What was found
(CAN) THE PILOT REPORTED UPON APPROACH, THE MLG DID NOT EXTEND AND THE DISAGREE MSG APPEARED. A SECOND ATTEMPT PRODUCED THE SAME RESULTS. THE LANDING GEAR WAS SUCCESSFULLY EXTENDED MANUALLY IAW EMERGENCY PROCEDURE. THE AIRCRAFT RETURNED TO SERVICE FOLLOWING REPLACEMENT OF THE FOLLOWING PARTS. MLG SELECTOR VALVE, P/N 750005000, S/N 0828 MLG PRIORITY VALVE, P/N 4619-3, S/N 1157 NLG PRIORIY VALVE, P/N 4622,S/N 1172 NOTE: DURING INSPECTION/TROUBLESHOOTING OF THE AIRCRAFT BY THE MECANIC, EVIDENCE OF HEAVY HYD LEAKAGE WAS FOUND AT THE MLG SELECTOR VALVE.