Audi A4, S4

Since 2000 of release

Repair and car operation

Audi A4, S4
+ Introduction
+ Controls and receptions of safe operation
+ Current leaving and service
+ The engine
+ Systems of cooling, heating and the air conditioner
+ Power supply systems, release and decrease in toxicity of the fulfilled gases
+ Systems of an electric equipment of the engine
+ Manual box of a gear change
+ Automatic transmission
+ Coupling, power shafts and differential
- Brake system
   Removal of air from brake system
   Removal and installation of lobbies brake колодок
   Removal and installation колодок brake mechanisms of back wheels
   Check of a thickness of a brake disk
   Removal and installation of a brake disk/support
   Adjustment of a lay brake
   Removal and installation of the switch of a stoplight
   Removal and installation of a brake hose
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment

Brake system

The basic data

The brake system consists of the main brake cylinder, the amplifier of a brake and disk brake mechanisms of forward and back wheels. The hydraulic brake system has two contours, operating диагонально. One contour influences on forward right/back left тормозы, the second contour operates on forward left/back right тормозы. At refusal of one of contours, for example, owing to leak of a liquid car braking is carried out by other contour. Pressure of a liquid in both contours is created by the dual main brake cylinder operating from a pedal of a brake.

The tank with a brake liquid is in an impellent compartment, over the main brake cylinder. It supplies with a brake liquid all system.

The amplifier of a brake at the petrol engine accumulates a part of the vacuum created in the soaked up pipeline of the engine. By pressing of a pedal of a brake the effort to it decreases owing to strengthening action of vacuum. As the diesel engine does not have necessary vacuum on всасывании, models with the diesel engine have the special vacuum pump. The vacuum pump is established ahead on a head of cylinders and set in motion from a camshaft.

The car has as ahead, so behind disk brakes with floating скобой a support. At such design one piston provides pressing of both brake колодок to a brake disk.

At movement on wet roads it is necessary to press periodically a pedal of a brake for drying of disk brakes. Owing to the centrifugal force arising in the course of movement of the car, water is dumped from disks. However there is a thin film of products of deterioration of rubber, greasing and the pollution interfering effective operation of brakes.

The dirt and water on a surface brake колодок lead to formation of furrows on a surface of brake disks that reduces efficiency of braking.

At cleaning of brake system the dust which can harm to health of the person is allocated, therefore to inhale a brake dust it is impossible.

ABS/The amplifier of emergency braking/EBV/EDS

Works with elektronno-operated elements of brake system and movement system are authorised to be made only to the experts having corresponding preparation.

ABS: the Antiblocking system interferes with blocking of wheels at sharp braking of the car. It promotes preservation of controllability by the car in the course of braking and raises traffic safety.

The amplifier of emergency braking: the Electronic system of the amplifier on the basis of speed of moving of a pedal of a brake and pressure upon a pedal distinguishes an emergency. In such situation the amplifier automatically during milliseconds raises the brake pressure set by the driver, to border of blocking of wheels.

EBV: the System of electronic distribution of brake effort by means of ABS-hydraulics distributes brake effort between forward and back wheels. As electronic system EBV works essentially more sensitively, than a regulator of brake effort operating mechanically it is used essentially больший a regulation range.

At movement on a straight line back brakes participate at the full capacity in the course of braking. To provide stability of the car as well at braking on turns, it is necessary to reduce participation in process of braking of back brakes. Through gauges of number of turns ABS system EBV receives the information, whether the car directly moves or does turn. At realisation of turn braking by back brake mechanisms decreases. Thanks to it back wheels can keep the maximum lateral coupling with road.

EDS: the Elektronno-blocked differential, at трогании from a place brakes turned wheels. Thanks to it the twisting moment is redistributed on "pulling" wheels.

The electronic blocking differential operates at трогании from a place and is switched off automatically at achievement of speed of 40 km/hour. Advantages of this system are absence of negative influence on road performance and preservation of comfort of management at трогании the car from a place.

Instructions on systems ABS/EBV/EDV

The safety scheme in the electronic block of management watches that the system in the presence of any defect (for example, cable breakage) or at too low working pressure (pressure of the storage battery more low 10) was disconnected itself. It is displayed on the panel of devices by fire of control lamps. The usual system of braking remains thus efficient. The car at braking behaves as if ABS is absent.

If during movement control lamps ABS and brake system at strong braking back wheels since distribution of brake effort has failed are blocked burn.

If during movement control lamp ABS lights up:


  1. Stop the car, switch off the engine and again start it.
  2. Check up pressure of the storage battery. If pressure more low 10.5 In, charge the battery.

If control lamps light up in a start of motion and after a while die away, it specifies that at first pressure of the battery at first was too low. Then it raises owing to gymnastics of the battery from the generator.

  1. Check up, whether plugs of the battery are reliably fixed and whether there is a reliable contact.
  2. Lift and establish the car on supports, remove wheels and check up electric wires of gauges of number of turns on presence of external damages (a place of retyrannies). More careful check of systems ABS/EBV/EDV should be spent in conditions HUNDRED.

Before carrying out of electrowelding works it is necessary расстыковать a socket of the block of management of hydraulics in an impellent compartment. The socket undocks at the switched off ignition. At colouring the management block can quickly be exposed to temperature not above +95С and during longer time (no more than 2 hour) to temperature not above +85С.