All brake mechanisms are equipped with self-adjusters. At the same time, the wear compensation of the brake pads of the disc mechanisms is carried out automatically, while special adjustment devices are installed on the drum mechanisms, the activation of which occurs when the parking brake is cocked.
Master brake cylinder (GTZ) mounted on the brake booster servo assembly mounted on the rear bulkhead of the engine compartment. On top of the cylinder is a large hydraulic fluid reservoir equipped with a plastic cap.
GTZ has a dual design, providing the operation of two independent hydraulic circuits (front and back). The fluid pressure in each of the circuits is pumped by an individual piston inside the separate chambers of the master cylinder. Since the GTZ primary piston is directly (through a metal rod) connected to the foot brake pedal, the movement of the latter inevitably leads to an increase in hydraulic pressure inside the brake lines. An instantaneous increase in pressure in the lines leads to the movement of the pistons in the calipers / wheel cylinders of the brake mechanisms, and the magnitude of the force developed by the latter increases in proportion to the increment in the area of their pistons relative to the area of the GTZ pistons.
The wheel cylinders of the drum brake mechanisms are equipped with two pistons that are pushed out in opposite directions and ensure that the brake shoes are pressed against the working surface of the drum. In disc mechanisms, the cylinders are built into the caliper assemblies and provide the ability to compress the brake disc between two friction pads.
Brake pads/shoes, as well as GTZ pistons, are equipped with return springs, which guarantees the transition of the system to its original state when the foot brake pedal is released.
The tightness of the pistons in the cylinders is ensured by the use of rubber sealing cuffs; special anthers are provided to protect the cylinders from dirt and moisture.
Master brake cylinder
Dual-circuit brake master cylinders use two pistons mounted directly one behind the other. The primary piston is directly connected to the brake pedal by means of a metal rod. The secondary piston is driven hydraulically by means of a fluid volume contained between the pistons. When leaks form in front of the secondary piston, the latter is shifted forward until it stops against the end wall of the cylinder and the liquid between the pistons enters only the rear brake circuit of the system. In the event of leakage in the rear circuit, the primary piston rests directly against the end of the secondary, providing isolation of the defective section of the tract.
Hydraulic path
All dual braking systems have the ability to warn the driver if one of the hydraulic circuits fails. The sensor-switch is usually built into the valve body, mounted on the rear bulkhead of the engine compartment, or on the frame under the GTZ assembly. The valve contains a piston that is simultaneously connected to both circuits of the hydraulic path in such a way that the pressure developed in them is applied to the corresponding side of the piston. With serviceable circuits, the pressures in both circuits are equal and the piston remains motionless. Any imbalance leads to displacement of the piston and closing of the sensor-switch, the circuit of which includes a special control lamp installed on the dashboard of the car. In addition to the sensor-switch, the valve assembly may also include a metering valve that provides a delay in the supply of pressure to the front circuit until the drum brakes of the rear wheels start to operate, which makes it possible to avoid braking the car with only the front wheels.
A special valve regulator allows you to control the pressure in the wheel cylinders of the rear brake mechanisms, thereby preventing premature blocking of the rear wheels during heavy braking.
Check of serviceability of functioning of a control lamp can be carried out by squeezing out of a pedal of a foot brake at the open valve of prorolling of one of brake mechanisms. If necessary, replace the lamp, or check the proper wiring and carry out the necessary repairs.
Vacuum booster
A special vacuum booster, which is standard on all models, uses the vacuum created in the intake piping to improve the efficiency of the hydraulic brake system. The vacuum booster servo is mounted on the rear bulkhead of the engine compartment inside the latter.
Anti-lock brake system (ABS)
ABS prevents premature blocking of the car's wheels during heavy braking (see Section Replacement of the gauge switch of stoplights).
Parking brake
The cable drive of the parking brake is connected to the brake mechanisms of the rear wheels of the car. Drive cables are connected to the actuating levers of the brake shoe assemblies.
Service
Upon completion of any of the maintenance procedures associated with the removal or disassembly of any of the components of the brake system, it is imperative to check the effectiveness of the brake system, and only after making sure that it is in full working order, start operating the vehicle. Road trials should be carried out on a clean, dry and level road surface.
Test the braking performance of the vehicle at different speeds and different pedal pressures. The car must brake evenly, while maintaining directional stability. Try to prevent premature wheel lockup, which could lead to loss of control.
Keep in mind that factors that affect a vehicle's braking performance include the condition and inflation pressure of the tires, the vehicle's load level, and the correct suspension geometry.
Precautionary measures
Some special precautions should be observed when servicing vehicle brake system components:
- a) Use only DOT 3 grade hydraulic fluid to fill the brake system;
- b) Friction linings of brake pads/shoes may contain hazardous asbestos. Try not to inhale brake dust, do not blow it off with compressed air. To wipe the components of the brake mechanisms, use only special cleaning compounds;
- c) Ensure that all required tolerances and tightening torques of fasteners are observed. When servicing components, use only serviceable tools. At the slightest doubt, seek help from specialists. Remember that the proper functioning of the brakes is the key to traffic safety;
- d) At the slightest sign of a malfunction in the functioning of the brake system, the operation of the car should be suspended!