AN MDT CREW ENRTE JFK TO EGGW (LONDON) EXPERIENCED AN ENG DRIVEN HYD PUMP FAILURE; REQUIRING ENG SHUTDOWN AND A DIVERSION TO THEIR ALTERNATE.

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WHILE ENRTE FROM JFK TO LONDON LUTON (EGGW) ON TRACK (NAT) AT APPROX 30 W; A CAUTION MESSAGE ON EICAS 'HYD 2 LOW PRESSURE' CAME ON. INVESTIGATION REVEALED AN ALMOST COMPLETE LOSS OF #2 HYD SYS FLUID. SYS PRESSURE WAS FALLING BELOW 1800 PSI. THE ABNORMAL CHKLIST WAS PERFORMED. AT THAT TIME WE (THE CREW) NOTED AN INCREASE IN THE REMAINING FLUID TEMP. AT THAT TIME; I FELT THAT THE ENG DRIVEN PUMP WAS OVERHEATING DUE TO THE LACK OF FLUID. BASED ON PREVIOUS EXPERIENCE WITH THIS CONDITION; I DECIDED TO SECURE THE #2 ENG TO PREVENT FURTHER DAMAGE TO THE PUMP AND RELATED SYS. WX WAS GOOD ENRTE AND AT ALTERNATE SHANNON. SHANWICK ATC WAS ADVISED OF OUR SIT. CLRNC TO DSND TO FL280 (SINGLE ENG CRUISING ALT FOR OUR WT AND TEMP) WAS REQUESTED AND GRANTED. DIVERSION TO NEAREST SUITABLE ARPT; SHANNON; WAS ALSO REQUESTED AND GRANTED. SHANWICK ASKED US IF WE WANTED TO DECLARE AN EMER. I REPLIED 'AFFIRMATIVE.' THE FLT TO SHANNON WAS COMPLETED ON SINGLE ENG WITHOUT ANY FURTHER PROBS. POSTFLT REVEALED A RUPTURED PIPE IN THE REAR BAY. A CALL TO MY CHIEF PLT FOLLOWED. HE EXPRESSED CONCERN AT MY WILLINGNESS TO DECLARE AN EMER FOR THE ABOVE EVENT. I STAND BY MY DECISION. THE DECLARATION OF THE EMER ALERTED ALL PARTIES INVOLVED IN CASE THE SIT GOT WORSE. NO ATC CLRNCS WERE VIOLATED; ALL ACTIONS WERE COORDINATED WITH ATC. I FELT THAT THE DECLARATION OF AN EMER ADDED A LEVEL OF SAFETY TOWARD THE COMPLETION OF OUR FLT.