As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT CREW REPORTED THAT THE CENTER HYDRAULIC SYSTEM WAS LOOSING QUANTITY AND WOULD LIKELY BE EMPTY UPON ARRIVAL INTO ORD. DELCARED EMERGENCY AND LANDED WITHOUT INCIDENT. TROUBLESHOT THE FAULTY/LEAKING DELTA-P AT PRESSURE AND CASE DRAIN FILTER AC MOTOR PUMP C2. REPLACED CASE DRAIN FILTER IAW AMM 29-11-18. OPS AND LEAK CHECKED GOOD. AC OK FOR SERVICE. THE AIRCRAFT WAS GROUNDED.