Fault Phenomenon: Komatsu WA380 wheel loader during heavy loading, a loud noise occurs, one side of the bucket suddenly droops and cannot move.

Troubleshooting Process:
– Checked rocker arm: Z-linkage or main rocker arm body cracked or completely broken.
– Checked welds: original or repair welds torn.
– Checked pins: pins bent and deformed.
– Checked operation: prolonged overload or off-center loading.

Root Cause: The bucket rocker arm weld failed due to long-term fatigue stress concentration at critical load points, eventually tearing and breaking.

Required Parts: Cut out and replace bucket rocker arm assembly, re-weld and reinforce.