What was found
GSO - FLT 1046 - EN ROUTE MCO TO LGA, A-HYDRAULIC SYSTEM LOW PRESSURE LIGHT ILLUMINATED. HYD SYSTEM QTY WENT FROM 4 TO 1.5 GALLONS. DECLARED EMERGENCY AND DIVERTED TO GSO LANDED WITHOUT INCIDENT. MX REMOVED AND REPLACED NR 2 ENG DRIVEN HYD PUMP, REPLACED CASE DRAIN FILTER, AND A-SYSTEM RETURN AND PRESSURE FILTERS. FLUSHED SYSTEM AND PROGRAMMED FOR FILTER CHANGE. NO CONTAMINATION OR LEAKS NOTED. OPER CHK GOOD. NOTE: PREVIOUS FLT HAD A HYD PROBLEM. SYSTEM A-HYDRAULIC PRESSURE WENT TO ZERO. SYSTEM A-PUMPS SHUT OFF. GEAR AND FLAPS LOWERED BY ALTERNATE SYS. MX FOUND NR 1 ENGINE HYD PUMP CASE DRAIN LEAKING. REPLACED SAME. (X)