What was found
LEFT HYD SYSTEM LOW PRESSURE MESSAGE ON DOWNWIND. QRH COMPLETED, ALTERNATE FLAPS AND GEAR USED. FOUND THE LT HYD SYSTEM DIFFERENTIAL PRESSURE INDICATOR LEAKING AT MODULE IN THE LT ENGINE PYLON. R & R THE LEFT ENG FILTER MODULE PRESSURE FILTER, DIFFERENTIAL PRESSURE INDICATOR IAW MM 29-11-17-4. SERVICED LEFT HYDRAULIC RESERVIOR IAW MM 12-12-01-3. PRESSURIZED HYDRAULICS AND CYCLED FLAPS TWO TIMES IAW MM 27-51-00-5, WITH NO PROBLEMS. LEAK CHECKED GOOD. OK FOR SERVICE.