What was found
(CAN) IN CRUISE, CREW NOTICE THAT THE HYDRAULIC LEVEL OF SYSTEM NR 2 WAS 0, THEY DECLARE AN EMERGENCY AND LANDED SAFELY. FURTHER INVESTIGATION, NO SIGN OF HYDRAULIC LEAK HAVE BEEN FOUND. THE AIRCRAFT NR 2 HYDRAULIC SYSTEM WAS SERVICED, SYSTEM WAS TESTED ON THE GROUND, A TEST FLIGHT WAS CARRY OUT WITH NO SIGN OF LEAK. AIRCRAFT FLEW BACK TO IS BASE (2 1/2 HRS FLIGHT) FOR FURTHER INVESTIGATION, AND DURING THAT FLIGHT MAINTENANCE ON BOARD MONITORED THE QUANTITY, AND NO EVIDENCE OF LEAK WAS NOTED. ENVIRONMENTAL CONTAINER OF NR 2 NACELLE WAS VERIFIED UPON ARRIVAL, AND LITTLE HYDRAULIC FLUID WAS FOUND. THE ENGINE HYDRAULIC PUMP WAS REMOVED FOR INVESTIGATION, AND THE PUMP SHAFT SEAL(PUMP SIDE) WAS FOUND DAMAGED.