What was found
STATION REPORTED SMOKE FROM LT MAIN GEAR ON TAXI OUT. ON RETURN TO GATE, HYD SYS 2 FLUID LEVEL OBSERVED TO DROP RAPIDLY AFTER SETTING PARKING BRAKE. IN CONJUNCTION WITH EICAS MSG EMRG BRK LOW PRESS & HYD SYS 2 FAIL, POST FLIGHT SHOWED SIGNIFICANT FLUID PUDDLE UNDER LT GEAR MISSING BOLT & LOOSE METAL PLATE ABOUT 1 CM SQUARE ON INSIDE RIM OF RT TIRE & LT GEAR & EXTENSION METAL SHA. R & R NR 2 BRAKE IAW WC 32-600-14. R & R NR 1 LT MAIN WHEEL PN 31641 SN 32940083P & NR 2 MLG WHEEL ASSEMBLY PN 31641 SN 22490427P IAW WC 32-700-11. SERVICED NR 2 HYD SYS IAW AMM 12-13-01. ALL OPERATIONS & LEAK CHECKS, NO DEFECTS NOTED AT THIS TIME.