Volkswagen steering booster pump has abnormal symptoms
A 1997 Shanghai Santana GLI sedan with a total of 122,000 km on the odometer has been experiencing an unusual humming noise from the power steering pump. The sound becomes more noticeable when turning the steering wheel left or right. The vehicle owner replaced the power steering pump twice within a month—first after about 20 days, and then again just seven days later—but the same issue persisted. According to the mechanic, the parts were purchased through official channels, and there have been no similar complaints from other customers who have used the same component.
After removing the old pump, no signs of abnormal wear were found. The car was parked on a flat surface, and a thorough visual inspection revealed no oil leaks in the hydraulic lines, pump body, or steering gear. The hydraulic fluid level was within normal limits, the drive belt was properly tightened, and the fluid appeared black but not visibly contaminated. During testing, the steering turned smoothly without any heavy, floating, or drifting issues, and the return-to-center function worked well.
The question remains: was the noise caused by internal wear in the pump? The owner mentioned that there was no oil leakage, and since the pump had only been used for less than 10 days, it’s unlikely to be due to mechanical wear. If the pressure relief valve or flow control valve was faulty, it could cause heavy steering or automatic drift. A malfunctioning distribution valve might lead to poor return-to-center performance or internal leakage, resulting in stiff steering. However, all tests showed that the system operated normally, with no signs of damage or wear.
At this point, the only anomaly found during the overhaul was the deteriorated condition of the hydraulic oil. When the engine was idling and the steering wheel was turned several times, the oil temperature reached around 80°C. After removing the reservoir cap, the mechanic noticed that the oil was dirty and occasionally bubbled up from the surface. Could these bubbles be causing aerodynamic noise inside the pump?
Further investigation suggested that the issue stemmed from a clogged filter. When the filter becomes blocked, it creates excessive pressure differential across it, leading to unstable oil flow. This can cause air to be drawn into the system, which then gets compressed in the pump, creating the buzzing sound.
Replacing the filter and thoroughly cleaning the hydraulic system, followed by refilling with clean, standard hydraulic fluid, completely resolved the issue.
In Volkswagen models, a damaged or misaligned filter can also cause similar noises. The filter serves two main purposes: filtering contaminants and reducing pressure pulsations in the return line, which helps prevent air bubbles from forming. Therefore, whenever a power steering pump makes strange noises, checking the filter and the condition of the hydraulic fluid should be a top priority.
GUANGDONG YONGLONG ALUMINUM CO.,LTD , https://www.yonglongaluminium.com