Solving brake maintenance problems, wishing all truck drivers a safe journey home

Experienced drivers who are on the road all year round know that the maintenance of the brake system is crucial for the safety of driving a car. The car's brake system is generally divided into two types: one is called hydraulic brakes, and the other is called air brakes. Since the braking structures and working principles of the two are different, the methods for brake maintenance are also very different.

▎Hydraulic Brake

Hydraulic brakes have a simple structure and small size. They only require a brake master cylinder, wheel cylinders, a brake fluid reservoir, and connecting pipes, without needing other auxiliary equipment. Hydraulic brakes are characterized by slightly slower response, smooth braking, and lower braking force, so they are generally used in light trucks.

Principle of hydraulic braking: When we press the brake pedal, the force is transmitted to the brake master cylinder. The master cylinder is like a syringe filled with brake fluid. When the force is applied, the piston pushes the brake fluid forward. The brake fluid flows through the brake lines to the wheel cylinders at the four wheels. The wheel cylinders then push the brake pads, clamping the brake discs to achieve braking.

For cars with hydraulic brakes, check the brake fluid level before driving. If the fluid level is found to be low, immediately inspect the brake lines for leaks. Since brake fluid absorbs moisture from the air, it becomes ineffective over time, so it is best to replace it once a year.

▎Air Brakes

Compared to the structure of hydraulic brakes, air brakes are much more complex. In addition to the master cylinder, wheel cylinders, and brake lines, they also include an air compressor (connected to the engine via a belt), air tanks, a high-pressure controller (to regulate pressure, which can reach 8 atmospheres for vehicles), relay valves, and other components. They require a large installation space and have a more complicated structure. Moreover, to ensure safety, the rear brake wheel cylinders are now all air-interrupted brakes (increasing cost and structural complexity). Additionally, since air brakes respond quickly, are abrupt, and exert strong force (with air pressure up to 8 atmospheres), they are mostly used on large trucks and buses.

Pneumatic Brake Principle: When we press the brake, it is equivalent to opening the master pump valve (both are check valves, allowing air in but not returning). Compressed air passes through the check valve into the rear brake spring cylinder, pushing the brake arm, which rotates the brake cam, expanding the brake shoes (mostly now made of asbestos with copper wire) to press tightly against the brake drum (cast iron), achieving the braking effect. Nowadays, dual-circuit and cross-brake pipeline systems are used to ensure that even if there is a leak in one part of the pipeline, braking can still occur.

● Inspection and Replacement of Brake Pads and Brake Discs

For trucks, especially when loaded, the mass is large, and inertia is also large, so the force on the brake pads during braking is greater, generating more heat. Most brake failures are caused by the continuous heating of brake pads during operation, making the maintenance of the brake pads and brake discs extremely important.

Brake pads and brake discs are wear parts, and their wear level is related to the driver's braking habits and the driving conditions. You can judge this by observing the wear of the truck's brake pads; if it reaches a critical point, they need to be replaced immediately. The main maintenance for brake pads includes high-temperature protection of the pads, lubrication and maintenance of the brake caliper pistons, and cleaning of the brake discs.

Uneven Brake Pad Wear  

Like brake pads, brake discs also need to be replaced only when they have worn to the limit. Generally, when replacing three sets of brake pads, the brake discs should also be replaced. After frequent use, brake discs generate high temperatures due to friction, and in severe cases, they can even be burned to a brick-red color. At this point, some drivers might consider cooling them with water, but this actually causes significant damage to the brake discs.  

● Inferior Drying Tanks Pose Serious Risks — Must Avoid!  

Everyone is familiar with drying tanks, which are used to filter water vapor in the compressed air system, preventing corrosion in air tanks and various pumps and valves. Therefore, whether a drying tank functions properly directly affects braking performance. Drying tanks are not expensive, but many truck drivers try to save money whenever possible and don't really care about the quality of the tank, as long as one works. Some don’t replace them for several years.

