What was found
THE A-SYSTEM ENGINE DRIVEN HYDRAULIC PUMP LOW PRESSURE LIGHT ILLUMINATED WHILE EN ROUTE. THE A-HYDRAULIC SYSTEM WAS SHUT OFF AND THE QUANTITY DROPPED TO ZERO. THE AIRCRAFT WAS DIVERTED TO DEN WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE O-RING ON A SYSTEM ELECTRIC PUMP ACOUSTIC FILTER ASSEMBLY LEAKING. THE FILTER WAS REMOVED AND REPLACED. IN ADDITION, THE NR 1 ENGINE DRIVEN HYDRAULIC PUMP WAS REPLACED, LEAK AND OPERATIONAL CHECKS WERE GOOD.