Table of contents: Signs of a problem with the brake… ↓ Brake lines and hoses ↓ Checking the wear of brake pads and… ↓ Checking the brake booster ↓
Caution: Dust from brake lining wear that accumulates on brake components may contain asbestos, which is hazardous to health. Do not blow out this dust with compressed air or inhale it! Do not use gasoline-based solvents to remove dust.
Note: In addition to checking at specified intervals, the condition of the brake mechanisms should be checked every time the wheels are removed or whenever signs of a malfunction appear in the brake system. Checking the brake fluid level is described in Section 4.
Signs of a problem with the brake system
1. Any of the following symptoms may indicate a potential defect in the brake system:
- When you press the brake pedal while driving, the car "pulls" to the side.
- The brakes make scraping or squealing sounds when braking.
- The brake pedal has excessive travel.
- The brake pedal pulsates (this is normal only when the ABS system is working).
- Brake fluid leaks are observed (usually visible on the inside of a tire or wheel).
2. If you notice any of these signs, inspect the brake system immediately.
Brake lines and hoses
Note: The brake system primarily uses metal brake lines, with the exception of flexible, reinforced hoses near the wheels. Regular inspection of all these lines is essential.
3. Park the car on a level surface.
4. Jack up the car and support it on stands, then remove the wheels. Checking the vacuum hoses is described in Section 5.
5. Check all brake lines and hoses for cracks or abrasions in their outer coating, as well as leaks, bulges and deformations. Check the brake hoses at the front and rear of the vehicle for signs of softening, cracking, deformation, or wear due to friction against other parts. Check all fittings for signs of leaks and ensure that all brake line fasteners are secure.
6. Bend the brake hose in both directions with your hands to identify any damage. The hoses should not be twisted.
7. Turn the steering wheel all the way to the right and left. Make sure that the front brake hoses do not touch any structural elements of the vehicle.
8. If damage to the brake lines or fluid leaks from them are detected, these problems must be corrected immediately. For a more detailed description of the brake system repair procedure, please refer to Chapter 8.
Checking the wear of brake pads and discs
Note: The description of the rejection of ceramic brake discs is given in Chapter 8; the following description regarding brake discs refers to metal discs.
9. Experience shows that due to the presence of dirt on the edge of the road, the wear of the brake pads on the right wheel is greater than on the left. Therefore, it makes sense to check the right wheels.
10. To measure the thickness of the disc brake pads, remove the corresponding wheel and use a caliper (see illustrations).
8.10a/ Thickness of the outer shoe (with a backing) front brake mechanism with the wheel removed.
8.10b. Thickness of the outer shoe of the rear brake mechanism with the wheel installed.
11. Compare the measurement result with the requirements Specifications for Chapter 8 and, if necessary, replace all the brake pads of both wheels of this axle (see Chapter 8).
12. With the wheel removed, check the wheel cylinders of the brake mechanisms for brake fluid leaks. If leaks are detected, repair the wheel cylinders immediately.
13. Visually inspect the brake discs from the inside and outside for grooves, rust and cracks. Replace defective components.
14. Measure the thickness of the brake discs in several places using a micrometer or special calipers. You can also measure the thickness of the brake disc with a regular caliper, placing a lining of a known size on each side of the disc (for example, two coins), and then calculating the difference between the measured value and the thickness of the linings.
15. Compare the minimum of the obtained results with the requirements Specifications for Chapter 8. If the wear limit is reached, replace both brake discs. The brake disc should also be replaced if there are large cracks or deep grooves on the working surface.
Checking the brake booster
16. With the engine off, press the brake pedal several times - with each press its travel should decrease.
17. With the brake pedal depressed, start the engine – the pedal should move down.
18. Keeping the brake pedal depressed, turn off the engine. If the pedal stroke does not change when you hold it down for 30 seconds, the booster is OK.
19. If any of the above checks fail, repair or replace the vacuum booster (see Chapter 8).
(A link to the original source is available on the website «Audimanual.ru»)