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Categories
Cars & Other Vehicles
Cars
Car Maintenance and Repair
Vehicle Fuels and Fluids
How to Check Brake Fluid Download Article Co-authored by Ed Beery
Last Updated: July 18, 2025 Fact Checked
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Checking the Brake Fluid Level
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Checking the Brake Fluid Condition
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Q&A
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Tips
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Warnings
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Things You'll Need
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This article was co-authored by Ed Beery. Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified. There are 11 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 403,799 times.
Your car's brake system is one of several automotive hydraulic systems. When you push down on the brake pedal, fluid is delivered through the brake lines from the master cylinder to the brake drums or discs, slowing the car through friction. To make the system work properly, you need to have enough brake fluid in the system, and it needs to be in good enough condition to do its job.
Steps
Method 1 Method 1 of 2:
Checking the Brake Fluid Level
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1 Open the car's hood.[1]XResearch source It's best to do this when the car is stopped on a level surface, with the engine cold.
2 Look for the master cylinder. On most cars, the master cylinder is located at the back of the engine bay, on the driver's side. There's a reservoir above the cylinder itself.[2]X Expert Source Ed BeeryAutomotive SpecialistExpert Interview Advertisement
3 Check the fluid level in the reservoir.[3]XResearch source On most newer cars, the reservoir is transparent, with lines marked "Min" and "Max"; the brake fluid level should fall between these lines. Cars older than the 1980s may have metal reservoirs, requiring you to remove the reservoir cap. (Newer caps screw on and off, while some older caps need to be pried off with a screwdriver.)
4 Add brake fluid to the reservoir if required. Pour the fluid carefully into the reservoir, wiping up any spills, as brake fluid is toxic and corrosive.[4]XResearch source
Use only the brake fluid with the DOT specification recommended in your owner's manual. There are three main specifications: DOT 3, DOT 4 and DOT 5, each having its own properties. It is possible to use DOT 4 brake fluid in some cars that call for DOT 3 fluid, but never the reverse, and DOT 5 brake fluid can be used only in cars that call for that specification. Note that most cars indicate the required brake fluid DOT at the reservoir cap.
This is also a good time to check how well the reservoir cap seals.
5 Replace the reservoir cap and close the hood.[5]XResearch source
If the brake fluid level is significantly below the "Min" or "Add" line, you should have your brakes inspected for excessive wear. As brake pads wear down, brake fluid can channel itself out of the brake lines into the calipers.[6]XResearch source
It is also possible to have the brake fluid reservoir full and not have the brake fluid reaching the master cylinder. If your brakes feel spongy even with the reservoir full, take your car to a mechanic.
Advertisement Method 2 Method 2 of 2:
Checking the Brake Fluid Condition
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1 Check the brake fluid color. Normally, brake fluid is brown. If the fluid looks dark or black, it may need to be replaced but further testing is needed.[7]X Expert Source Ed BeeryAutomotive SpecialistExpert Interview [8]XResearch source
2 Dip a chemical test strip into the fluid.[9]XResearch source As brake fluid ages, its corrosion inhibitors break down. Test strips check the presence of copper in the brake fluid; the higher the level, the more worn out the inhibitors are. One such test strip is Phoenix Systems' "Brake Strip Brake Fluid Test Strip"
3 Test for moisture content with an optical refractometer.[10]XResearch source Brake fluid is hygroscopic, which means that over time, it absorbs moisture from its surroundings. Moisture dilutes and weakens the effectiveness of brake fluid, which leads to braking systems components to corrode. In 18 months, brake fluid can have up to 3 percent water, which can lower its boiling point from 40 to 50 percent.
4 Evaluate the brake fluid's boiling point with an electronic tester. New DOT 3 specification brake fluid is to have a dry boiling point of 401 degrees Fahrenheit (205 degrees Celsius) and a wet boiling point of 284 degrees (140 degrees Celsius), while DOT 4 fluid is to boil at 446 degrees (230 degrees Celsius) dry and 311 degrees (155 degrees Celsius) wet. The lower the point at which the brake fluid boils, the less effective it is.
Your mechanic should have both an optical refractometer and electronic brake fluid tester to perform these tests for you as part of an automotive checkup.
