GENERAL INFORMATION

Specifications

CAUTION

Individual specifications are also given in the text of the chapter, and where their observance is mandatory they are printed in bold

Components of the electronic-hydraulic dynamic stability control system ABS/EBV/EDS 1 – ASR switch 2 – brake light switch 3 – rear left wheel speed sensor 4 – rear right wheel speed sensor 5 – front right wheel speed sensor 6 – front left wheel speed sensor 7 – ABS/EBV/EDS/ASR control unit, integrated in the hydraulic control unit 8 – ABS/EDS warning lamp 9 – ASR warning lamp 10 – brake fluid level warning lamp 11 – master brake cylinder, brake booster, brake pedal 12 – hydraulic control unit

ABS/EDS Control System Components 1 – brake master cylinder and brake booster 2 – hydraulic control unit 3 – diagnostic connector. In the center console under the ashtray. 4 – cover 5 – brake fluid reservoir warning lamp 6 – ABS/EDS warning lamp 7 – wheel speed sensor/sensor wheel. Rear axle 8 – brake light switch. Above the brake pedal 9 – wheel speed sensor/sensor wheel. Front axle

The brake system consists of a brake booster, a tandem brake master cylinder with an attached ABS hydraulic unit, and disc brakes on the front and rear wheels. The brake system has two diagonally split circuits. One circuit acts on the front right/rear left brakes, the other on the front left/rear right brakes. If one circuit fails, the vehicle is braked by one front and one rear brake. Hydraulic pressure in both circuits is generated in the tandem master cylinder by applying the brake pedal.

The brake fluid reservoir is located in the engine compartment above the brake master cylinder. It supplies fluid to the entire brake system.

The front wheels are fitted with ventilated disc brakes for better heat dissipation. The rear wheels are braked by solid disc brakes.

The brake booster uses part of the vacuum generated in the engine intake manifold. When the brake pedal is applied, the vacuum increases the pedal force through the brake booster.

The disc brakes use so-called fixed calipers. These calipers require only one piston to press the brake pads.

The parking brake acts on the rear wheel brakes through cables.

CAUTION

Work on the brake system requires special cleanliness and strict adherence to instructions. Without the necessary experience, it is advisable to contact a service station.

Brake pads are designed for use on a specific vehicle model. It is recommended to use brake pads approved by the manufacturer or the Federal Motor Transport Authority (KBA). Such brake pads are marked with the KBA mark.

CAUTION

When driving on wet roads, periodically press the brake pedal to dry the disc brakes. While the wheel rotates, water is thrown off the brake discs by centrifugal force, but a film of silicone, rubber abrasion products, grease and other contaminants remains, reducing braking effectiveness. Dirt buildup on the brake pads and rain grooves cause grooves on the brake disc surface, which reduces braking efficiency. Dust is produced when cleaning the brake system and may be harmful to health, so do not inhale brake dust.

ABS/EBV/EDS/ASR

ABS:

The anti-lock braking system prevents the wheels from locking during hard braking. This helps maintain steering control during braking and improves driving safety.

EBV:

Electronic Brake-force Distribution (EBD): using ABS hydraulics, distributes the braking force to the rear wheels. Since EBD control works considerably more sensitively than a mechanical brake force regulator, a much wider control range is used. When driving straight, braking force is fully transmitted to the rear wheels. To also ensure stability during braking in corners, the braking force on the rear wheels must be reduced. Using the ABS wheel speed sensors, the system determines whether the vehicle is driving straight or turning. When cornering, the rear wheel braking force is reduced. As a result, the rear wheels can generate maximum lateral guiding force. EDS: Electronic Differential Lock brakes spinning wheels when the vehicle starts moving, so that torque is transmitted to the driving wheels. The electronic differential lock operates when starting off and switches off automatically at a speed of 80 km/h. Key advantages of this system: it does not adversely affect driving dynamics or steering comfort. Notes on ABS/EBD/EDS systems: A special switch in the electronic control unit ensures that the system is switched off in case of a fault (for example, a broken cable) or if the on-board voltage drops below 10 V. This condition is indicated by the warning lamps lighting up on the instrument panel. The conventional brake system remains operational. During braking, the vehicle behaves as if the ABS system were not present.

CAUTION

If the ABS and brake system warning lamps come on while driving, the rear wheels may lock during hard braking because brake force distribution is not functioning. If one or more warning lamps come on in the instrument panel while driving, note the following:

PROCEDURE

1. Stop the vehicle briefly, switch off the engine, and restart it.

2. Check the battery voltage. If the voltage is below 10.5 V, charge the battery.

CAUTION

If the warning lamps come on at the start of driving and then go out after some time, this indicates that the battery voltage was initially too low and then increased again during driving as the generator charged the battery.

3. Check that the battery terminals are securely fastened and making good contact.

4. Raise the vehicle on stands, remove the wheels, and check the electrical wires running to the wheel speed sensors for external damage (chafing). A more detailed check of ABS/EBD/EDS must be carried out at a workshop.

CAUTION

Before performing electric welding, disconnect the control unit connector. The connection may only be disconnected with the ignition switched off. When performing paint work, the control unit may be briefly heated to no more than +95°C, or for a longer period (max. 2 hours) to no more than +85°C.