A B777-200 FLIGHT CREW REPORTS ALL FIRE DETECTION ABILITY WAS LOST ON #2 ENG. ALSO; ENG STATUS AND EICAS MESSAGES APPEARING THEN DISAPPEARING; INCLUDING THE OVERHEAT CIRCUIT; FIRE WARNING LOOP AND ENG IGNITER.

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ENRTE ALL FIRE DETECTION ABILITY WAS LOST ON THE #2 ENG. WE DECIDED TO RETURN TO ZZZ. DISPATCH; MAINT; AS WELL AS THE DUTY MGR WERE ALL CONSULTED DURING THE DECISION MAKING PROCESS. RERTE; AND RETURN TO ZZZ WERE ALL UNEVENTFUL. A VARIATION OF THIS MAINT ISSUE HAD SURFACED 3-4 TIMES ON THIS ACFT OVER THE PRECEDING COUPLE OF DAYS NEVER HAVING BEEN FULLY RESOLVED. THIS PARTICULAR EVENT ACTUALLY INCLUDED THE COMPLETE FAILURE OF BOTH FIRE LOOPS INSTEAD OF JUST ONE WHICH HAD OCCURRED PREVIOUSLY. SUPPLEMENTAL INFO FROM ACN 771995: APPROX 1 HR W OF ZZZ OVER THE OCEAN; NOTICED 3 STATUS MESSAGES: OVERHEAT CIRCUIT R2; FIRE LOOP 2 ENG R; ENG IGNITER R1. (THE FIRST 2 STATUS MESSAGES WERE PREVIOUS WRITE-UPS.) SEVERAL SECONDS LATER; THE EICAS MESSAGE 'DET FIRE ENG R' APPEARED AND THEN DISAPPEARED. WHEN THIS EICAS MESSAGE APPEARED; THE STATUS MESSAGES: OVERHEAT CIRCUIT R2 AND FIRE LOOP 2 ENG R DISAPPEARED. LATER THESE STATUS MESSAGES REAPPEARED. CALLED MAINT CTL AND THE DISPATCHER. THEN CONSULTED WITH THE DUTY MGR. THEY DECIDED IT WAS UNWISE TO CONTINUE AND RECOMMENDED THAT WE RETURN TO ZZZ. WE CONTACTED ATC VIA CPDLC. IT TOOK APPROX 8 MINS TO GET A RERTE BACK TO ZZZ. ON RETURN LEG TO ZZZ; GOT THE SAME EICAS MESSAGE OF DET FIRE ENG R WHICH THEN DISAPPEARED.