It is the Audi Brake Line and Hoses that are used as conduits so the pressurized hydraulic fluid can be transported to the four wheels in an efficient manner. The construction of the brake lines and hoses is metal tubing for the brake lines and reinforced polymer for the hoses on your Audi vehicle.
The brake lines and hoses mounted to the braking system on your Audi are of a small diameter. This limited space for the hydraulic fluid to travel makes it possible for the transfer of the hydraulic fluid without the pressure in it diminishing to any appreciative degree.
If a leak does occur in either the brake line or hose, the amount of fluid lost is not great, but even a small amount will reduce the braking capacity of your Audi and should be repaired. When a leak is present, fluid loss will occur each time the brake pedal is depressed. When the brake pedal is released, air will replace the lost fluid in your system. A driver will notice this air because the brake pedal will feel soft and the pedal will have to travel farther to achieve the same stopping power as it had before the leak.
To locate the leak in either the brake line or hose, pressure has to be in the system. This is accomplished by the brake pedal being depressed. With an assistant helping the inspector, the leak can be found by locating the stream of brake fluid emanating from the Audit brake line or hose.
With the new brake line or hose installed on your vehicle and the trapped air removed, the braking system on your vehicle will function as it did before the leak occurred.