What was found
AFTER TAKEOFF, THE CREW COULD NOT RETRACT THE NOSE GEAR. THE GEAR WAS RECYCLED WITH NO SUCCESS. THE CREW RETURNED TO LAND AT DEPARTURE AIRPORT. THE NLG UPLOCK ASSEMBLY WAS REPLACED AND A LANDING GEAR SWING CARRIED OUT. DESCRIPTION/ROOT CAUSE, THE UNIT WAS SENT FOR REPAIR WITH THE REQUEST FOR A TEARDOWN REPORT. THE UNIT WAS PRE-TESTED AND FAILED THE LOCKING TEST. THE LOCK MECHANISM INSIDE THE UNIT FAILED TO LOCK THE HOOK. THE REPAIR FACILITY CONCLUDED THAT THE DRIED GREASE CAUSED THE LOCKING MECHANISM TO HANG UP AND PREVENTED THE HOOK FROM LOCKING THE NOSE LANDING GEAR. THE WEAR TO THE UNIT WAS NORMAL AND NO OTHER MECHANICAL DIFFICULTIES WERE OBSERVED. AT TIME OF THIS REPORT THE REPAIR ORGANIZATION WAS AWAITING INSTRUCTIONS TO PROCEED WITH REPAIR AND OR OVERHAUL. (TC NR 20080228001)