What was found
UPON SELECTING GEAR LEVER TO THE DOWN POSITION, RECEIVED GEAR DISAGREE MASTER WARNING, MAIN GEARS NOT LOCKED IN POSITION. PULLED EMERGENCY EXTENSION TO CW QRH, ALL GEAR DOWN AND LOCKED. AIRCRAFT REMOVED FROM SERVICE. 6028 - RECEIVED HYD 3 LO PRESS CAUTION MSG. CW QRH AND OBSERVED HYD SYNOPTIC PAGE SHOWED 0% QTY AND OBSERVED LO PRESSURE. ON THE GROUND RECEIVED HYD 3 HI TEMP CAUTION AND FLUID PUDDLE UNDER LH WING WING ROOT. R/R HYD PUMP 3A AND PERFORMED FLUSH DRAIN AND FILL IAW AMM 29-12-03, AWAC SUP 06-031D, 08-037F LEAK AND OPS CHECK GOOD.