5 min read

Green Brake Fluid - What Does It Mean?

After ages of deferring this very important task, you finally decided to check your brake fluid. Something doesn’t quite seem right though, does it? The fluid is green so you must be wondering what this could possibly mean. Well don’t get flustered, this article will explain what that green fluid means, and what you can do to prevent it from ever happening again.

Amie-Lynn Mitchell

First, let's learn what brake fluid is, and why it’s an integral part of your car functioning properly. 

Brake fluid is a common name for what is more correctly known as hydraulic fluid. This means that it is not just used to create friction between brake pads and a rotor (as in a drum brake system), but also to generate hydraulic pressure which pushes the brake pads against the rotor.

What does brake fluid do?

Brake fluid is the liquid chemical solution utilized in modern automobile hydraulic braking systems. It helps to stop your car by transferring the pressure from your foot on the brake pedal to the brake pads. The brake pads then press against the rotors, slowing down or stopping the car. It would take a lot more force and pressure to stop your automobile manually without brake fluid!

How long before I have to change my brake fluid?

Vehicle fluids have a standard life and will need to be replaced at certain intervals. How often you replace them depends on the vehicle manufacturer, driving style, and type of fluid used.

It usually needs to be replaced every two years or 38,000 kilometers, whichever comes first. If you drive in a very dusty, dirty environment, it is recommended that vehicle owners replace the fluid every year. In even more severe conditions, vehicle owners should change it every six months or 19,000 kilometers.

What color is brake fluid?

It is typically clear with a slight yellowish tint, depending on what kind of brake pads are used in the vehicle the fluid's age, and the brand. The color can certainly change as well if there have been any problems with the brake system.

How do I check brake fluid?

  • Checking it is a simple process that can easily be done at home. All you need is a rag, some engine degreaser or brake cleaner, and a funnel. Make sure your car is parked on a level surface and that the engine is turned off before you start.
  • Open the hood of the car and locate the brake master cylinder. The brake master cylinder is usually located on the driver's side of the engine compartment, near the firewall.

  • Check fluid level - The fluid level in the master cylinder should be between the minimum (MIN) and maximum (MAX) fill lines. The ideal fluid level is at or near the maximum (MAX) line. If it is not then you will need to top up your fluid levels with the vehicle manufacturer's recommended type of brake fluid.

    If your vehicle has an ABS system fitted it is important to make sure that your vehicle manufacturer recommends you use one made for anti-lock braking systems. If the vehicle does not have an ABS system fit then you can use a normal type.

  • Check fluid color - If it is green and/or contains glycol ether, it could be contaminated and should be checked by a professional for safety concerns.

Why is my brake fluid green?

If you have discovered that your brake fluid IS green, the most likely reason is that it has been contaminated by the fluid chemical components breaking down and attacking the brazed joint in the brake tubing. To put it a bit simpler, if copper levels are high enough in the fluid, the fluid will typically turn green. This is often caused by brakes that are not checked regularly enough or by the incorrect replacement of brake pads.

Another reason the fluid could turn green is that moisture has infiltrated the system. The fluid is hygroscopic, meaning it attracts and holds water molecules. As the water content in it increases, the boiling point decreases, which can lead to brake fade – a condition where the brakes don't work as well as they should because they've overheated.

Is this dangerous?

If your car's fluid turns a color other than what is typical for the type of brake system you have (most commonly, clear), it is definitely a cause for concern.

What to do next?

Generally, brake fluid is able to be flushed and refilled. The first thing you need to do is find a brake specialist who can test the integrity of your vehicle's hydraulic braking system. They will determine what's causing the green fluid and whether it needs new parts. If no damage has been done, then the vehicle should be fine after a fluid flush and refill.

However, if the brakes have been compromised, it's important to take your vehicle in for repair as soon as possible. Continuing to drive with contaminated fluid can lead to serious and expensive damage.

Be sure to keep an eye on your fluid levels, and change them according to your vehicle manufacturer's guidelines. Additionally, have your vehicle serviced regularly to avoid fluid contamination in the future.