Fault Phenomenon: Hiab 958 after 1 hour of continuous operation, hydraulic oil temperature exceeds 90°C, actions slow.

Troubleshooting Process:
– Checked cooler fan: fan motor burnt.
– Checked cooler fins: clogged with oil sludge.
– Checked relief valve: set pressure too high, causing internal leakage and heat generation.
– Replaced fan motor, cleaned cooler, adjusted relief pressure.

Root Cause: Cooling fan failure and system pressure set too high.

Required Parts: Cooling fan motor, hydraulic oil.