If it is confirmed through troubleshooting that the bucket overturning is normal due to the hydraulic system failure and only the boom lifting is slow and weak. This shows that the working pump and the main safety valve are working normally. It also shows that the oil quantity and quality of the pipeline and oil filter at the oil inlet end of the pump as well as the oil tank are all right. At this time, it is only necessary to check the boom spool valve, boom oil cylinder, boom oil pipe and its seals. The leakage of the boom spool valve is mainly due to the large fitting clearance between the valve rod and the valve body, the damage of the pressure regulating spring, and the damage of the seals in the valve. Check the fit clearance between valve rod and valve body. And check the pressure spring. Check whether the seal in the valve body is damaged. If the leakage test result in the oil cylinder exceeds the specified value, it shall be disassembled for further inspection. Replace the sealing ring if it is damaged. Replace the cylinder wall if it is seriously worn. Replace the boom valve if it is seriously worn.
