Audi A4

since 1994 of release

Repair and car operation



A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ exhaust System
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and absorption channels
+ injection System
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
- Brakes
   Independent work on brake system
   So the brake system works
   Check of brakes
   Brake liquid
   Check of level of brake liquid
   Check of brake system on tightness and existence of damages
   Replacement of brake liquid
   Disk brakes
   Measurement of thickness of overlays of forward disk brakes
   Check of a condition of brake disks
   Replacement of overlays of disk brakes
   Back disk brakes
   Measurement of overlays of back disk brakes
   Hand brake
   Check of idling of the lever of the hand brake
   Main brake cylinder
   Brake amplifier
   Check of the brake amplifier
   Works on hydraulics of brake system
   Pumping of brake system
   The help at malfunctions
   ABS and EDS
   What does ABS?
   Function of separate knots
   Electronic system of distribution of brake effort (EBV)
   Violations in ABS system work
   Electronic blocking of differential (EDS)
+ Wheels and tires
+ Electrotechnical equipment
+ ignition System
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics





Brake liquid

Between an impellent compartment and a windscreen in a so-called vlagoulavlivayushchy box the main brake cylinder (2) and the brake amplifier (3) take place a tank with brake liquid (1). In the photo marks of level of filling of a tank "MOVE" and «MIN» are well visible.

This yellowish, poisonous and aggressive liquid in relation to an automobile varnish does not corrode metal and rubber details. She remains rather zhidkotekuchy at–40 °C and, despite the жидкотекучесть, about about 260 °C possess extremely high boiling point.

But brake liquid possesses very unpleasant property: it willingly absorbs water, it "is hygroscopic". Water, for example at the expense of humidity of atmospheric air, can really get into brake liquid: through a broad tank or through microscopic not tight sites in brake hoses or in rubber cuffs. Such absorption of water leads not only to corrosion of metal details of brake system, but also causes fast fall of a boiling point of brake liquid. At the content of water in only 2,5 % its boiling point is only at 150 °C. Near the warmed-up brakes steam vials in hydraulic liquid can be formed. They are compressed – the pedal of a brake can deeply fail, sometimes the foot presses simply in emptiness! In this case fast pumping of liquid by a brake pedal sometimes helps. This effect is especially dangerous at a car stop after strong load of brakes. Because of a lack of a head wind everything being in an environment of brakes, is warmed up even more strongly. And approximately only in half an hour the temperature of brake liquid goes down to the normal.

Therefore the plan of maintenance orders preventive replacement of brake liquid every two years. Brake liquid should correspond to the FMVSS 116 DOT 4 specification. With such designation it is possible without fear to mix all liquids.