Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
+ System of injection
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
- Brake system
   Check of brake mechanisms
   Brake fluid
   Check of level of brake fluid
   Check of tightness of brake system
   Replacement of brake fluid
   Disk brake mechanisms
   Measurement of thickness of blocks of the disk mechanism
   Control of a condition of brake disks
   Replacement of blocks of disk brake mechanisms
   Drum brake mechanism
   Measurement of brake shoes of the drum mechanism
   Check of the course of a pedal of a brake
   Disk brake mechanism of back wheels
   Measurement of thickness of blocks of back disk brakes
   Check of a free wheeling of the lever of the parking brake
   Main brake cylinder
   Amplifier of brakes
   Check of the amplifier of brakes
   Regulator of brake forces
   Repair of the hydraulic drive of brakes
   Pumping of brake system
   List of malfunctions
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
+ System of ignition
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

Brake fluid

This yellowish – and, by the way, poisonous and aggressive in relation to an autovarnish – liquid does not corrode rubber and metal parts. It remains even at minus 40 °C still rather fluid, and its boiling point is located, despite the mentioned fluidity, on 260 °C.

But brake fluid possesses also one very unpleasant property: it easily absorbs water, it "is hygroscopic". Water can really get to brake fluid, for example through humidity of air: through a compensation tank, and also microscopic not tight places on hoses of brake system and rubber cuffs. Full absorption of water, however, does not lead to corrosion of metal parts of system, but to strong decrease in a boiling point. At only 2,5% of the content of water the boiling point is already only on 150 °C.

It is dangerous at high load of brakes because in this case they strongly heat up. Near the warmed brakes in working liquid vials of air can be formed. As air is squeezed – the brake pedal will fail in a floor! In this case only fast "podkachivaniye" a brake pedal can help. Especially dangerously this effect is shown when braking the car after strong load of brakes. Due to the lack of an obduv a counter flow elements of brakes heat up even more strongly; the greatest temperature is reached approximately after 15 min. the parking. Only half an hour later temperature of brake fluid again falls to the normal. Therefore the plan of servicing preventively orders replacement of brake fluid each two years.

Brake fluid has to conform to the FMVSS116DOT4 standard. All liquids marked thus without fears can be mixed one with another.