Fault Phenomenon: Co-Nele KNL5400 swing functions normally when cold. During continuous swing operations (operating temperature), the swing gearbox leaks oil, oil level drops, and eventually fails.

Troubleshooting Process:
– Checked gearbox breather: breather unobstructed.
– Checked oil seal: seal lip intact.
– Checked mating surfaces: surfaces not deformed.
– Measured internal pressure of the gearbox at operating temperature: found pressure too high.

Root Cause: The gearbox breather is blocked, causing internal pressure to build up from thermal expansion, blowing out the oil seal.

Required Parts: Swing gearbox breather and oil seal.