What was found
AIRCRAFT WAS GROUNDED. EMERGENCY DECLARED. DFW-SNA FLIGHT DIVERTED TO ELP ACCOUNT PASSENGERS IN ROWS 17 AND 18 REPORTED THUMPING NOISE COMING FROM FLOOR, LANDING UNEVENTFUL. INSPECTED AIRCRAFT AND FLIGHT CONTINUED TO SNA. FOUND A LOOSE B-NUT AND MISSING CLAMP ON THE LEFT HYDRAULIC RESERVOIR HEAD PRESSURE LINE. TIGHTENED B-NUT (AALA20170501004) AND INSTALLED CLAMP. NO OTHER DEFECTS NOTED. OPERATIONAL CHECK GOOD.