In 97, Shanghai Santana GLi car, the cumulative driving 122 thousand km, the engine at idle running, turn the power pump to send a "buzzing" sound, when turning around the steering wheel, the noise is aggravated. In 1 months, the car changed 2 steering pumps and changed up to first steering pumps. It took about 20 days of noise, and second had the same problem for 7 days. According to the maintenance technicians, they have regular purchase channels, and have sold many of these accessories. None of them has had similar problems. The pump body changed by dismantling has not been found. The vehicle is stopped on the flat surface, through a comprehensive visual inspection, it is found that the hydraulic pipeline, the pump body and the direction machine have no oil leakage. The hydraulic oil in the storage tank is between the upper limit and the lower limit, the transmission belt is tight and moderate, but the hydraulic oil is black and metamorphic phenomenon. Through the test, the turning steering wheel was turned around and turned to normal adding force. It turned stable and flexible in the driving. It had no deviation, heavy and fluttering, and turned back to good. Is it really the noise generated by the abnormal wear in the pump? According to the owner of the new pump, no oil leakage phenomenon has been found. The pump is only used for less than 10 days, and should not be caused by wear in the pump. If the pressure valve and the flow valve in the pump are bad, the pressure will be too low and the steering is heavy. If the pressure is too high, the pressure will be too big because of the power cylinder. It will appear in the direction automatically. If the steering valve is bad or internal leakage, it will turn to heavy; if the diversion valve is stuck, it will stagnation, It will lead to bad steering position. If the gap between the spool valve and the valve sleeve is not good enough, it will also cause deviation and floats. After the above tests and analysis, it is clear that these are not in line with any of the above situations. It seems that all parts of the steering system work well, and there is no bad wear phenomenon.