What was found
ON FLIGHT 3655 THE CREW REPORTED WHILE EN ROUTE A "BLEED 1 LEAK" MESSAGE ILLUMINATED. THE CREW FOLLOWED AIRCRAFT OPERATIONS MANUAL VOLUME 1 AND DE-SELECTED BLEED 1 AND WAITED 3 MINUTES, THE FAULT REMAINED. THE CREW DE-SELECTED THE NR 2 BLEED SWITCH AND WHILE WAITING THE 3 MINUTES THE FAULT CLEARED. THE CREW ELECTED TO RETURN TO MIA. THE CREW DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. FOUND O-RING DAMAGED IN BLEED AIR TUBE UNDER CARGO FLOORBOARD NR 272AF. REPLACED O-RING PER AMM 36-11-10. THE OPERATIONAL CHECK WAS GOOD. NO OVERWEIGHT LANDING LESS THAN 300 FEET PER MINUTE. THE AIRCRAFT WAS RETURNED TO SERVICE.