10.3. Drum brakes

Replacement of brake shoes

Fig. 10.7. Back drum brake mechanism: 1 – tube of the brake system; 2 – the holding pins and springs; 3 – protection cover of a back brake; 4 – laying; 5 – adjusting lever; 6 – adjusting level; 7 – springs are protivoskripny; 8 – secondary brake shoe; 9 – bracket; 10 – brake drum; 11 – nave nut; 12 – returnable spring; 13 – primary brake shoe; 14 – working brake cylinder; 15 – bolt; 16 – bolt of fastening of the working brake cylinder; 17 – cable of the parking brake; 18 – rubber cap; 19 – union of removal of air; 20 – steel ball; 21 – dustproof cover; 22 – piston; 23 – piston cuffs; 24 – spring cup; 25 – spring


Elements of the back drum brake mechanism are shown in fig. 10.7.
Lift the car and reliably fix on supports.
Remove a wheel.

PREVENTIONS
Surely replace all blocks on one axis of the car even if only one is worn-out.
Do not mix a detail of the left and right brake mechanisms, work on each brake mechanism in turn.
If old brake shoes establish again, before removal they need to be marked.
During the work with the brake system you remember every time that at attrition of brake shoes the dust containing asbestos which is noxious to health is formed.

Fig. 10.8. Use of the screw-driver for release of the springs fixing brake shoes: 1 – the springs fixing brake shoes; 2 – control lever; 3 – protection cover of a back brake; 4 – screw-driver


Remove knot of a brake drum / nave. If the brake drum cannot be removed easily at once, remove a stopper in the protection cover of a back brake, through an opening insert the screw-driver and press the fixing spring for increase in a gap between brake shoes and the brake drum, as shown in fig. 10.8. If it does not allow to remove a drum, weaken an adjusting nut of the lever of the parking brake to increase the course of blocks.
Remove returnable springs of brake shoes.
Remove the fixing springs and pins.

Fig. 10.9. Use of the screw-driver and the direction of pressing for release of an adjusting level


Remove primary brake shoe and an adjusting level. Perhaps, it will be required to release an adjusting level by means of the screw-driver, as shown in fig. 10.9. It will facilitate removal of primary brake shoe.
Remove a secondary brake shoe and disconnect a cable of the parking brake.
Remove a bracket and disconnect a control lever from a brake shoe.

Fig. 10.10. Places of putting lubricant on the protection cover of a back brake


Grease the contact surfaces of the protection cover of a back brake with a thin layer of lubricant of white color on the basis of lithium in the points shown in fig. 10.10. Be careful not to allow hit of lubricant and other pollution on the surface of friction.
Establish a control lever on a new secondary brake shoe.
Establish a secondary brake shoe with a protivoskripny spring.
Connect a cable of the parking brake.
Collect primary brake shoe and an adjusting level, connect a level to a protivoskripny spring.
Establish the fixing spring.
Establish returnable springs.
Center assembly of brake shoes.
Examine the brake drum on existence of cracks, scratches, deep рисок and spots which will be shown as sites with the changed color. If spots cannot be removed with a fine-grained emery paper, it is necessary to deliver the brake drum in a workshop for regrinding. If the drum cannot be pereshlifovat without excess of the most admissible diameter of a drum, replace a drum new.
Establish nave knot / the brake drum and wheel bearings.
Establish a wheel, screw bolts and tighten them the required moment, lower the car.
Remove air from the hydraulic drive of the brake system.
Check operation of the parking brake and in case of need adjust it.
Several times press a brake pedal that brake shoes were established with a certain gap in relation to the brake drum, fill a tank with brake fluid.
Avoid sharp braking as far as it is possible, the first several hundreds of kilometers of a run of the car until new blocks get used completely.

Working brake cylinder
Removal
Lift a back part of the car and reliably fix on supports.
Remove knot of brake shoes.
Carefully purify all dirt from area around the working brake cylinder.
Turn off a cap nut, disconnect and close a suitable stopper a brake tube. Turn off two bolts of fastening of the working brake cylinder.
Remove the working brake cylinder from the protection cover of a back brake and put on a pure workbench.
Several times press a brake pedal that brake shoes were established with a certain gap in relation to the brake drum.