Warning! Remember that the dust generated by the brake mechanisms may contain asbestos, which is extremely harmful to human health. Never blow off dust with compressed air or inhale it; wear a protective mask or respirator when servicing the mechanisms. Never use gasoline or petroleum-based solvents to wipe brake system components; use only branded cleaning agents or methyl alcohol! Try to use only asbestos-free components when replacing brake pads.
Note: More detailed illustrative material in Chapter Brake system.
1. The condition of the brake system components, in addition to regular checks specified in the routine maintenance schedule, should be assessed every time the wheels are removed or when signs of malfunctioning of the system occur. Disc brake pads are usually equipped with special indicators that notify of excessive wear of the friction linings with a characteristic squeal when braking. The symptoms listed below may be a sign of a malfunction of the brake components:
- When braking, the car loses directional stability (there is a pull to one side);
- When braking, the brakes make a squealing or squeaking noise;
- The brake pedal travel increases excessively;
- When pressing the brake pedal, pulsations are felt;
- There are traces of brake fluid leakage (usually on the inner surface of wheel rims and tires).
2. Loosen the wheel nuts.
3. Jack up the car and place it on supports.
4. Remove the wheels.
Disc brakes on front and rear wheels
1. The support of each brake mechanism is equipped with two pads, internal and external. The ends of the pads are clearly visible through a special viewing window in the support body (refer to accompanying illustrations) after removing the wheel.
2. The residual thickness of the friction lining of the inner shoe is assessed visually through the above-mentioned inspection window. If the linings are worn beyond the permissible limit (see Specifications), it is necessary to carry out a comprehensive replacement of the brake pads.
Note: Remember that the friction linings are riveted or glued to a metal backing, the thickness of which should not be taken into account when measuring.
3. If it is difficult to visually assess the remaining thickness of the pads, or there is a need for a more detailed inspection of the pads, remove the caliper and take out the pads for a more detailed examination (see chapter Brake system).
4. After the pads have been removed from the caliper, clean them with a special agent and measure the remaining thickness of the linings with a ruler or a caliper with a vernier scale.
5. Use a micrometer to measure the thickness of the brake discs. Compare the measurement results with the standard requirements (see Specifications). If the thickness of any of the discs is outside the permissible range, replace it (see chapter Brake system). If the disk thickness is normal, check its general condition. Pay attention to such defects as deep scratches, grooves, scuffs, traces of overheating, etc., if necessary, remove the disk and have it turned (see chapter Brake system).
6. Before reinstalling the wheels, inspect all brake lines for signs of damage, wear, degradation due to aging of the material, signs of leaks, bends, twists and other deformations (especially near the connection points of flexible brake hoses to the brake calipers) (refer to the accompanying illustration). Check that the hose clamps are securely fastened. Make sure that none of the brake hoses come into contact with sharp corners of adjacent body components, the exhaust system or the suspension (at any steering wheel position). If necessary, make appropriate repairs or adjust the line routing. Replace defective components (see chapter Brake system).
Vacuum booster
1. The proper functioning of the brake booster is checked from the driver's seat.
2. With the foot brake pedal fully depressed, start the engine; the pedal should still fall a little.
3. With the engine running, press the foot brake pedal several times. The pedal travel should remain constant.
4. Press the pedal, turn off the engine and continue to hold the pedal pressed for about another 30 seconds, during which time it should neither fall lower nor rise.
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5. Start the engine again, let it run for a minute, then turn it off again. Press the pedal firmly again several times – the stroke should decrease with each stroke.
6. If the result of the described check is negative, the brake booster servo drive is subject to repair or replacement (see chapter Brake system).
Parking brake
1. Slowly pull the parking brake control lever up to the end of its travel and count the number of clicks of the ratchet. Compare the count with the requirements Specifications. If necessary, make the appropriate adjustments (see chapter Brake system).
2. Alternatively, the parking brake can be checked for proper operation by parking the vehicle on a downhill section of the road and holding it still with the parking brake with the gearbox in neutral. If the brake does not hold the vehicle when the lever is pulled the required number of clicks, adjustments must be made.