Dryer installed on the air circuit

Some truck drivers, tempted by cheap prices, can easily fall into the trap of counterfeit dryers. Currently, the price of genuine dryers on the market is generally around 200 yuan, while the retail price of inferior products is usually below 100 yuan, and even the wholesale price can be only 20 to 30 yuan. After using such low-quality dryers for a short period of time, they lose their ability to absorb moisture from the air, and some desiccant inside the dryer can even enter the vehicle's air circuit system, causing greater safety and property losses. Previously, a truck driver shared his personal experience: once while driving to Heilongjiang, the brake caliper froze due to water ingress caused by a failed low-quality dryer, resulting in brake failure. In the cold winter weather, choosing a high-quality dryer has become quite a science.

Fake 'Relative' Drying Canister

Additionally, when we choose a drying canister, we should try to select those with fine and numerous vent holes and a stronger structure. Many drying canisters on the market use vent holes with relatively large diameters. This design may not seem problematic at first glance, but if thinner filter paper and smaller diameter desiccants are used, it is easy for the larger pressure in the vehicle's air line to push the internal desiccant out, directly entering the vehicle's air line, causing blockages and creating safety hazards.

The lifespan of the drying canister is highly related to its usage environment. Generally speaking, when the air canister farthest from the air compressor starts to release water, it indicates that the drying canister is tending to fail and should be replaced immediately.

● Water in the Air Line During Winter: How to Avoid It?

In winter, various braking problems arise one after another, and air line issues are often the most overlooked by many truck drivers. Much of the air heated after passing through the air pump and gradually cooling while continuing through the tubes will condense moisture from the air into liquid due to the cooling process. Therefore, when there is moisture in the air lines during winter, many issues can occur. In this case, the drying canister becomes even more important. If the drying canister fails, excessive moisture in the air lines can freeze and block the lines, causing the brakes to be unresponsive or even fail, potentially leading to accidents.

From another perspective, in winter, the dry and cold conditions make many air pipelines very fragile, prone to cracking or even breaking. Once there is an air leak, the air pressure in the system cannot reach the set value, causing brake failure and also preventing the drying tank from regenerating.

Therefore, before driving, carefully check whether the air line connectors are aged or cracked, and if any issues are found, replace them promptly. Next, always keep an air hose and quick couplings in the vehicle; in case the air line breaks, they can be replaced and repaired immediately. Since the air lines are distributed over a wide area, they inevitably come into contact with the chassis or other parts. If the contact points experience frequent friction, the lines will wear out faster, so it is necessary to regularly inspect and wrap areas where the lines are dispersed to prevent accelerated damage.  

● The air pump, often overlooked, holds profound knowledge  

The air pump is the source of air pressure for the entire vehicle, with the most important use being for the brakes. In routine maintenance, the air pump is also one of the easily neglected areas. If not properly maintained, the air pump can suffer abnormal wear, oil leakage, and oil consumption, potentially causing water or oil to enter the air lines, which affects the vehicle’s braking performance.

Nowadays, air compressors basically take air from the intake duct, then compress it into the air storage tank. When using low-quality air filters or allowing the compressor's intake duct to operate alone, debris can easily enter the compressor, causing abnormal wear. Abnormal wear on the compressor mainly occurs on the cylinder, piston rings, and the bearings of the compressor's rotating shaft.

Long-term intake of impure air can lead to severe cylinder wear, increased diameter, thinning of the piston rings, and inadequate lubrication by engine oil, among other issues. More severe cases can cause oil passing through the compressor, where engine oil enters the air storage tank due to compression, thereby affecting brake performance and also consuming engine oil.

Scale build-up inside the air pump

Some air pumps use engine circulating water for cooling, similar to the engine block. Some truck owners, in their daily use, replace antifreeze with water, causing scale to form inside the air pump, blocking the water passages and affecting the pump's heat dissipation. Therefore, for air pump maintenance, it is recommended that truck owners use high-quality air filters and antifreeze, and not let the air pump intake pipe operate independently.

During driving, the normal operation of the braking system is extremely important. Once it fails, the safety of the truck owners is threatened. Therefore, truck owners must pay extra attention to brake maintenance! With the New Year approaching, we hope that every truck owner on the road can return home safely to reunite with their wife and children.