Brake Fluid; General Notes - Audi A6 2005 Workshop Manual

5

Brake fluid

5.1

General notes

Brake fluid is hygroscopic; in other words it has the tendency to
absorb water and moisture from the atmosphere.
The boiling point decreases as the water content increases, which
means that vapour bubbles can form when the brake fluid be‐
comes hot. This can cause brake failure.
The colour of the brake fluid becomes darker over the course of
time. A dark brake fluid colour is not an indication of its condition.
The change in colour is caused by chemical reactions and may
occur within a short period (several weeks), particularly in vehi‐
cles equipped with ABS.
WARNING
Rubber brake system components (rubber sleeves, seals) are
not compatible with mineral oil, petrol and cleaning agents.
Even minute quantities coming into contact with a seal or rubber
sleeve will affect the component and could impair brake opera‐
tion. The consequences of a contaminated brake system only
become apparent months later, and then give rise to greater ex‐
penses, particularly in vehicles equipped with ABS.
A = Rubber sleeve (original size)
B = Rubber sleeve (swollen due to contact with mineral oil)
Summary of the above mentioned points:
Always keep brake fluid containers properly sealed. This is the
only way of preventing contamination by oil, dirt, cleaning agents
or moisture.
Brake fluid containers should be kept completely separate from
oils (including hydraulic fluid) and cleaning agents to prevent any
mixture of fluids or even filling of the brake system with an incor‐
rect fluid.
We recommend using brake fluid approved by Audi ⇒ ETKA .⇒
Audi A6 2005 ➤ , Audi A6 Avant 2005 ➤
Brake system - Edition 04.2019
25
5. Brake fluid