A 1997 Shanghai Santana GLI sedan, a total of 122,000 km running, the engine idling, steering booster pump issued a "buzzing" sound, when the steering wheel when the left and right when the abnormal noise aggravate. The car replaced two steering booster pumps in a month, replaced the first steering booster pump with about 20 days of noise, and the second one took only seven days. The same problem occurred again. According to maintenance technicians, they purchase channels formal, this accessory has sold more than one, have not had a similar problem.
After demolition of the pump has been replaced, found no abnormal wear and tear. The car parked on a flat road, through a comprehensive visual inspection found that hydraulic lines, pump body and the direction of no oil leakage, the hydraulic oil storage tank between the upper and lower limits, the drive belt is tight and moderate, but the hydraulic oil Black has deterioration (Figure 1). Found through the test, turn the steering wheel left and right, turn normal afterburner, steering steady and flexible in the absence of steering deviation, heavy and floating phenomenon, and the steering back to good.
Is it really caused by abnormal wear and tear of the pump noise? According to the owner to replace the new pump, the lack of oil spill has never been found. This pump is only used less than 10 days, should not be caused by wear and tear inside the pump. If the pump pressure valve and the flow valve is not good, will make the pressure is too low, the performance turned heavy; if the pressure is too high, due to excessive pressure around the power cylinder, driving direction deviation occurs automatically; if the steering distribution Poor valve operation or internal leakage, there will be heavy steering; if the steering valve disturbs the distribution will lead to poor steering back to bit; if the distribution of spool and valve sleeve gap with poor, deviation and drift phenomenon will occur. After the above test and analysis, apparently does not meet any of the above situations, it seems that all parts of the steering system work well, but there is no bad wear and tear.
So far the repair work in trouble, the only exception found in the overhaul of the hydraulic oil is the presence of deteriorating over-dirty phenomenon. The engine idling, turn the steering wheel several times, until the hydraulic oil temperature rose to normal operating temperature (about 80 ℃), spin off the reservoir cover, hold the middle spring by hand, start the engine idling, observe the oil Face, in addition to the discovery of hydraulic oil dirty, also found that the hydraulic fluid in the flow of bubbles from time to time emerge from the surface. Could it be because of bubbles with hydraulic oil flow into the pump, squeezed in the pump and produce aerodynamic noise? If so, then how is the bubble produced? After in-depth analysis, I believe that the cartridge in the reservoir blockage caused the phenomenon.
Why Filter plugging will have such a big noise? Dirty hydraulic oil will filter plug, plug the filter will make the pressure on both sides of the filter is too large, it will make the oil in an unstable state. In the case of a change of oil level, the air is easily mixed into the oil inlet pipe (Figure 2) due to the negative value at the inside, which is transmitted to the pump to be compressed to generate aerodynamic noise.
Replace a steering booster pump filter, and the steering hydraulic system to thoroughly clean, put on the pure standard hydraulic oil, the test found that failure completely ruled out.
In fact, in the Volkswagen series, not only is the filter clogged producing noise, but it also produces aerodynamic noise if the filter is damaged or displaced. This is because the filter cartridge has two functions: one is to filter the sediment and impurities in the system, the other is to eliminate the pulsation when the pressure in the oil return port is too high, so as to prevent air bubbles from being generated so as to make the oil surface calm. Therefore, when the steering booster pump abnormal noise, they should check the filter is clogged, and check the hydraulic oil.
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