Warning! 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. Dust should be washed off with a special brake system cleaner or methyl alcohol in a drain container. After wiping brake system components with a damp cloth, keep the cloth and the contents of the drain container in a closed and labeled container. In the future, if possible, try to use asbestos-free components.
Note. In addition to checks at regular intervals, the condition of the brake mechanisms should be carried out each time the wheels are removed or when signs of a malfunction appear in the system. To ensure driving safety, the brake check procedures described below are the most important of all vehicle maintenance procedures you perform.
Signs of problems in the brake system
Disc brakes may have built-in lining wear indicators that indicate when lining wear has reached a critical level. In this case, the pads should be changed immediately, otherwise the brake discs will be damaged and they will require costly repairs.
Any of the following symptoms may indicate a potential defect in the brake system:
- When depressing the brake pedal, the car «leads away» one way
- Brakes make screeching or squealing noises when braking
- Brake pedal has excessive travel
- Brake pedal pulsing (this is normal only when the ABS system is working)
- Brake fluid leaks (usually 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
Note. The brake system mainly uses steel brake pipes, with the exception of flexible reinforced hoses at the front wheels and as connections at the rear axle. Regular inspection of all these lines is very important.
1. Park your vehicle on level ground and turn off the engine. Remove wheel covers. Loosen but do not remove all four wheel bolts.
2. Jack up the vehicle and place it securely on jack stands.
3. Remove the wheels (see Section Jacking and towing or Owner's Manual for your vehicle).
4. Check all brake lines and hoses for cracks and abrasions in their outer coating, 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 components. Check all fittings for signs of leaks and make sure all bolts and brake hose clamps are secure.
5. If fluid leaks or damage is found, repair them immediately. For a more detailed description of the procedure for repairing the brake system, refer to Chapter Brake system.
Disc brakes
1. If not already done, jack up the vehicle and place it securely on jack stands.
2. You can now see the disc brake calipers with the pads inside. Each caliper has outer and inner pads - both should be checked.
3. Estimate the thickness of the pads by looking into the inspection hole in the caliper body. If the thickness of the friction linings is 2.0 mm or less, or if they are worn more on one side than on the other, then the pads should be replaced (see chapter Brake system). Remember that friction linings are usually glued to the pad's metal backing - its thickness should not be taken into account in the measurement. Always replace pads on both sides of the vehicle (complete on one axle), even if only one of them is worn out, otherwise the braking process will be uneven.
4. Look into the special inspection hole in the caliper to check the brake pads - brake pads that rub against the disc can also be checked by looking through the ends of the caliper.
5. Remove the calipers without disconnecting the brake hoses (see chapter Brake system).
6. Check the condition of the brake disc. Inspect it for gouges, deep scratches, and hot spots (they look like blue or discolored spots). If signs of damage or wear are found, the disc can be removed and machined in a machine shop; if this is not possible, it should be replaced. In both cases, both discs should be replaced or machined, even if only one of them is worn out. In more detail, the inspection and repair procedure is described in Chapter Brake system.
Drum brakes
1. Using the instructions of the Chapter Brake system, remove the rear brake drums.
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 2.0 mm of the rivet heads or metal base, replace the 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.
If the pads are glued to the backing of the shoe, their thickness is measured from the surface of the backing, as shown in the figure (A); if the linings are riveted to the metal of the shoe, the measurement is made from the surface of the lining to the tops of the rivet heads.
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 (see chapter Brake system).
5. Check the drums for deep scratches, crack grooves, and overheated areas that look like discolored spots. If the identified defects cannot be eliminated with sandpaper, the drum should be machined in the workshop (see chapter Brake system for more details).
6. Following the instructions of the Chapter Brake system, install the brake drums.
7. Install the wheels, but do not lower the vehicle yet.
Parking brake
The simplest, and perhaps most obvious, way to test the parking brake is to park the vehicle on a steep hill with the brakes engaged and the transmission in neutral (You must be in the car during the check). If the parking brake keeps the car from rolling, it should be adjusted as described in Chapter Brake system.