AudiWorld Forums

Audi A4 B7/B8: How to Replace Brake Fluid

The brake fluid can start losing its boiling point, which can be rather dangerous in the Audi A4. Read on to learn how to replace the fluid.

By Bassem Girgis - March 23, 2016

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

Over time, the brake fluid can start degrade, resulting in a lowered boiling point, and the more it drops, the more dangerous it can get. The boiling point of brake fluid refers to the temperature at which the brake fluid will break down and begin to absorb moisture and accumulate air, which, in a hydraulic system, is bad. Basically, if you push the brakes really hard on old fluid, you're going to experience an increasingly soft, sinking pedal and heavily diminished braking capacity. You can press down that pedal as much as you want, the car is not going to slow down, which is terrifying. This guide will show you the whole process of draining the brake fluid, refilling it, and bleeding the system. Read on to learn how to replace the brake fluid in your Audi A4.

Audi A4 B7/B8: How to Replace Brake Fluid

Materials Needed

  • Turkey baster
  • Wrench
  • Clear hose
  • Bottle
  • Brake fluid

Step 1 – Remove fluid from master cylinder

Use your turkey baster to suck the old brake fluid out of your master cylinder. Leave a little bit of fluid in the master cylinder, as little as half an inch of fluid. This will prevent air from going into the system.

AUDI A3 A4 B7 B8 BLEED BRAKES HOW TO BRAKE FLUID CHANGE REPLACE
Figure 1. Suck fluid out of master cylinder.

Step 2 – Refill master cylinder

Add fresh, new brake fluid on top of the old fluid, and fill the master cylinder to the max line.

AUDI A3 A4 B7 B8 BLEED BRAKES HOW TO BRAKE FLUID CHANGE REPLACE
Figure 2. Fill master cylinder with fresh fluid.

Step 3 – Bleed the brakes

Now you need to bleed the brakes to get the old fluid out, and make sure there is only fresh fluid in your system. When bleeding brakes, you need to start at the point 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 last.

Locate the bleeder screw on the back of each brake caliper. Install the clear hose on top of the bleeder screw, and install the other end into a bottle, then ask a helper to pump the brake pedal a few times. With the brake pedal pressed all the way down, loosen the bleeder screw with your wrench, then watch the fluid draining out. Tighten up the bleeder again and repeat this process of pumping the pedal, holding it down and opening the bleeder. Do this until clean, air bubble-free fluid is coming out of the caliper. It's critical that you add more fresh fluid in the master cylinder between bleeding each caliper. If the master cylinder gets too low, you may need to start the whole bleeding process again because air will be induced into the system.

AUDI A3 A4 B7 B8 BLEED BRAKES HOW TO BRAKE FLUID CHANGE REPLACE
Figure 3. Bleed the four calipers.

Related Discussions