Dust resulting from wear on the linings and accumulating on brake components may contain asbestos that is hazardous to health. Do not blow this dust out with compressed air or inhale it! Do not use gasoline-based solvents to remove dust.
In addition to checks at regular intervals, the condition of the brake mechanisms should be carried out each time the wheels are removed or if signs of a malfunction appear in the brake system. Checking the brake fluid level is described in Section Checking fluid levels, leak control.
Signs of problems in the brake system
Any of the following symptoms may indicate a potential defect in the brake system:
- When depressing the brake pedal while the vehicle is moving "leads away" one way;
- Brake mechanisms during braking make scraping or squealing sounds;
- The brake pedal has excessive travel;
- Brake pedal pulsing (this is normal only when the ABS system is working);
- Brake fluid leaks (usually visible on the inside of a tire or wheel)
If at least one of these signs is found, inspect the brake system immediately.
Brake lines and hoses
The brake system mainly uses metal brake pipes, with the exception of flexible reinforced hoses at the wheels. Regular inspection of all these lines is very important.
1. Park your vehicle on level ground.
2. Jack up the car and place it on jack stands, then remove the wheels. Checking vacuum hoses is described in Section Checking the condition and replacing hoses and tubes in the engine compartment, localizing leaks.
3. Check all brake lines and hoses for cracks and abrasions in their outer coating, as well as leaks, swelling and deformation. Check the brake hoses at the front and rear of the vehicle for signs of softening, cracking, deformation, or wear due to rubbing against other parts. Check all fittings for signs of leaks and make sure all brake line fasteners are secure.
4. Bend the brake hose back and forth with your hands to check for damage. Hoses should not be twisted.
5. Turn a steering wheel to the right and to the left against the stop. Make sure that the hoses do not touch the vehicle structure.
6. If fluid leaks from the brake lines or damage are found, the leaks should be repaired immediately. For a more detailed description of the procedure for repairing the brake system, refer to Chapter Brake system.
Checking the thickness of brake pads and discs
Disc brakes
1. Jack up and jack up the vehicle, then remove the appropriate wheel.
Experience shows that due to the presence of dirt on the edge of the road, the wear of the brake pads of the right wheel is greater than that of the left. Therefore, to check it makes sense to remove the front right wheel.
2. Measurement of the thickness of the disc brake pad is made through a special control window in the caliper. If the pad friction lining thickness is less than 3 mm, replace all pads on both wheel brakes for that axle (see chapter Brake system).
As a rule, 1 mm of brake pad wear corresponds to at least 1000 km of run under adverse operating conditions. Under normal conditions, the pads are erased much more slowly.
3. Check brake calipers for leaks. If leaks are found, repair the caliper immediately.
4. Visually check the brake discs on the inside and outside for gouges, rust and cracks. Replace defective components.
5. Measure the thickness of the brake discs in several places using a micrometer or a special caliper. You can also measure the thickness of the brake disc with a conventional caliper by placing a pad of known size on each side of it (e.g. two coins), and then subtracting the thickness of the pads from the measured value.
6. Compare the minimum of the obtained results with the requirements of the Specifications for the Chapter Brake system. If the wear limit is reached, be sure to replace both brake discs. The brake disc should also be replaced if there are large cracks or deep grooves on the running surface.
Parking brake shoes
1. Using the instructions of the Chapter Brake system, remove the rear brake discs.
2. Measure the thickness of the friction linings on the rear brake shoes and inspect them for signs of contamination with brake fluid or grease. If the pad is within 1.5mm above the rivet heads or metal base at its thinnest point, replace all shoes. Cracked, polished to a shine and contaminated with brake fluid or grease should also be replaced. The replacement procedure is described in Chapter Brake system.
3. Check up a condition of coupling and retaining springs of boots, and also the adjusting mechanism. Make sure all of these components are properly installed and in working order. Worn or deformed springs can cause premature friction lining wear.
4. Check the wheel cylinders for signs of leaks by gently pushing back the protective rubber boots. The presence of slight traces of moisture under the covers is allowed. If brake fluid is found under them or it flows out of the wheel cylinder, then the cylinders should be overhauled or replaced (contact the head Brake system).
5. Check the drums for deep scratches, gouges, cracks, and hot spots that look like discolored spots. If the identified defects cannot be eliminated with sandpaper, the drum should be machined in the workshop.
6. Following the instructions of the Chapter Brake system, install the brake discs.
7. Install wheels. If a parking brake test is required, do not lower the vehicle to the ground.
Checking the reliability and travel of the parking brake lever
1. The easiest way to check the operation of the parking brake is to park the vehicle on a steep hill with the brake engaged and the transmission in neutral (must be in the vehicle during the check). If the parking brake does not keep the vehicle from rolling, it should be adjusted (see chapter Brake system).
2. Jack up the back of the car and place it on stands.
At a speed of 40 km/h, it is first recommended to carefully apply the parking brake until you feel light braking. Then, while maintaining the indicated speed, cock the lever one more click and drive for about 400 m. After that, release the parking brake and let it cool.
3. Set the parking brake 5 teeth. Turn the wheels by hand - you should feel a slight resistance from the brake action.
4. Tighten the brake 6 teeth. The wheels must not be turned by hand. If the lever needs to be cocked further to create braking, adjust the parking brake (see chapter Brake system).
Checking the vacuum brake booster
1. With the engine off, depress the brake pedal several times - with each press, its stroke should decrease.
2. With the brake pedal depressed, start the engine - the pedal should go down.
3. Keeping the brake pedal depressed, stop the engine. If the pedal stroke does not change when holding the pedal for 30 seconds, the vacuum booster is in order.
4. If one of the above checks fails, repair or replace the vacuum booster (see chapter Brake system).