9.1. Features of a design

The UAZ Hunter car is equipped with two independent brake systems: working and parking. The first system equipped with the hydraulic drive provides braking at the movement of the car, the second — slows down the car on the parking, its drive mechanical.
On the car use the double-circuit working brake system with disk mechanisms on forward wheels and drum on back wheels. One contour gives mechanisms of forward wheels, and another — mechanisms of back wheels. At refusal of one of contours of the working brake system the second contour providing a car stop though with smaller efficiency is used. Both contours are put in action from a brake pedal which fastens to an arm on a body. The vacuum amplifier, the main brake cylinder, brake mechanisms of forward and back wheels with working cylinders, pipelines enter the hydraulic drive, besides a brake pedal.
The parking brake system has the manual mechanical drive on transmission.
The vacuum amplifier installed between the mechanism of a pedal of a brake and the main brake cylinder when braking due to depression in an engine receiver through a rod and the piston of the first camera of the main cylinder creates the additional effort proportional to effort from a pedal.
In the hose connecting the vacuum amplifier to a receiver the backpressure valve is installed. It holds depression in the amplifier at his falling in an inlet pipe and interferes with hit of fuel-air mix in the vacuum amplifier.
The main brake cylinder of the hydraulic drive of brakes consists of two separate cameras connected to independent hydraulic contours. The first camera is connected with forward brake mechanisms, the second — with back.
The main cylinder is supplied with a tank which internal cavity is divided by a partition into two compartments. Each compartment feeds one of cameras of the main cylinder.

Fig. 9.1. Brake mechanism of a forward wheel: 1 – clamping spring; 2 – brake shoes; 3 – bracket; 4 – support; 5 – perepuskny valve; 6 – cap; 7 – brake hose; 8 – brake disk; 9 – holder of a spring

Brake mechanisms of forward wheels disk, with automatic adjustment of a gap between brake shoes 2 (fig. 9.1) and a disk 8, with a floating bracket 3. The mobile bracket is formed by a support 4 with the two-piston working cylinder. The directing bracket of 3 blocks is attached by bolts to a rotary fist of a forward suspension bracket. The mobile bracket is attached by bolts to the directing fingers which are established in openings of the directing blocks. The directing plugs are greased with jellied lubricant and protected by rubber covers. In a cavity of the wheel cylinder the piston with a sealing ring is installed. Due to elasticity of this ring the optimum gap between blocks and the ventilated disk which surface is protected by a brake board is supported. When braking the piston under the influence of pressure of liquid presses an internal block to a disk, as a result of reaction force the support moves on fingers and the external block nestles on a disk too, and force of pressing of blocks is identical. At a disinhibition the piston due to elasticity of a sealing ring is taken away from a block, between blocks and a disk the small gap is formed.

Fig. 9.2. The brake mechanism of a back wheel of the car equipped with anti-blocking system of brakes: 1 – top coupling spring of blocks; 2 – basic racks of blocks; 3, 5 – brake shoes; 4, 6 – the directing fingers of blocks; 7 – brake cylinder

Brake mechanisms of back wheels drum, with automatic adjustment of a gap between blocks and a drum. Brake shoes 3 and 5 (fig. 9.2) are put in action by one hydraulic working cylinder 7 with two pistons.
The parking brake put in action mechanically consists of the lever, drafts with adjusting nuts, a cable and the drum brake located in front of the back driveshaft. The back tip of a cable is connected to the lever of the mechanism of the parking brake. The lever of the drive of the parking brake fixed between front seats on a floor tunnel is equipped with the mechanism of adjustment of a tension of cables.
The parking brake does not need special leaving. At maintenance check degree of wear of its details, be convinced of serviceability of teeths of the sector and a doggie. Replace excessively worn-out details.
At detection of break of covers or a provolok of a cable replace a cable new.

Good advice
Some drivers, seeking to wear out less a cable of the parking brake, try to use it less often. Such "economy" results in the return result: a cable, seldom moving in a cover, gradually loses mobility, gets jammed it, as a result the cable breaks. Therefore use the parking brake in all cases, when necessary.

Useful tips
The free wheeling of a pedal of a brake at the idle engine has to be about 8-11 mm. Too low free wheeling demonstrates jamming of the working cylinder, causes the increased fuel consumption and the accelerated wear of brake shoes. Too big free wheeling — a sign of excess gaps in the mechanism of a pedal or violation of tightness of a hydraulic actuator of the brake system. If the free wheeling decreases by numerous pressing a pedal, i.e. it becomes "more rigid", – in system air. If the full speed of a pedal begins to increase, the system is untight.
If when braking the pedal of a brake begins to vibrate, most likely, brake disks are jarred on. Unfortunately, in their such situation it is only necessary to change, and at once both.
If when braking begins to pull the car aside, check working cylinders: perhaps, their repair or replacement will be required.
If in a forward suspension bracket there was a knock vanishing when braking check an inhaling of bolts of fastening of a support.
After replacement of brake shoes prior to the movement surely several times press a brake pedal — pistons in working cylinders have to rise into place.