AudiWorld Forums

Audi A4 B7/B8: How to Replace Brake Line

A small leak in a small brake line could affect your whole brake system in the Audi A4 B7 or B8. Read on to learn how to replace the brake line.

By Bassem Girgis - March 23, 2016

This article applies to the Audi A4 B7 and A4 B8 (2004-2015).

The brake system in the Audi A4 B7 or B8 works off of hydraulic pressure. Any small leak in one of the brake lines will not only allow the fluid to leak, but also allows air to go inside the system. When the air goes in your pressurized brake system, the brake pedal starts feeling spongy, and your brake performance starts decreasing rapidly. Replacing a brake line is a bit more than just a quick swap, you will have to bleed your brake system after. Read on to learn how to replace your brake line and then bleed your brakes.

Audi A4 B7/B8: How to Replace Brake Line

Materials Needed

  • Wrench
  • Rag
  • Bottle
  • Flashlight
  • Hose
  • Brake line
  • Brake fluid
  • Flare nut wrench

When working with brake lines, we highly recommend investing in a set of flare nut wrenches. They have a shape specifically suited for brake lines, and will prevent possibly rounding off any fasteners in the braking system.

Step 1 – Locate the bad line

Before you start replacing brake lines, make sure you know exactly where the leak is coming from, and make sure it's the only line leaking. The last thing you want is to replace a line, bleed your brakes, then find out you have another leaking line, in which you will have to bleed your system all over again.

audi a3 a4 b7 b8 brake line fluid replace change remove how to
Figure 1. Locate the leaking brake line.

Step 2 – Remove brake line

Use your flare nut wrench to loosen the line's nut. Expect spillage, so if you're not ready with the new line, plug the other end of the line that's still connected to your brake system to avoid too much mess.

audi a3 a4 b7 b8 brake line fluid replace change remove how to
Figure 2. Remove brake line.

Step 3 – Install new line

Before installing the new line and tightening its nut, be sure to route it the same way the old one was routed. This will prevent it from moving around and touching a moving part or contacting the chassis. After you route it properly, tighten the nut, wipe down the fluid, and make sure the is no leaking fluid from the connection.

audi a3 a4 b7 b8 brake line fluid replace change remove how to
Figure 3. Use original clamps to route the line.

Step 4 – Bleed the brakes

Some say you can only bleed the caliper where you removed the line from, but it's recommended you bleed your whole brake system. When bleeding brakes, the goal is to work from the caliper furthest from the master cylinder, and work your way towards it. This means going in the following order: passenger-rear, driver-rear, passenger-front, and driver-front.

Locate the bleeder screw on each caliper, then connect the clear hose to it, and connect the other end of the hose to a bottle. Ask a friend to pump the brakes a few times, then ask them to keep it pressed down. Loosen the bleeder screw on the caliper with your wrench, and watch for the draining fluid. Close the bleeder after the few seconds. Repeat this process several times until you stop seeing bubbles. Repeat the process for the other calipers, but be sure to top off the master cylinder with fluid between each caliper. If the fluid in the caliper gets too low, you will have to start the bleeding process all over.

AUDI A3 A4 BLEED BRAKES BRAKE FLUID CHANGE REPLACE
Figure 4. Bleed all four calipers.

(Related Article: How to Change Brake Fluid - AudiWorld)

Related Discussions