Fig. 12.34. Drum brake mechanism of a back wheel: 1 – bolt of fastening of the working brake cylinder; 2 – cap of a viewing opening; 3 – lever axis; 4 – brake board; 5 – knot of the working brake cylinder; 6 – brake shoe; 7 – knot of the adjusting device of a brake; 8 – top returnable spring; 9 – clamping spring; 10 – washer; 11 – brake drum; 12 – adjusting screw; 13 – lower returnable spring; 14 – connecting link; 15 – spring of the adjusting device; 16 – brake shoe; 17 – lever of the adjusting device

The brake mechanism of back wheels of drum type from the leader and conducted by brake shoes (fig. 12.34). At such design of brakes the top coupling spring presses both brake shoes to the working brake cylinder, and the lower coupling spring presses them to a motionless emphasis. When pressing a brake pedal the piston of the brake cylinder of a wheel presses both brake shoes to the internal surface of the brake drum. Friction force creates torque which at the movement of the car presses the leading brake shoe to the brake drum even stronger forward. At the movement of the car back the similar effect happens to the conducted brake shoe. The effort from brake shoes is transferred to a motionless emphasis, and through it – to a basic plate and a flange of a back axis.

At such design of a brake there is an automatic adjustment of a gap after a brake pedal otpuskaniye. Besides, at such design brake overlays of the leading brake shoe usually wear out quicker, than at the conducted block. If brakes were operated, then to interchange the position of blocks inadmissibly as at the same time the effect of automatic increase in brake effort can be broken that will lead to the increased brake pedal course.

       PREVENTION

At repair of the working brake cylinder it is necessary to replace all details included in repair set.

Do not blow a detail of the brake system the air from the compressor containing vapors of oils. It can lead to damage of rubber details of knots.

When dismantling knots of the hydraulic drive of the brake system there can be a need of pumping of all brake system or its part.

Values of the moments of an inhaling of fasteners are given for the dry, not greased carving surfaces.

Operations on service of details of the cylinder have to be performed on a pure dry workbench without danger of pollution of details by mineral oils.

       PREVENTION

At service of details of the brake mechanism do not kick up dust when processing by a grinding wheel, cleaning of overlays of brake shoes or when cleaning details of brakes with a dry brush or compressed air of the compressor. For this purpose it is necessary to use a damp rag. Overlays of brake shoes contain asbestos fibers from which dust can get to air at service of brakes. Inhalation of the dust containing asbestos can cause serious damage to health.

1. Lift the car on the elevator.

2. Note provisions of rims in relation to naves and remove back wheels.

3. Turn off nuts of fastening of the thermal screen and put the thermal screen from above on the muffler.

4. Weaken a tension of the parking brake.

5. Turn out the adjusting screw of fastening of the brake drum.

6. Remove the brake drum.

If at removal of a drum there are difficulties, perform the following operations:

– be convinced that the parking brake is released;

– weaken a tension of the parking brake;

– get a cap from a viewing opening in a brake board and, using the screw-driver, wring out the lever of the drive of the parking brake so that the limiter of the course of the lever of the parking brake leaned on a brake shoe.

7. Remove top and lower returnable springs.

8. Remove the lever and a spring of the mechanism of adjustment.

9. Remove adjustment mechanism knot.

10. Remove brake shoes from a basic plate.

Fig. 12.35. Knot of the adjusting mechanism: 1 – adjustment mechanism screw; 2 – nut; 3 – spring bracket; 4 – adjustment mechanism plug

Clear knot of the adjusting mechanism (fig. 12.35).

Fig. 12.36. Points of putting lubricant on a brake board

Apply brake lubricant on a brake board in the places shown in the drawing 12.36.

Check that the threaded connection of the adjusting device rotates freely.

Replace all details, quality or durability of which cause suspicion because of change of the color caused by an overheat, excess loading or wear.

       PREVENTION

Before installation of the brake drum be convinced that the lock-nut 2 (see fig. 12.35) the adjusting device is tightened. On the end of an adjusting core the nut should not be tightened too strongly.

