What was found
L BLEED DUCT WARNING MESSAGE AFTER COWLS TURNED ON. BLEEDS CLOSED AUTOMATICALLY, PRESSURIZATION LOST. QRH COMPLIED WITH. (FLIGHT 6484 - FILED CLOSED)THIS DISCREPANCY WAS TRANSFERRED TO CAMP ITEM 30299218 WITH THE FOLLOWING CORRECTIVE ACTION: "INTERROGATED MDC FOUND B1-349536. TROUBLESHOT L BLEED DUCT WARNING PER FIM 36-21-01-810-813. PERFORMED EVENT LOCATION HISTORY TEST IAW FIM AND FOUND L BLEED LOOP A "LEAK" AT MT 141 23%. PERFORMED LEAK CHECK OF BLEED COMPONENTS NEAR INDICATED LEAK IAW FIM, NO LEAKS NOTED. PERFORMED INSPECTION OF LOOPS A AND B NEAR, FOUND LOOP B TOUCHING COMPONENT NEAR INDICATED 23%, REPOSITIONED LOOP B IAW AMM 36-21-00. REMOVED AND REPLACED BOTH CERAMIC INSERTS OF APU DUCT BLEED AIR LOOP A IAW AMM 36-21-00, NO FIX. REMOVED AND REPLACED APU DUCT BLEED AIR LOOP A MT141 IAW AMM 36-21-1, OPS CHECK GOOD. PRESSURIZE AIR CONDITIONING SYSTEM IAW AMM 21-50-00, L BLEED DUCT WARNING MESSAGE DID NOT RETURN. OPS CHECK GOOD AT THIS TIME. "