Fault Phenomenon: Kobelco CK2500 during operation, the main hydraulic pump emits a high-pitched whine, system pressure fluctuates.

Troubleshooting Process:
– Checked hydraulic oil level: level too low, suction pipe exposed.
– Checked suction line: found loose fitting causing air ingress.
– Added hydraulic oil and tightened suction line fitting; after bleeding, noise disappeared.

Root Cause: Low hydraulic tank oil level and air ingress into the suction line caused pump cavitation.

Required Parts: Anti-wear hydraulic oil.