1. Grease a brake board in those places where it adjoins to brake shoes.

Fig. 12.37. Elements of the back brake mechanism: 1 – top returnable spring; 2 – lever of the drive of the parking brake; 3 – brake shoe; 4 – lever of the adjusting mechanism; 5 – brake shoe; 6 – adjustment mechanism screw; 7 – adjustment mechanism nut; 8 – spring of the adjusting mechanism; 9 – spring bracket

2. Connect the lever of the drive of the parking brake 2 (fig. 12.37) to a cable of the parking brake.

3. Establish a brake shoe with a slip to a basic plate by means of a clamping spring, a washer and a finger. Make sure that the cable of the parking brake is laid correctly.

4. Install the adjusting mechanism, brake shoes with slips and the lower returnable spring on a basic plate. Tighten nuts of fastening of a plate.

       PREVENTION

Do not stretch the lower returnable spring of the lever of the drive too strongly

The lower returnable spring has to settle down below a support corner.

5. Establish a clamping spring, a washer and a finger.

6. Install the adjustment mechanism. Turning, drown the basic lever of the mechanism in the coupling.

Install the adjusting mechanism into place which it occupied before dismantling (see fig. 12.37). Establish a spring bracket by a section to a basic plate.

7. Install the lever of the adjusting mechanism on a finger and connect to it a spring.

       PREVENTION

Fig. 12.38. Working brake cylinder: 1 – protective cap of the piston; 2 – piston; 4 – pumping union; 5 – case of the working brake cylinder; 6 – piston sealant; 7 – a spring 3 – a protective cap of the union

Do not stretch a spring 7 (see fig. 12.38) the drive lever too strongly

8. Establish a connecting link 14 (see fig. 12.34) on a finger and in a block opening

9. Establish the top returnable spring 8 to a connecting link 14 and to a block.

       PREVENTION

Do not stretch the top returnable spring too strongly

10. Install the brake drum 11 and fix it by the adjusting screw 12.

11. Establish back wheels and fix them by bolts.

Adjust brakes of back wheels.

Adjust the parking brake.

Press and release a pedal of a brake of at least 15 times until on both drums clicks of the spring of the adjusting mechanism touching an adjusting nut are not heard.

1. Raise and fix the car at convenient height.

2. Note the provision of rims in relation to naves and remove back wheels.

3. Turn out the adjusting screw of fastening of the brake drum.

4. Remove the brake drum.

Turn knot of the adjusting mechanism before the full choice of a gap.

Make sure that the limiter of the course of the lever of the parking brake is located opposite to an edge of a brake shoe. If it not so, release a few compensator of a cable of the parking brake.

1. Install brake drums and wheels.

2. Lower the car

3. Press and release a brake pedal several times until stop being clicks of the lever of the adjusting mechanism are heard.

It is necessary to press a pedal of a brake more than 10 times.

After clicks stop being are heard, the gap between brake shoes and the brake drum will be adjusted.

4. Adjust the parking brake.

1. Adjust back brakes.

2. Lower the lever of the parking brake.

3. Lift the car and fix at necessary height.

4. Check that the cable of the parking brake freely moves.

5. Turn off bolts of fastening of the heat-shielding screen and shift it aside.

6. Turn самоконтрящуюся a nut on a tip of the tension device of the parking brake until back wheels become difficult to be turned.

7. Turn off самоконтрящуюся a nut until when back wheels are able freely to turn.

8. After adjustment check the provision of a cam of the lever of the parking brake. It has to lie or be raised no more than on 0,2 mm.

9. Install into place the heat-shielding screen and fix it by bolts. Adjustment of the parking brake can be checked also by position of the limiter of the course of the lever of the drive of the parking brake. For this purpose perform the following operations:

– remove a cap from a viewing opening of a brake board;

– the limiter of the course of the parking brake has to settle down at distance of 3 mm from an edge of a brake shoe;

– insert a cap into a viewing opening of a brake board;

– lower the car.

