Some VW Passat cars in addition to ABS system can be equipped with system of the electronic mechanism of blocking of differential (EDS). Being additional in relation to ABS system, the EDS system reduces transfer of a torque of the engine under adverse traffic conditions, especially, on liftings and at car accelerations by a method of elimination of pro-slipping of one of driving wheels, and also a troganiya from a place and dispersal. Thanks to the electronic mechanism of blocking of differential improvement of transfer of a torque as thus the party with great value of factor of a friction can transfer a bigger torque is reached. Electronic blocking of differential starts to operate at a troganiye from a place and is automatically disconnected for speed of 40 km/h. That in a troganiye mode from a place it does not render negative influence on a mode of movement of the car and comfort of management belongs to one of advantages of such way of improvement of traction effort.

Principle of action of EDS

Fig. 12.22. Brake system of the car equipped with ABS: 1–ABS sensor; 2–forward brake disk; 3–ABS sensor rotor; 4–electronic ABS control unit; 5–back brake disk; 6–electric conducting; 7–hydraulic modulator; 8–block of valves; 9–brake tubes

The electronic control unit receives constant information from ABS sensors about speed of rotation of driving wheels and in the presence of a difference of number of turns over about 110 mines-1 of EDS joins automatically and reduces torque transfer by a revolving wheel until its speed will be approximately equal speed of slipping wheels. Thanks to such management with the best conditions of coupling with the road the increased torque is transferred to a wheel. The EDS system as it was already mentioned, is automatically disconnected at speed of movement of the car over 40 km/h, and also during the passing of turns and an overheat of brakes. The EDS system is reliably protected from failures of management by brakes. In EDS system are used a number of elements of ABS system. In case the car is equipped with EDS system, the hydraulic ABS unit is equipped with the additional block of EDS valves, and the electronic ABS 4 control unit (fig. 12.22) has "vshity" program memory of EDS.

Hydraulic block

Fig. 12.23. ABS block: 1–pusher; 2–pressure accumulator; 3–hydraulic pump; 4–block of valves; 5–main brake cylinder; 6–tank; 7–stopper

The hydraulic block and its components are presented on fig. 12.23 and 12.24 .

Fig. 12.24. ABS block elements: 1–stopper; 2–tank; 3–clip of brake tubes; 4–arm; 5–nut; 6–bolt; 7–laying; 8–pressure sensor; 9–connecting hose; 10-pressure accumulator; 11-sealing ring; 12-hydraulic pump; 13-brake tube; 14-block of valves; 15-block of the hydraulic amplifier and main brake cylinder; 16-sealing plug; 17-plug; 18-sealing ring

NOTE After carrying out any kind of repair work in anti-blocking system it is necessary to carry out diagnostics of serviceability of system at VW service station with use of the special equipment.

Removal of the hydraulic block make in the following order:

before the beginning of work disconnect a "minus" wire from the plug of the storage battery;

— to get access to the ABS control unit, cнимите an air inlet branch pipe between the air filter and the case of throttles;

— press a brake pedal about twenty times (thus made a brake pedal the effort should increase) to remove pressure in the pressure accumulator;

— disconnect electric sockets and the grounding tire from the ABS block;

— uncover a tank and pump out from a tank brake liquid;

— having unscrewed connecting nuts, disconnect brake tubes from the block. Muffle the ends of tubes the corresponding jams;

— in car salon from the driver remove the bottom furnish of the dashboard;

— remove a lock ring and take a pin from a pusher of a pedal of a brake;

— unscrew nuts of fastening of the hydraulic block and remove the block.

Installation make in sequence, return to removal.

Before installation of an air branch pipe remove air from brake system.

Electronic control unit

The electronic control unit is located under the left pillow of back sitting.

Removal of the block make in the following order:

— before the beginning of work disconnect a "minus" wire from the plug of the storage battery;

— remove a pillow of a back seat;

— release a clip and disconnect the contact electric socket from the block;

Fig. 12.25. Arrangement of screws of fastening of the electronic block управленияРис. 12.22. Brake system of the car equipped with ABS: 1–ABS sensor; 2–forward brake disk; 3–ABS sensor rotor; 4–electronic ABS control unit; 5–back brake disk; 6–electric conducting; 7–hydraulic modulator; 8–block of valves; 9–brake tubes

— having unscrewed two screws of fastening (fig. 12.25) , remove the electronic control unit.

Installation carry out to sequences, return to removal.

Be convinced that the clip accurately fixed the contact electric socket on the block.

Relay and safety locks

The anti-blocking system has two relays: one general relay of system and relay of the hydraulic pump. Both relays are placed over the main block of safety locks and the relay under the dashboard, from the driver.

Sensors of speed of a wheel

Fig. 12.26. Principle operation of the sensor of speed of a wheel: 1–sensor of speed of a wheel; 2–magnetic field; 3–gear rotor; 4–electric signal

The gear rotor 2 (fig. 12.26) of the sensor which has been rigidly fixed in a nave of a wheel, rotates together with a wheel. Teeths of the rotor passing through a magnetic field And the sensor 1, induce an electric signal In, proportional to speed of rotation of a wheel which is transferred to the electronic control unit.

Removal make in the following order:

— before the beginning of work disconnect a "minus" wire from the plug of the storage battery;

— will hang out a lobby or a back part of the car and fix on basic racks;

— remove the corresponding wheel;

Fig. 12.27. Sensor of speed of a wheel

— having unscrewed a fastening bolt, remove the sensor (fig. 12.27) from a rotary fist or a pin.

Installation of the sensor carry out to sequences, return to removal.

Before sensor installation, put on it paste for the brake cylinder.

Gear rotors of sensors

Forward gear rotors are located on internal surfaces of naves of a forward wheel.

For removal of a forward rotor remove a nave of a wheel and separate a rotor from a nave.

Back rotors are located in back naves of a brake disk.

Removal of a back rotor make in the following order:

— before the beginning of work disconnect a "minus" wire from the plug of the storage battery;

— for removal of a rotor remove a brake disk;

— pass a core through an opening under a bolt of fastening of a wheel and take a rotor from a nave.

Installation of rotors make in sequence, return to removal.

At installation of a gear rotor it is necessary use a tubular opravka of the corresponding diameter.

Pressure sensor

On early models of cars the sensor of pressure is established in the case of the main brake cylinder, and on the cars which are let out since January 1989, the sensor is established on the case of the hydraulic pump.