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How To Check Brake Fluid in Your Car and Refill if Needed

Modern vehicles are more complicated than those of decades past. Still, most manufacturers make it easy for owners to perform routine maintenance tasks on their own. If you like keeping your car clean and ready to roll, you’re probably motivated enough to tackle the small things on your own without taking it to a mechanic for everything. Things like changing your oil and replacing your vehicle’s air filters can be done with little automotive knowledge and few, if any, tools. Likewise, it’s easy for almost anyone to check their car's brake fluid with two hands and less than 10 minutes of free time.

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10 minutes

What You Need

  • Owners manual

  • Two clean rags

  • Fresh brake fluid appropriate for your vehicle

  • Screwdriver (for older-model cars)

  • Plastic gloves (optional)

  • Brake fluid test strips (optional)

how to check your cars brake fluid vehicle engine motor closeup

How To Check Brake Fluid Level

Checking your car's brake fluid level is almost as easy as checking your windshield washer fluid. If you can open your vehicle’s hood and unscrew a cap, you’ve got all the skills you need. A word of caution before getting started: Brake fluid can be highly toxic. Avoid getting it in your eyes, and be sure to wash your hands thoroughly after checking the brake fluid level. It’s also corrosive, so avoid spilling any on your vehicle’s finish or engine components. Ready to check your vehicle’s brake fluid level? Let’s get started!

Step 1: Open your vehicle’s hood. Find the master cylinder — a small, capped reservoir usually located near your vehicle’s firewall at the back of the engine compartment. It’s typically on the driver’s side of the engine bay in front of where your car's brake pedal is mounted. If you’re having trouble finding it, consult your owners manual.

Step 2: Check the brake fluid level. Most newer vehicles (approximately mid-1980s and later) have a translucent plastic reservoir, so it’s easy to see the “full” line without removing the screw-off cap.

Most older cars (prior to the early 1980s) relied on a metal reservoir topped with a spring-loaded clamp. In this case, use a shop rag to wipe away any dirt from around the cap. Even a small amount of debris inside the master cylinder can damage your car’s delicate braking system. Use a screwdriver or good multi-tool to pry the spring-loaded clamp to one side and lift the cap. Look for the “full” line inside.

Step 3: No matter the age of your vehicle, add brake fluid if the level is low. Some vehicles have a dual-chamber reservoir, in which case you should fill both to “full.” Wipe away any spilled or excess brake fluid immediately. Also, note that if your reservoir is empty or excessively low, this likely indicates an issue with your brake system. Consult a mechanic immediately as your vehicle may be unsafe to drive.

Step 4: To continue checking the quality of the brake fluid, move to the section below. If not, you’re all done. Just replace the reservoir cap.

How To Check Your Car's Brake Fluid

Brake fluid contains additives to inhibit rust and corrosion of critical brake line components — namely the calipers, steel brake lines, and antilock brake system. While you’re under the hood checking the master cylinder, it’s important to note not only the level but also the quality and pH balance of your car’s brake fluid. This can be a little trickier than merely checking the level. Still, it’s straightforward with a readily available brake fluid test kit purchased from any automotive store or online retailer. With the master cylinder cap still off, follow these two additional steps.

Step 1: Always don disposable plastic gloves to check brake fluid.

Step 2: Open the brake fluid test kit and remove a single disposable strip. Dip the strip into your vehicle’s brake fluid. Shake off any excess. Wait 60 seconds.

Step 3: Compare the color on the strip to the guide/chart included with your brake fluid test kit. This will indicate when and if it’s time to change the brake fluid.

how to check your cars brake fluid racing brakes closeup

When To Schedule a Brake Fluid Flush

Like changing your oil and replacing your car’s air filters, when to schedule a complete brake fluid flush depends on your driving habits and your car’s year, make, and model. Most manufacturers recommend this service every 24 months or 30,000 miles, though this can vary. Again, consult your owners manual to be sure. Also, know that this is just a guideline. The only way to be sure is to check your car’s brake fluid quality is with a proper testing kit or visit a qualified mechanic.

Know the Warning Signs of Low Brake Fluid

During regular operation, your vehicle should not lose brake fluid. Levels may drop slightly as brakes wear over time. But if the level has fallen significantly since your last fluid level check or full service, it’s time to see a mechanic. Minor issues are much easier and less costly to repair than dealing with total brake failure down the road.

Know Your Brake Fluid Type

Every manufacturer recommends a specific type of brake fluid for their vehicles. This is usually — though not always — DOT3 or DOT4 and noted on your vehicle’s brake fluid reservoir cap. Consult your owners manual if you can’t find the recommended brake fluid type. Never mix and match brake fluid types or use a brake fluid that’s not designed for your vehicle’s brake system.

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