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2026
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Comprehensive Analysis of Air Brake Failures: Knowledge Every Truck Driver Must Learn!
As temperatures begin to rise, common faults in air brake systems include not building air pressure, brakes not returning, and brake failure. Although these issues have gradually decreased, even a slight oversight can lead to serious accidents. Therefore, it is very important to conduct a comprehensive inspection of the vehicle's air brake system. The basic structure of mainstream domestic truck air brake systems has not changed much over the years despite improvements and upgrades, but new components like ABS sensors and air dryers place higher demands on the braking system, which also requires special attention.
Through investigations with truck owners and some accident cases, some serious accidents, such as trailer fires and brake failures, are all related to the braking system. Some faults are caused by the system not being inspected regularly or using counterfeit parts. Since these parts may appear intact at the time, they can easily create a false impression.
The following aspects illustrate several key points for inspection and regular replacement of parts.
1. Air Compressor Inspection – Severe Oil Leakage Can Lead to Downstream Failures
When regularly checking the exhaust port of the pressure relief valve, pay attention to whether the oil contamination is severe. If the oil contamination is serious, the air compressor needs to be repaired, and if necessary, replaced.
Check the pressure relief valve exhaust port.
Pay special attention to whether the air compressor's lubricating oil pipe is intact. Note that the oil pipe cannot be repaired by welding before installation. Check for any misalignment or vibration during installation. A broken lubricating oil pipe can easily cause serious damage to the air pump and engine. The vehicle should carry a spare oil pipe for replacement when necessary.
Pay attention to checking the oil lubrication pipes of the air compressor.
During cold starts in winter, before the water temperature reaches 60-80 degrees, it is strictly forbidden to run the engine at high throttle, to prevent poor lubrication of the air compressor, which can cause cylinder scuffing and excessive wear, leading to oil leakage and carbon buildup on the cylinder head (air compressor).
2. Dryer Inspection: High intake air temperature affects regeneration performance
It is difficult to judge the performance of a dryer from its appearance. Since a dryer completes a work cycle, it requires two actions: 'absorbing water - draining water'.
Dryer Inspection
In addition to choosing a high-quality dryer, it is necessary to check whether the system is working normally. For example, if there is severe oil contamination under the exhaust port, it indicates that the dryer's molecular sieve is heavily contaminated by oil and has completely failed, losing its water-absorbing function.
Intake Temperature End Inspection
The intake temperature end inspection can be completed using temperature-sensitive paper. When the temperature exceeds 65 degrees, the performance of the dryer filter decreases or even fails.
3. Brake Return Inspection – Pay Attention to Active and Passive Return
① Active Return Part
The active return action is affected by multiple components. First, when there is sufficient compressed air, press the brake pedal and quickly release it. Observe the exhaust condition of the relay valve or quick-release valve. If the exhaust is slow, timely maintenance and replacement are required.
Pay attention to the exhaust status of the relay valve and quick-release valve.
Most valve body damage is related to oil contamination and water ingress, so check the dryer.
② Passive return parts
The passive return parts refer to various components inside the brake drum. The return springs of the brake shoes need to be checked by prying up and down with a lever. If they lack elasticity or are fatigued and elongated, they need to be replaced in time.
Return spring for brake shoe
To prevent the lower brake shoe from returning poorly over a long period, which can cause interference and friction with the brake drum, leading to high temperatures, and creating a false sense of tightness when adjusting the brake shoe clearance, making correct adjustment impossible.
4. Brake Shoe and Drum Inspection: Pay attention to the lifespan of the brake drum
The quality of the brake shoes, which is often overlooked, also affects braking performance. Counterfeit BPW axle brake shoes cannot achieve 40% of the friction of genuine factory shoes, leading to overheating and premature brake drum failure. Riveting the brake shoes requires specialized equipment; manual riveting or using bolts can easily come loose.
Brake pad quality should be chosen carefully.
After long-term use of the brake hub, the edges may develop a 'mossy' appearance, which is normal. If the main body of the brake hub has no cracks and the inside is smooth, it can be repaired and used normally within a 3MM range. Flatten the excess grooves with a grinding wheel, and replacing with thicker brake pads can allow continued use, saving economic costs.
When the inner diameter of the brake hub wears larger, using a "camshaft with enlarged rollers" method can restore braking power. It should be noted that after replacing with enlarged rollers, the curve of the braking action also changes, which can easily result in poor return, especially when the gap between brake pads is too large.
Adjustment of Brake Clearance
Normally, it is necessary to adjust the brake clearance in a timely manner. At this time, the return spring of the brake shoes has limited effect, and the return spring of the wheel cylinder needs to be strengthened.
Summary: Counterfeit parts such as modified valves, inferior brake pipes, and dryers can be very harmful. There is no profound theory, only essential knowledge to be learned. The careful and meticulous spirit of the older generation is still useful; remember this.
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