What was found
ON APPROACH, CREW REPORTED HYD SYS NR 3 LOW PRESSURE MESSAGE CAME ON WHEN LANDING GEAR SELECTED DOWN. CREW LANDED AND USING DIFFERENTIAL BRAKING, TAXIED TO GATE. MAINTENANCE TROUBLESHOT AND FOUND LEAK ON AFT SIDE OF ALTERNATING CURRENT MOTOR PUMP, ACMP, 3B. MAINTENANCE R & R PRESSURE HOSE AND ACMP 3B AND PERFORMED CHECKS IAW AMM. REPLACEMENT OF PUMP WAS DUE TO HAVING BEEN RUN WITHOUT FLUID. ACFT RELEASED FOR SERVICE.