What was found
DURING FLIGHT, CREW NOTICED A COMPLETE LOSS OF PRESSURE ON THE NR 3 HYDRAULIC SYSTEM, SUBSEQUENTLY, MAKING A PRECAUTIONARY UNSCHEDULED LANDING WITHOUT INCIDENT. AS HALF OF THE MAIN WHEEL BRAKES OPERATE FROM THE NR 3 HYDRAULIC SYSTEM AND THE OTHER HALF OPERATE FROM THE NR 2 SYSTEM, THIS LEFT ONLY HALF OF BRAKING SYSTEM TO STOP ACFT. INSP AND T/S REVEALED A SHAFT SEAL ON THE NR 3 HYDRAULIC MECHANICAL PUMP AND MOTOR ASSY WAS LEAKING DUE TO FAILING AND LOOSE MOTOR BEARING. REMOVED AND REPLACED NR 3 HYDRAULIC PUMP, PN 63108-06 AND MOTOR ASSY, PN 9008015-2; INSTALLING REPAIRED AND OVERHAULED UNITS.