEED DUCT WARNING & ASSOCIATED LT BLEED DUCT CAUTION MESSAGE DURING OPS CHECKED. ACFT OK FOR CONTINUED SERVICE.