How To Check Brake Fluid (2024)

ByNina Bricko

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.

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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.

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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 orcrimson 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

FAMILY HANDYMAN, GETTY IMAGES
FAMILY HANDYMAN, GETTY IMAGES

Step 4

Brake fluid strip test

Recently, my car had a light green tint to it, so I worried that I needed to take the car in and have my brake fluid replaced. The good news is that I was able to 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 it’s worn out, it will no longer protect the steel brake lines from rust, which releases 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.

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Step 5

Have the kit ready before opening the lid

If you need to test your brake fluid, make sure to have your test kit set up and ready before opening the lid. Any time the brake fluid lid is taken off, the fluid 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.

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Step 7

Compare the strip indicator to the guide

The guide identifies the level of 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, which means 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 will need to be replaced soon.

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

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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, there are other indicators that brake fluid is low:

1. The vehicle needs additional pressure to the brake pedal in order 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.