What was found
(CAN) AT TRANSITION TO CRUISE FL 350 AFTER DEPARTURE, THE NR 2 ENGINE APPEARED TO SURGE OR COMPRESSOR STALL. AFTER 2 ATTEMPTS TO REDUCE THROTTLE THE ENGINE WAS SHUTDOWN AND THE AIRCRAFT RETURNED TO POINT OF DEPARTURE. MAINTENANCE FOUND A LEAK AT THE PS4 FITTING AT THE PRESSUE RATIO BLEED CONTROL (PRBC). THE O-RING WAS REPLACED AND THE FITTING RESECURED. AIRCRAFT WAS GROUND CHECKED WITH NO FURTHER PROBLEM AND RETURNED TO SERVICE.