9.10.3. Replacement of front brake shoes
Only use original or company (for example, ATE) spare parts can guarantee preservation of the required brake way, service life of these details, and also lack of scratches. Overlays of blocks are produced with various degree of hardness. For example, for cars of a taxi firmer as service life, than optimum braking from high speed is more important at small effort to pedals are used. Blocks for sports cars, on the contrary, softer. Mercedes during numerous tests especially for this car developed an optimum ratio between service life and level of comfort when braking. At each replacement of blocks it is necessary to consider the following:
1. It is necessary to replace all four blocks of one axis that efficiency of braking remained uniform.
2. It is necessary to check wear and a condition of brake disks. They should not have scratches or deep рисок (see. "Replacement of brake disks").
3. It is necessary to check a condition of a protective boot, and also how freely the piston moves in the brake cylinder.
4. At the removed brake shoes do not press a brake pedal at all, otherwise pistons of brake cylinders will leave the openings.
SEQUENCE OF WORKS
1. Install the car on support and fix it. Remove a forward wheel.
2. A hand extend a support bracket outside for what press the brake piston into an opening a little.
3. The screw-driver hook a plastic cover of the socket of the sensor of wear of blocks. Uncover and take out the socket.
4. Wring out the screw-driver the holding bracket from a support.
5. Remove the screw-driver protective caps from the directing fingers.
Fig. 8.13. Use of an internal six-sided key for easing and an otvorachivaniye of the directing fingers from support
6. Twist the directing fingers (fig. 8.13) from the top and lower support of a support, holding Rozhkov a key six-sided vents about a rubber cover.
7. Remove a support and suspend it on a wire so that the brake hose was not extended.
Fig. 8.14. The internal block is established on the piston of a support (shooter) through a returnable spring. Thus, at a brake pedal otpuskaniye the brake disk receives a free wheeling again
Fig. 8.15. Replacement of front brake shoes: 1 – a support bracket (it is removed and suspended on a wire); 2 – external brake shoe; 3 – an internal brake shoe (brake shoes are removed from an arm, on an internal block the wear sensor is installed)
8. Remove an internal block from the brake piston (fig. 8.14). It is fixed by the holding bracket (fig. 8.15).
9. Remove the wear sensor from an internal block.
10. Remove an external block from an arm.
Fig. 8.16. After long operation of a detail of a support and guides of blocks become covered with brake dust. For correct work before installation of new blocks clear an arm and a support a metal brush
11. Before assembly clear support details a brush with a soft metal bristle (fig. 8.16) or the rag moistened with alcohol. Do not use mineral solvents or the tool with keen edges. Deposits of brake dust and corrosion on details of a support can result in uneven wear of blocks.
12. Check a condition of an antisplash cover of the brake piston. At detection of damages replace it as penetration of dirt will quickly lead to jamming of the piston.
Fig. 8.17. Cave-in of the piston of the brake mechanism in the cylinder by means of a clamp. For protection of the piston from damages it is necessary to lay wooden whetstones. It is possible to use also old block
13. Press the piston into the cylinder (fig. 8.17). For this purpose use a wooden kiyanka or a special clamp. At the same time do not damage the surface of the piston or an antisplash cover.
14. At cave-in of the piston brake fluid from the cylinder will be forced out in a tank. If necessary pump out surplus of liquid.
15. Establish brake shoes.
16. Install the wear sensor.
17. Establish a support and tighten the new self-fixed directing fingers the moment of 35 N · m.
18. Put on protective covers the directing fingers.
19. Connect the sensor socket. Pay attention to laying of a wire and close a protective cover of the socket.
20. Establish the holding support bracket. After installation of a bracket in both openings fix it by pressing under a support arm. At the wrong installation the course of a pedal of a brake will increase.
21. Establish a forward wheel, lower the car and tighten bolts of fastening of wheels the moment of 110 N · m.
22. Replace brake shoes on the other side of the car.
23. On the motionless car several times press a brake pedal that blocks adopted the correct provision.
24. Check the level of brake fluid.