What was found
RECEIVED A LEFT BLEED DUCT WARNING MSG WHILE ENROUTE AT FL220. RAN QRH AND THEN QRC AS PLANE DEPRESSURIZATION. RETURNED TO AVOID FURTHER ICING CONDITIONS AND FOR MX CONSIDERATIONS. FLIGHT 5717. MDC REPORTES BLEED LEAK LOCATION AT LOOPS MT 138 AND MT 139. INSPECTED AND FOUND MT 138 LOOP HIGH RESISTANCE AND SMALL LEAK ON THE HIGH PRESSURE GROUND AIR DUCT. ALSO FOUND SMALL LEAK AT THE LEFT ENGINE COWL ANTI ICE VALVE DUCT BELLOWS WHERE MT 139 RUNS AND MISSING E-SEALS ON ANTI ICE VALVE CONECTION. REMOVED AND REPLACED LEFT BLEED LOOP MT 138 AND REMOVED AND REPLACED HIGH PRESSURE GROUND AIR DUCT. OPS CHECK AND LEAK CHECK GOOD IAW AMM.