Fault Phenomenon: Co-Nele KNL5400 rotates smoothly when cold. After continuous rotation operations (operating temperature), the boom rotation becomes jerky, cannot rotate smoothly, and eventually locks up.

Troubleshooting Process:
– Checked swing drive gear: gear meshing normal, no broken teeth.
– Checked swing bearing lubrication: sufficient grease, no dry running.
– Checked swing motor brake release: normal when cold.
– Measured brake release pressure at operating temperature: found pressure builds slowly and is insufficient.

Root Cause: Swing motor brake pads expand due to heat, causing the release clearance to disappear.

Required Parts: Swing motor brake component repair kit.