1. Lift the car and fix at convenient height.

2. Remove details of the brake mechanism.

3. Remove nave knot.

4. Remove the holder of a cable of the parking brake.

5. Disconnect the brake pipeline from the working brake cylinder. For prevention of an effluence and pollution of brake fluid close an opening in the pipeline.

6. Remove the working brake cylinder from a brake board and a brake board.

       PREVENTION

Before installation of brake shoes apply a thin film of plastic PLASTILUB lubricant on contact surfaces of blocks.

Turn off an adjusting nut 7 (see fig. 12.37) against the stop. Collect knot of the adjusting mechanism and insert between blocks, having checked correctness of installation. On the end of an adjusting core the nut cannot be tightened too strongly (see fig. 12.35).

1. Establish cardboard laying on a new brake board.

2. Install a brake board 4 (see fig. 12.34) on the lever of a back suspension bracket and fix by bolts, having tightened their moment 28 N • m.

3. Install the working brake cylinder on a brake board and fix by bolts, having tightened their moment 9 N • m.

4. Connect the brake pipeline to the working brake cylinder and tighten a connecting nut the moment of 11 N • m.

5. Establish a cable of the parking brake and the holder of a cable.

6. Establish knot of a nave of a back wheel.

7. Establish all earlier removed details.

8. Pump over brakes.

1. Lift the car and fix at convenient height.

2. Note the provision of rims in relation to naves and remove back wheels.

3. Turn out the adjusting screw of fastening of the brake drum.

4. Remove the brake drum.

5. Remove the top returnable spring.

Note the provision of adjustment of brakes 7 (see fig. 12.34) the lever of the mechanism 17 and a spring of the mechanism 15.

Press brake shoes a little that to move apart them.

Purify dirt and foreign materials around connection of the brake pipeline to the working brake cylinder and bolts.

6. Disconnect the brake pipeline from the working brake cylinder.

For prevention of an effluence and pollution of brake fluid open openings in the pipeline need to be closed suitable traffic jams.

7. Turn out bolts and remove the working brake cylinder 5 (fig. 12.38).

1. Install the working brake cylinder on a brake board and fix by bolts, having tightened their moment 9 N • m.

2. Connect the brake pipeline to the working brake cylinder and tighten a connecting nut the moment of 11 N • m.

3. Install brake shoes on the brake cylinder.

4. Establish the top returnable spring.

Position of the mechanism of adjustment 7 (see fig. 12.34) and the mechanism 17 lever with a spring has to be same, as well as before removal.

5. Install the brake drum 11 and fix it by the adjusting screw 12.

6. Establish back wheels and fix them by bolts.

7. Pump over the brake system.

Adjust brakes of back wheels.

Adjust the parking brake.

1. Remove the working brake cylinder 5 (see fig. 12.38) from a brake board.

2. Remove protective caps 1.

3. Remove pistons 2 and a sealant 6.

4. Remove a spring 7.

5. Remove a protective cap 3 and turn out the union of pumping 4.

Check a condition of an internal surface of the cylinder and the surface of the piston for existence:

– scratches;

– zadir;

– corrosion;

– wear.

For removal of traces of corrosion use polishing material.

If polishing did not possible to remove corrosion traces, replace the working brake cylinder.

Wash out all details pure brake fluid or denatured alcohol.

Dry up details the air from the compressor which is not containing oils.

Before assembly grease new a sealant, pistons and the internal surface of the case of the cylinder with pure brake fluid.

       PREVENTION

Before assembly of the working brake cylinder apply a thin film of paste for drum brakes on new rubber details (except antidust caps) and the internal surface of the working brake cylinder.

1. Screw the union 4 and establish a cap 3.

2. Establish a spring 7.

3. Install pistons 2 and a sealant 6.

4. Establish protective caps 1. Check pistons 2 regarding free movement.

5. Install the working brake cylinder on a brake board.

Brake board of a drum brake......... 28 N • m

Bolt of fastening of the brake cylinder to a brake board........ 9 N • m

Brake pipeline........ 11 N • m