1. Firstly, check the oil level. If the oil level is below the minimum mark, additional oil should be added.

2. If the oil level is normal, the inlet and outlet pipes should be checked for leaks. If there are leaks, they should be repaired or replaced.

3. If the inlet and outlet pipelines are well sealed, check the working condition of the inlet and outlet pressure valves. If the inlet and outlet pressure valves cannot be closed, they should be removed and checked for cracks or scars on the upper components, smooth oil circuits and holes, and reduced spring stiffness. Handle this issue promptly.

4. If the pressure valve is normal, the oil pipe or filter should be removed for inspection. If there is blockage, it should be cleaned and sediment removed.

5. If the oil pipe is unobstructed, check the hydraulic pump and replace it if necessary.

6. If the hydraulic oil bubbles, the installation of the oil pipe should be checked. If the oil level in the return pipe is lower than the oil level in the tank, the return pipe should be reinstalled.