General information
Depending on the modification of the car, different brake mechanisms can be installed (see specs).
The brake system is divided diagonally into two independent hydraulic circuits and consists of a master brake cylinder (GTZ) with a vacuum booster, vacuum hose, brake hydraulic lines and brake mechanisms. If one of the circuits fails (for example, as a result of seal failure) the second continues to function normally, providing adequate braking of the vehicle. Fluid pressure in both circuits is created by a tandem brake master cylinder (GTZ). The GTZ is activated when the brake pedal is depressed. The brake fluid reservoir is attached to the GTZ.
The brake booster stores part of the vacuum created in the engine intake manifold. On diesel and gasoline engines of 1.8, 2.0 and 3.6 liters, additional vacuum for reliable operation of the vacuum booster is created by a vacuum pump.
The parking brake is a traditional, cable-operated lever acting on the rear brakes.
The procedures for bleeding and checking the brake system, as well as changing the brake fluid are described in Sections 8-9 of Chapter 1.
When checking the brake system, the wheels are driven by a single-axis roller dynamometer at a maximum speed of 6 km/h. During the test, the transmission must be in neutral. When the ignition is off, the auxiliary functions of the brake system do not work. On AWD models, a single axle roller dynamometer must be used, on which the rollers for different wheels rotate in different directions - this prevents the transfer of braking forces to the transmission line. In this case, the measurement is made only for the wheel rotating forward, i.e. verification is required twice. If the specified dynamometer is not available, follow the following procedure to check on a conventional single-axis roller dynamometer. Put the front wheels on casters, turn off the engine, wait about two seconds and check the front brakes. Start the engine, wait about 5 seconds (until there is sufficient vacuum) and put the rear wheels on rollers. Stop the engine, wait about two seconds and check the rear brakes. Start the engine and wait approximately 5 seconds (until there is sufficient vacuum).
The ABS or ESP system with various additional functions is installed as standard. A description of the ABS/ESP and their functions is provided in Section 24 Chapter "Controls and methods of operation".
To control the operation of the brake system and the ABS / ESP system, the corresponding indicator lamps are used in the instrument cluster (see Chapter 13 "Controls and methods of operation").
Security measures
Brake fluid is one of the highly toxic and chemically aggressive compounds and, in contact with body panels, destroys the paintwork.
The dust produced during the wear of the brake pads may contain asbestos, which is harmful to human health - in no case inhale it when cleaning the brake mechanisms!
Working with the brake system requires special cleanliness and strict adherence to instructions. In the absence of the necessary experience, it is advisable to contact the service station.
Note: When driving on wet roads, periodically depress the brake pedal to remove moisture from the brake discs. In the process of wheel rotation, moisture is discharged from the brake discs under the action of centrifugal force, but a silicone film, rubber abrasion products, grease and other contaminants that reduce braking efficiency remain!
Corrosion-damaged disc brakes create a shaking effect during braking that does not disappear with time. In this case, the disks should be replaced.
Dirt sticking to the surface of the brake pads leads to the formation of grooves on the surface of the brake discs, which leads to a decrease in braking efficiency.
When checking on a roller dynamometer, the transmission must be in neutral. The maximum control speed must not exceed 6 km/h.
Notes on repair work on the ABS/ESP system
When performing any repair work on the ABS / ESP, first of all, determine the cause of the malfunction using a diagnostic tool connected to the vehicle's diagnostic connector (see chapter 5).
Observe general safety precautions when handling brake fluid. After performing work in which the hydraulic circuit of the brakes was opened, air must be removed from the hydraulic actuator (pump it up, see chapter 1). Maintain impeccable cleanliness, never use accessories containing mineral oils.
Thoroughly clean the connections and the area around them before disconnecting the brake lines. When doing this, do not use aggressive detergents, gasoline, solvents, etc.
Lay the removed parts on a clean surface and cover them.
After separating the control unit from the hydraulic modulator, use the transport protection for the connector contacts.
If repairs cannot be made immediately, cover or plug exposed components.
Use only lint-free cloth.
Unpack spare parts only immediately before installing them. With the system open, do not work with compressed air or move the vehicle.
When painting the vehicle, the ABS/ESP electronic control unit may only be subjected to a maximum temperature of 95°C for a short period. Exposure to 85°C is allowed for approximately 2 hours.