A 1997 annual production Santana GLI sedan, the cumulative driving 12.2 million km, the engine in the idle operation, the steering pump to send a "buzzing" sound, when the left and right turn the steering wheel when the abnormal increase. The car in a month to replace the two steering pump, put the first steering pump to use when the use of about 20 days of noise will appear, the first two only 7 days the same problem will appear again. According to the maintenance of technical personnel, they purchase channels of formal, this accessories have sold more than one, have not appeared similar problems.
    After the demolition of the pump has been changed, no abnormal wear. The car stopped at the flat road, through a comprehensive visual inspection found that hydraulic piping, pump and the direction of the machine without oil leakage phenomenon, the tank of hydraulic oil between the upper and lower limits, the belt elastic moderate, but the hydraulic oil Black is a deterioration of the phenomenon. Through the test found, turn around the steering wheel, steering force normal, in the steering to the stable and flexible, did not appear when the steering deviation, heavy and hair floating phenomenon, and turned back to good.
    Is it really a noise generated by abnormal wear in the pump? According to the owner to put on a new pump, never found the phenomenon of oil spill. And this pump only used less than 10 days, should not be due to wear within the pump. If the pressure inside the pump pressure valve is too poor, the pressure will be too low, the performance of the steering heavy; if the pressure is too high, because the power cylinder left and right pressure is too large, driving will appear in the direction of automatic deviation; if the steering distribution The valve is poor or internal leakage, there will be heavy steering; if the steering distribution valve stuck, will lead to poor return position; if the distribution of spool and valve sleeve with poor clearance, there will be deviation and hair phenomenon. After the above test and analysis, apparently does not meet any of the above conditions, it seems that the various parts of the system work well, there is no adverse wear and tear phenomenon.
    At this point the repair work is in trouble, the only anomaly found in the maintenance is that there is deterioration of the hydraulic oil dirty phenomenon. So that the engine idling operation, turn the steering wheel several times, until the hydraulic oil temperature rose to normal operating temperature (about 80 ℃ or so), unscrew the tank cover, hand hold the middle spring, start the engine idling operation, Surface, in addition to the discovery of hydraulic oil is dirty, but also found that hydraulic oil in the course of the flow of bubbles from time to time out of the liquid surface. Could it be because the bubble with the flow of hydraulic oil into the pump, squeezed in the pump and produce aerodynamic noise? If so, how does the bubble come about? After in-depth analysis, maintenance personnel that is the storage tank cylinder blockage caused by the above phenomenon.
    Why the filter block will produce such a big noise? Hydraulic oil dirt will make the filter blockage, filter blockage, will make the filter inside and outside the pressure difference is too large, so the oil will be in an unstable state. In the case of oil changes, because the inside is too large negative, it is easy to mix the air into the tubing, the pump is squeezed to produce aerodynamic noise.
    Replace a steering pump pump, and turn the hydraulic system to thoroughly clean, put the pure standard hydraulic oil, test the fault found completely ruled out.
    In fact, in the Volkswagen series models, not only the filter block will produce noise, if the filter is damaged or shift will produce aerodynamic noise. This is because the filter has two roles: one is the sedimentation system within the sediment and impurities, and second, when the oil pressure is too high, play to eliminate the role of pulsation, to prevent the bubble, so that the oil surface calm. Therefore, when the steering pump appears abnormal sound, you should see whether the filter is blocked, and the hydraulic oil to check.