Fault Phenomenon: The XCA350L8 exhibits slow arm dropping during luffing action, sinking even when locked.

Troubleshooting Process:
– Check luffing cylinder seal: Found wear.
– Check counterbalance valve: No abnormalities.
– Disassembled cylinder and replaced seals.
– Disappearance of arm drop confirmed after re-testing.

Root Cause: Aging piston seals in luffing cylinder causing internal leakage.

Required Parts: Cylinder seal kit, hydraulic oil.