What was found
AIRCRAFT WAS GROUNDED. EMERGENCY LANDING DECLARED ON ARRIVAL INTO MIA ACCOUNT LOW PRESSURE YELLOW HYDRAULIC SYSTEM. FLIGHT LANDED WITHOUT INCIDENT AND TAXIED TO THE GATE. PERFORMED TROUBLESHOOTING AND PINPOINTED ACTIVE LEAK TO PTU MANIFOLD OF THE YELLOW HYDRAULIC SYSTEM AT THE REDUCER, FOUND PACKING DAMAGED AT REDUCER. REMOVED AND REPLACED PACKING, SERVICED HYDRAULIC SYSTEM. ACCOMPLISHED A SATISFACTORY LEAK/OPERATIONAL CHECK, PER AMM 29-13-15.