Audi Q5: Brake Fluid Leak Causes & Diagnosis

Your Audi Q5’s brake system is the most important safety feature on the vehicle. Without a reliable braking system, it is dangerous to keep driving your Q5. A brake fluid leak is a serious problem. It is usually caused by a failure of a seal, brake line, master cylinder reservoir, and a few other issues.

When brake fluid leaks out, air enters the system. This will decrease the stopping power of your Q5. Once enough air enters the system, your brakes will no longer work.

Audi Q5 Brake Fluid Leak Causes

There can be a small fluctuation in the amount of brake fluid held by the master cylinder as disc brakes wear down. The piston will rest further from the caliper, and more fluid will stay in the system. This is not a leak, but it is worth pointing out, since it can appear to be one.

There are a number of issues that can cause your Q5’s brake system to leak fluid. Here are the most common ones.

1. Bleeder Valve

Depending on the year and options selected, your Q5 may have four wheel disc brakes, or it could have drum brakes on the back. Both types of brakes use bleeder valves to get air out of the lines.

These valves can be damaged or stripped out, allowing brake fluid to exit the brake system.

2. Brake Line

Brake lines connect all four brakes and the master cylinder. They can be made out of both rubber and steel. They can fail, particularly the rubber ones.

3. Piston Seal

Disc brakes calipers utilize pistons to press the brake pads into the disc. The piston seal keeps the brake fluid from exiting the caliper when the brakes are pushed. These seals can fail over time. If your Q5 has been parked for a very long time, this is one of the more common places a leak will occur.

4. Wheel Cylinder

On drum brakes the wheel cylinder takes the pressure from the brake fluid (when the brakes are pressed) and uses it to move the shoe into the drum. If your Q5 is equipped with drum brakes, this is a common failure point.

Take a look at the rear wheels, you may find brake fluid all over one of them (on the back part). That’s a pretty good indication that the wheel cylinder is bad.

Bleeder Valve on Wheel Cylinder

5. Fluid Reservoir

Attached to your master cylinder, there is a fluid reservoir. It holds extra brake fluid. Many of these are made out of plastic and can crack and leak brake fluid.

Audi Q5 Brake Fluid Leak Diagnosis

Finding a brake fluid leak takes time and patience, but isn’t the most difficult job in the world. Knowing a few things about how your Q5’s brake system works can make the job a lot easier.

Here’s a great video on how to compartmentalize and quickly find where the fluid leak is actually coming from.


Driving your Q5 with leaking brake fluid is very dangerous. If you can’t find it, have a mechanic take a look at it and fix it for you. Afterwards, make sure that you monitor your fluid level to make sure that the leak was fixed.

    Jason on Mazda 6 P0320: Meaning, Causes, & Diagnosis January 27, 2022

That is RIDICULOUS, Cheryl. You can’t get anything right now.

RECALLS! January 2022 Jason, “MAZDA6 shuts down while driving” fuel pump not monitored, may be no engine light etc. SEE…

I think it’s a 15 pin plug and two wires change on the plug fro 95 to. 97 it’s a…

I have a 2007 h3 hummer base model. Had transmission rebuilt (Pro).My problem is that when it gets around 35…

Is this the same John Watterson who once owned an ’84 VW Rabbit and an ’89 VW Fox?