Time

15-30 minutes

Complexity

Beginner

Cost

Less than $40

Introduction

Don't risk driving with compromised brakes. We'll show you how to check brake fluid properly and identify when it needs to be replaced.

Here’s another piece of car maintenance advice that I didn’t listen to when I got my first car, but now has become a ritual: Check your brake fluid every three to four months. Even if your brakes are working fine, it’s good to do a visual check to catch any issues before they cause damage or disrupt your brakes’ proper functioning.

The good news is that it is relatively easy to check the condition of your brake fluid. Here’s how!

When to call a pro

If the brakes push all the way down and have lost their sensitivity, this might mean something is wrong with your brake fluid. It could be that it is not at the optimal fluid level or that the fluid has been contaminated.

Brake fluid contains a main ingredient along with protective additives. The main ingredient in brake fluid doesn’t degrade, but the additives do. This leads to contamination. The most important additive is a corrosion inhibitor. The corrosion inhibitor prevents internal rusting of steel brake lines, calipers and ABS (antilock brake system) components. Once the inhibitors are exhausted, even minute amounts of moisture can cause dangerous and costly corrosion, which will decrease the stopping power of the brake fluid. So, if your brake fluid smells burnt or is no longer transparent, it probably means it’s contaminated.

Either way, if your brakes are mushy or need to be pressed to the floor to work, don’t take a risk—have your car towed to the nearest auto mechanic.

Here are some general guidelines for regularly checking brake fluid to catch issues before they cause harm.

Tools Required

  • Funnel
  • Gloves

Materials Required

  • Brake fluid
  • Brake fluid test kit

Project step-by-step (8)

Step 1

Open the hood and identify the brake fluid reservoir

The brake fluid reservoir is usually plastic and clear or semi-translucent. This allows you to visualize the brake fluid levels without removing the cap. The reservoir is usually in the back of the engine bay and, depending on the car, could be by the driver’s or passenger’s side. If you have difficulty finding it, check your manual.

Open The Hood And Identify The Brake Fluid ReservoirTMB STUDIO
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Step 2

Check brake fluid level

On the side of the reservoir, there should be a maximum and a minimum indicator line.

  1. First, wipe the reservoir so you get a clear reading.
  2. If the fluid level is at or near the minimum level, the brake fluid should be topped off and then taken to a reliable mechanic. Low brake fluid could mean worn brakes or a leak.
    1. When topping off brake fluid, refer to your manual on which brake fluid to purchase.
    2. Be sure to use a funnel when adding brake fluid. If it spills, it needs to be cleaned up immediately. Brake fluid is toxic. Wash your hands if exposed, and wipe it off of painted surfaces immediately.
    3. Fill to the maximum line.
    4. Secure the cap tightly.
  3. The level is good if the fluid level is at or around the maximum line.

Check Brake Fluid LevelTMB STUDIO
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Step 3

Brake fluid color chart

If levels are fine, next step is to check the color of the fluid by removing the cap.

Normal colors:

  • DOT 3 Brake fluid: Comes in clear or yellow, but will sometimes have blue, green and red shades.
  • DOT 4 Brake fluid: Comes in light yellow or crimson red shades.
  • DOT 5 Brake fluid: Comes in purple shades.
  • DOT 5.1 Brake fluid: Comes in clear/yellow, and sometimes blue shades.

Signs of additives wearing out and fluid is contaminated and therefore needs to be taken to a mechanic:

  • Darkened fluid
  • Greenish tint
  • Murky/muddy

How To Check Brake FluidFAMILY HANDYMAN, GETTY IMAGES
FAMILY HANDYMAN, GETTY IMAGES

Step 4

Brake fluid strip test

Recently, my car fluid had a light green tint to it, so I worried that I needed to take it in and have my brake fluid replaced. The good news is that I could test the fluid myself and see how contaminated it was. The type of test I used indicates how much copper is in the system, which, if present, implies that the corrosion inhibitor is worn out or wearing out. If worn out, it will no longer protect the steel brake lines from rust, releasing copper, iron and zinc into the brake fluid.

So, if it isn’t clear that your fluid is bad and you are concerned, you can take the extra step and test the fluid yourself using a brake test kit.

Brake Fluid Strip TestTMB STUDIO
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Step 5

Have the kit ready before opening the lid

If you need to test your brake fluid, ensure you have your test kit set up and ready before opening the lid. Any time the brake fluid lid is removed, it is exposed to humidity, which can contaminate it.

Step 6

Dip the brake fluid test strip

To check your brake fluid, put on plastic gloves, remove the reservoir cover, and dip a strip into the fluid.

Dip The Brake Fluid Test StripTMB STUDIO
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Step 7

Compare the strip indicator to the guide

The guide identifies the copper levels and whether it’s time to change the fluid. Take it to an auto mechanic to replace your brake fluid if the strip’s color falls in the “required service” category. My brake fluid read at 30, so it didn’t need immediate service. However, if, like my car, the test indicates some contamination—just not enough for immediate service, continue to monitor your fluid coloration. This could be a sign that the corrosion inhibitor is degrading, which is allowing steel brake lines, brake calipers and ABS (antilock brake system) components to rust. If this is the case, the brake fluid must be replaced soon.

My copper levels are at a 30, which means it doesn’t need immediate service but will need to be monitored.

Compare The Strip Indicator To The GuideTMB STUDIO
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Step 8

FAQs

How often do I need to change my brake fluid?
This varies depending on the vehicle’s model. So, it’s best to review the owner’s manual to determine the frequency. But most car manufacturers recommend a complete brake fluid flush every two years or 24,000 miles.

How does Brake fluid work?
Essentially, brake fluid takes the pressure from the depressed foot pedal and sends it to the front and rear brakes, which then stop the vehicle.

How do you know if brake fluid is low?
Other than a visual check of the levels in the reservoir, other indicators brake fluid is low include:

  1. The vehicle needs additional pressure on the brake pedal for it to stop.
  2. The brake light on the dashboard is on.
  3. The brake pedal, when pressed, feels spongy.

If any of these symptoms occur, it means your brakes are in trouble, and you should see an auto mechanic immediately.