Audi A4 with 2001- 2005 of release.
1. Operation and car maintenance service
2. The engine
3. Transmission
4. A running gear
5. The steering mechanism
6. Brake system
6.1. Preliminary checks
6.1.1. Brake disks
6.1.2. Check of brake system
6.1.3. Replacement of a brake liquid
6.1.4. Visual check of brake system on presence негерметичности and damages
6.1.5. Check of a thickness of brake overlays
6.1.6. Check at high and at low pressure
6.1.7. Check of residual pressure
6.1.8. Troubleshooting at unilateral deterioration brake pads
6.1.9. Check of the main brake cylinder
6.1.10. Prorolling of brake system
6.1.11. Process of removal of air for cars with electronic system of maintenance of course stability (ESP)
6.2. Repair of brake system
6.3. Repair of brakes of forward wheels
6.4. System ABS
6.5. Tables
7. An onboard electric equipment
8. A body
9. Electric equipment schemes


6.1.2. Check of brake system

General provisions

Fig. 6.1. The diagramme of change of density of a brake liquid

With increase in the maintenance of water the boiling temperature goes down, i.e. at strong heating of a brake liquid there can be a formation of bubbles of steam and brake refusal (fig. 6.1).

The brake liquid гигроскопична, i.e. it is capable to absorb water and a moisture from air

The brake liquid darkens eventually. Dark colour of a brake liquid does not testify to its quality. Colour change arises because of chemical reactions, and it can occur, especially at cars with ABS, already after short time (some weeks).

Rubber parts of brake system (a cuff, манжетные consolidations) are susceptible to influence of mineral oils, gasoline and cleaners.

Fig. 6.2. A difference between the normal and "moistened" cuff: A – a cuff – the original size; B – the cuff – at wetting by mineral oil inflates

Already their smallest quantity on манжетном consolidation or a cuff conducts to change of details, and can worsen brake functioning. Consequences of the polluted brake system affect only after some months, and then demand considerable expenses, from cars with ABS (fig. 6.2).
To store capacities with a brake liquid follows always well closed. Only thus possibility of hit of oil, a dirt or a cleaner, and also a moisture is excluded from air.
Packings with a brake liquid to store separately from oil (and also hydraulic oil) and liquids for cleaning completely to exclude mixing of two liquids or even erroneous refuelling of brake system.

6.1.1. Brake disks

6.1.3. Replacement of a brake liquid