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Community Q&A
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Question My brakes don't squeal but my pedal goes to the floor. What is the issue? Community Answer You may have bad linkage or the brake fluid may be low on a more modern car. Thanks! We're glad this was helpful.Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 6 Helpful 8
Question Should the engine be hot or cold when I'm checking the brake fluid? Community Answer It doesn't matter, although you might feel more comfortable if the engine is cold. Thanks! We're glad this was helpful.Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 3 Helpful 17
Question What color should the brake fluid be? Logic Johnson Lafontaine Top Answerer If it's new, it can be clear or amber. As it gets older, it will turn closer to brown. Thanks! We're glad this was helpful.Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 4 Helpful 11
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Tips
Most manufacturers specify times for when brake fluid should be replaced. Check your owner's manual for information specific to your make and model. Thanks Helpful 3 Not Helpful 3
One reason your brake fluid may be bad involves moisture. Brake fluid is hygroscopic - this means it absorbs moisture - from the breather hole in the master cylinder reservoir cap, from the rubber hoses, and possibly from the "new" bottle of brake fluid if the cap hasn't been kept on it. Thanks Helpful 2 Not Helpful 3
Submit a Tip All tip submissions are carefully reviewed before being published Name Please provide your name and last initial Submit Thanks for submitting a tip for review! Advertisement
Warnings
In addition to seeing your brake or ABS warning light come on, if your brake pedal feels too hard or spongy, goes down too far, makes noise, drags or pulsates, or if your car pulls to one side or gives off a burning smell while braking, take the car in for servicing. Thanks Helpful 24 Not Helpful 17
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Things You'll Need
Bottle of brake fluid
Funnel (optional)
Rag or paper towel
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↑ Ed Beery. Automotive Specialist. Expert Interview
↑ https://www.bothellwa.gov/592/Vehicle-Leaks
↑ https://www.bothellwa.gov/592/Vehicle-Leaks
More References (4)
↑ https://www.youtube.com/watch?v=xVHRpBn-yaA
Videos provided by Jon Olson
[1]
[2]
About This Article
Co-authored by: Ed Beery Automotive Specialist This article was co-authored by Ed Beery. Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified. This article has been viewed 403,799 times. 10 votes - 70% Co-authors: 15Updated: July 18, 2025 Views: 403,799 Categories: Car Brakes | Vehicle Fuels and FluidsArticle SummaryX
To check your vehicle’s brake fluid, start by opening the hood and finding the master cylinder, which is toward the back of the engine bay on the driver’s side. Then, look at the reservoir next to it and check if the fluid falls between the “Min” and “Max” lines on the container. If it’s below the minimum, carefully add more fluid. Also, check the color of the brake fluid to make sure it's brown and not black. If it looks black, you may need to replace it. For tips on how test your brake fluid if you think it needs to be changed, read on!Did this summary help you?YesNo
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Yes No Advertisement Cookies make wikiHow better. By continuing to use our site, you agree to our cookie policy. Co-authored by: Ed Beery Automotive Specialist 10 votes - 70% Click a star to vote Co-authors: 15Updated: July 18, 2025 Views: 403,799
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Co-authored by: Ed Beery Automotive Specialist This article was co-authored by Ed Beery. Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified. This article has been viewed 403,799 times. 10 votes - 70% Co-authors: 15 Updated: July 18, 2025 Views: 403,799 Categories: Car Brakes | Vehicle Fuels and Fluids Article SummaryX
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1 Open the car's hood.[1] It's best to do this when the car is stopped on a level surface, with the engine cold. 
2 Look for the master cylinder. On most cars, the master cylinder is located at the back of the engine bay, on the driver's side. There's a reservoir above the cylinder itself.[2] Advertisement 
3 Check the fluid level in the reservoir.[3] On most newer cars, the reservoir is transparent, with lines marked "Min" and "Max"; the brake fluid level should fall between these lines. Cars older than the 1980s may have metal reservoirs, requiring you to remove the reservoir cap. (Newer caps screw on and off, while some older caps need to be pried off with a screwdriver.) 
1 Check the brake fluid color. Normally, brake fluid is brown. If the fluid looks dark or black, it may need to be replaced but further testing is needed.[7] [8] 
3 Test for moisture content with an optical refractometer.[10] Brake fluid is hygroscopic, which means that over time, it absorbs moisture from its surroundings. Moisture dilutes and weakens the effectiveness of brake fluid, which leads to braking systems components to corrode. In 18 months, brake fluid can have up to 3 percent water, which can lower its boiling point from 40 to 50 percent. 
4 Evaluate the brake fluid's boiling point with an electronic tester. New DOT 3 specification brake fluid is to have a dry boiling point of 401 degrees Fahrenheit (205 degrees Celsius) and a wet boiling point of 284 degrees (140 degrees Celsius), while DOT 4 fluid is to boil at 446 degrees (230 degrees Celsius) dry and 311 degrees (155 degrees Celsius) wet. The lower the point at which the brake fluid boils, the less effective it is. 
Community Answer You may have bad linkage or the brake fluid may be low on a more modern car. Thanks! We're glad this was helpful. Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 6 Helpful 8 
Community Answer It doesn't matter, although you might feel more comfortable if the engine is cold. Thanks! We're glad this was helpful. Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 3 Helpful 17 
Logic Johnson Lafontaine Top Answerer If it's new, it can be clear or amber. As it gets older, it will turn closer to brown. Thanks! We're glad this was helpful. Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 4 Helpful 11