What was found
REF LOG PAGE 446358, DURING CLIMB OUT, PILOT REPORTED AN ELECTRONIC CENTRALIZED ACFT MONITORING MESSAGE FOR "AIR ENGINE BLEED LEAK" AND MADE AN AIR RETURN TO DEPARTURE. MX REMOVED AND REPLACED THE NR 1 ENGINE PRECOOLER HEAT EXCHANGER ALONG WITH ASSOCIATED SEALS, IAW AMM 36-11-42 PB 401.