What was found
(CAN) SHORTLY AFTER TAKEOFF, THE FLT CREW REPORTED LOSS OF NR 3 HYDRAULIC PRESSURE. ALTRNATE LANDING GEAR EXTENSION CARRIED OUT IN ACCORDANCE WITH THE QRH. THE AIRCRAFT RETURNED TO ORD AND LANDED WITHOUT FURTHER INCIDENT. UPON FURTHER INVESTIGATION, A LEAK WAS FOUND AT THE 3A PUMP/ACOUSTIC FILTER ASSY. BOTH 3A AND 3B PUMPS WERE REPLACED. THE NR 3 HYD SYSTEM WAS RESERVICED AND OPS CHECKED IN ACCORDANCE WITH THE AMM AND THE AIRCRAFT WAS RETURNED TO SERVICE.