3.12. Check of components of the brake system
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The dust which is formed as a result of wear of frictional slips and accumulating on a surface of components of brake mechanisms may contain asbestos hazardous to health. Do not blow off dust compressed air and do not inhale it! Do not use for rubbing of components of the brake system solvents on the basis of gasoline! |
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Besides the regular procedures stipulated by the Schedule of routine maintenance (see the Section Schedule of Routine Maintenance), a condition of brake mechanisms it is necessary to check every time at removal of wheels or at emergence of signs of violation of serviceability of functioning of the brake system. |
Signs of malfunctions in the brake system
Blocks of disk brake mechanisms are usually equipped with the special indicators notifying on excessive wear of frictional slips characteristic squeal when braking.
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At identification of the fact of contact of indicators with brake disks of a block have to be replaced immediately! |
Any of the listed below signs can indicate potential defect of the brake system:
- When braking the car loses course stability (there is a withdrawal in one of the parties);
- During braking brake mechanisms publish squeal or a scratch;
- Excessively the course of a pedal of a foot brake increases;
- When squeezing a brake pedal the pulsations which are not connected with ABS operation are felt;
- Are observed leak of brake fluid (usually on the internal surface of wheel assemblies).
In case of detection at least of one of these signs immediately examine the brake system.
Brake lines and hoses
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In the brake system steel brake tubes, except for the flexible reinforced hoses at forward wheels and as connections at the back bridge are generally used. Regular survey of all these lines is very important. |
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- Tire out the car on a platform / a viewing hole, or a poddomkratta it and hang out on props. Remove wheels.
- Attentively examine all brake lines and hoses on existence of signs of damages, wear, destruction as a result of aging of material, traces of leaks, bends, twisting and other deformations, the person paying attention to places of connection of flexible hoses to supports / to wheel cylinders of brake mechanisms. Estimate reliability of tightening of all fixture, including homutny and nipple connections.
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In case of need use a mirror. |
- Bending hose sections of brake lines make sure of lack of signs of their hidden damages.
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It is not necessary to twist hoses. |
- Turning a steering wheel from an emphasis against the stop, make sure that hoses at the same time do not touch elements of a design of the chassis/suspension bracket/helmsman of drive/system of release, - in case of need make the corresponding corrections, or correct a route of laying of lines. Replace defective components (see the Head the Brake system).
- Study on existence of signs of development of leaks/corrosion and mechanical damages of a surface of GTTs, wheel cylinders and the valve regulator of pressure. Replace defective components.
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Disk brake mechanisms
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Replacement of brake shoes should be made in a set for both wheels of a forward axis of the car! |
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The support of each of brake mechanisms is equipped with two blocks, - internal and external. End faces of blocks are well looked through through special observation ports in the support case after removal of a wheel. |
Assessment of residual thickness of blocks is made visually through the observation ports mentioned above. If frictional slips are worn-out over an admissible limit (see Specifications to the Head the Brake system), it is necessary to make complex replacement of brake shoes.
If visually to estimate the residual thickness of blocks it appears difficult, or there is a need for more detailed survey of blocks, remove a support(s) and take blocks for more detailed studying (see the Head the Brake system).
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- After blocks are taken from a support, clear them by means of special means and measure the residual thickness of slips by means of a ruler or a caliper.
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- Measure by a micrometer thickness of brake disks, then by means of the dial measuring instrument (DTI) determine the size of their side beating. Compare results of measurements to standard requirements (see Specifications of the Head the Current leaving and service). If thickness or size of a side beating any of disks leaves abroad admissible range, replace it (see the Head the Brake system). If thickness of a disk is normal, estimate its general condition. Pay attention to such defects as deep scratches, furrows, teases, overheat traces, etc., in case of need remove a disk (see the Head the Brake system) and send him to a pro-point. The worn-out or deformed spring clamps of blocks are also subject to replacement.
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Drum brake mechanisms
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Replacement of brake boots should be made in a set for both wheels of a back axis of the car! |
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- Remove brake drums (see the Head the Brake system).
- Make careful cleaning of brake mechanisms with use of the special cleaning structure.
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Do not blow off brake dust from a surface of components compressed air at all and do not inhale it - dust may contain asbestos, harmful to your health! |
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- Estimate the residual thickness of frictional overlays of forward and back brake boots, check components for existence of traces of pollution by brake fluid and oil. If the frictional slip acts over heads of rivets less than on 1.6 mm, boots are subject to replacement in a set for brake mechanisms of both wheels (see the Head the Brake system). Boots should be replaced also in case of identification of cracks, zapolirovanny to gloss of sites of slips, or traces of hit of brake fluid.
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- Make sure of correctness of connection and serviceability of a condition of all springs of assembly of the brake mechanism (see the Head the Brake system), - the neglect replacement of the deformed or weakened springs is fraught with premature wear of boots as a result of "prikhvatyvaniye" of brakes.
- Check assembly components for existence of traces of leak of brake fluid. Having carefully hooked a finger or the small screw-driver, remove rubber boots from the wheel cylinder which is holding apart the top ends of boots. Identification of any signs of leaks in these parts demands carrying out immediate recovery repair of assembly of the cylinder (see the Head the Brake system). Also check brake hoses and their nipple connections for existence of traces of leaks.
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- Carefully wipe the internal surfaces of the reel with the pure rags impregnated with methyl alcohol, - try not to inhale brake dust. Examine the working surface of the reel on existence of cracks, zadir, traces of an overheat and other damages. If defects cannot be removed by processing of a surface with a fine-grained emery paper, the drum should be given for a pro-point to a workshop of car service, or to replace (see the Head the Brake system). Measure the internal diameter of a drum. In case of need measure diameter of the boots put in brake assembly (see in the same place), then, by subtraction of result of the second measurement from result of the first, determine the size of a working gap of the brake mechanism.
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- Repeat the procedure for components of the opposite brake mechanism. Install into place reels, fix wheels and lower the car on the earth. Tighten wheel nuts with the required effort.
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Check of the parking brake
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- Park the car on the flat horizontal platform, transfer РКПП/АТ/раздаточную коробку to neutral situation and release the parking brake, - the car has to move manually without resistance caused by operation of back brake mechanisms.
- Cock the lever of the parking brake on 1 click and repeat check, - the car should not move.
- Completely cock the lever of the parking brake: the maximum admissible length of the course of the lever should not exceed 10 clicks of a ratchet, otherwise adjust the parking brake (see the Head the Brake system).
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