09
2026
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05
ABS system failed prematurely, and the culprit turned out to be the dryer tank
When it comes to truck ABS systems, especially trailer ABS systems, many truck drivers would probably complain: 'They're too difficult to use!' Undeniably, the ABS systems installed on many trailers today are indeed uneven in quality, with inferior products flooding the market. However, it should be noted that in many cases, the deteriorating performance of a trailer ABS is not due to the system itself, but because your daily maintenance has not been properly done.
A few days ago, a truck driver from Xinjiang, Brother Hong, purchased several second-hand hazardous materials trailers. While these vehicles were in the hands of the previous owner, the ABS system frequently encountered problems and was modified into a 'brake king' system.
● Rusty and oil-contaminated, the air circuit system was in a terrible state
After Brother Hong took over, he began to restore the functionality of the ABS system. But unexpectedly, as soon as he removed the ABS valve of the original 4S2M system, he discovered very serious problems.
First is its control pipeline interface. It's very obvious that rust has already formed inside. It should be noted that the ABS control valve has very high requirements for the cleanliness of compressed air. If there is moisture in the air circuit, it will corrode iron components, causing rust. This rust will eventually enter the interior of the valve body, causing issues such as the pistons inside the valve body jamming or air leakage.
Secondly, residual oil stains can be clearly seen inside the output port of the brake air pressure, which proves that the truck's air compressor has experienced a severe oil leakage failure—engine lubricating oil has intruded into the air circuit system through the air compressor. There are many rubber seals inside the ABS valve body, and these seals are very sensitive to engine oil. Long-term contact with engine oil can cause the seals to age and deteriorate prematurely, ultimately leading to a decline in ABS system performance.
Since the trailer's ABS valve is located at the far end of the vehicle's air circuit system, it can be inferred that valves closer to the air compressor may be more affected by the engine oil.
After disassembly, it was found that there was even more oil contamination inside the brake master valve, and the entire exhaust port was completely saturated with oil, becoming oily; the air circuit connections were even more exaggerated, with a lot of residual engine oil inside, to the point that it could even flow out.
After the residual engine oil inside the main valve flowed out, it appeared emulsified, which proves that the entire air system was not only contaminated by oil but also mixed with a large amount of water, making it alarming to see.
● Poor maintenance is the culprit, and the repair cost is not small
Why does this happen? Actually, the answer is simple:
First, the truck's air compressor has deteriorated oil sealing performance, causing oil to first enter the dryer.
Second, the previous owner did not replace the dryer in time, causing the dewatering and oil filtering functions to fail, leading to oil and water entering the air system.
For safety and considering the actual condition of the vehicle, truck enthusiast Hong decided to replace all valve bodies, repair the ABS, and replace the dryer with a qualified product; the oil-leaking air compressor will not be touched for now because its oil leakage is not severe. Combined with a qualified dryer, especially one with strong oil removal capability, it can still be used temporarily, only needing a shorter replacement interval for the dryer.
There are no small matters in the braking system. Improper maintenance can be a fatal blow to the precise ABS system. Hopefully, everyone can learn from this lesson and maintain their vehicles regularly. Otherwise, seemingly saving money can actually cost much more and even create serious safety hazards.
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