1. Insufficient hydraulic oil will cause abnormal sound of oil pump. Check whether the oil is enough;
2. If the hydraulic oil is dirty and blocks the filter screen at the oil suction port, it will cause abnormal sound of the oil pump, and the oil cylinder motor and other components are unable to work. In this case, clean the filter screen, filter the hydraulic oil or replace the hydraulic oil;
3. If the oil pump is damaged, the inner surface of the stator of the vane pump will make abnormal noise, and if the plunger inside the plunger pump is damaged, it will make abnormal noise and vibrate severely. In this case, the pressure of the hydraulic system will be unstable, which may be caused by the hard objects in the hydraulic oil stuck in the pump.