What was found
LANDING GEAR FAILED TO RESPOND WHEN SELECTED TO UP POSITION AFTER TAKEOFF, SELECTOR HANDLE WAS CYCLED DOWN, THEN UP AGAIN WITH NO CHANGE. AS CREW WAS RUNNING CHECKLIST, GREEN HYDRAULIC SYSTEM HI TEMP WARNING CAME ON. CREW FOLLOWED CHECKLISTS FOR GREEN SYSTEM HI TEMP AND LANDING GEAR FAILURE TO RESPOND. DECLARED EMERGENCY AND LANDED AIRCRAFT SAFELY. MAINTENANCE WAS UNABLE TO DUPLICATE THE ISSUE ON THE GROUND, CONSULTED WITH MANUFACTURER AND CHANGED LANDING GEAR SELECTOR VALVE- BELIEVE VALVE ONLY PARTIALLY MOVED IN FLIGHT, CAUSING GEAR TO NOT MOVE AND THE HYDRAULIC FLUID BYPASSING THRU VALVE TO OVERHEAT THE HYDRAULIC FLUID. AFTER CHANGING SELECTOR VALVE, NO FURTHER FAULTS HAVE BEEN NOTED.