How To Diagnose a Brake Fluid Leak And Am I Going to Crash?

Out of all the fluids that could be leaking from your car, brake fluid might be one of the hardest to diagnose. It doesn’t have a color, it doesn’t have a particularly strong smell, and it might not even show up under your car if the leak is small enough. It’s a recipe for a headache.

Brake fluid is pushed at high pressures through small hoses and lines in your vehicle and helps your brakes physically clamp down to provide the friction you need to stop. Because of that high pressure and because brakes are one of the most frequently used components of your vehicle, it’s easy to imagine how leaks might occur. 

Damaged hoses, overworked brake components, and more can all cause brake fluid to escape its high-pressure prison. What can you do to diagnose the issue and what will it take to fix it? The Drive’s editors have those answers and more, but you’ll have to put up with a few bad jokes along the way. Sorry, not sorry.

Your car’s brakes, no matter the type, are part of a hydraulic system. Pressure pushes brake fluid through lines and on to the brakes themselves, where the pressure forces the calipers to squeeze brake pads onto the rotors.

Brake fluid is usually stored in a reservoir in the engine bay. There are different types of brake fluid, each with its own ideal operating temperature ranges and price tag. They include DOT 3, DOT 4, DOT 5, and DOT 5.1. Most vehicles use DOT 3, which has a boiling point of 205 degrees Fahrenheit. Some use the other variations, but they are specifically designed to run those fluids, and cannot have other types of brake fluids mixed in.

Unlike many of the fluids under your hood, brake fluid is colorless, so there’s no easy way to identify a puddle of brake fluid on your garage floor. A good way to investigate is to check the consistency of the fluid leak you’re seeing. Brake fluid has a consistency close to that of vegetable oil.

Even if you’re not seeing fluid where you parked your car, you could still have a leak. If fluid is escaping the system somehow, you’ll notice a drain on the levels in the reservoir and may even see a warning light in your dash when the fluid levels get low enough. The brake pedal may also go to the floor and not return after lifting your foot.

There are quite a few reasons why your brake fluid might leak.

If there’s a hole or other damage to the brake lines, the fluid won’t be able to reach its destination without leaking.

Over time, the heat generated by braking will cause the seals in the calipers to break down, which can allow brake fluid to escape.

The master cylinder is made up of valves and seals that can wear over time and allow fluid to leak.

Some parts of your vehicle’s ABS (anti-lock braking system) carry and hold high-pressure brake fluid. Over time, the seals and components of the reservoirs can wear and leak.

Get educated!

The master cylinder is the first component in the braking system after the brake pedal. When the driver presses the brake pedal, it pushes a piston into the cylinder, which pushes brake fluid through the lines.

Anti-lock brakes are a safety feature that allows drivers to maintain control of the vehicle, even under extreme braking conditions. If the wheels are allowed to lock when the brakes are pressed hard, the car will skid and continue traveling in the same direction it was before. Anti-lock brakes help remedy this issue by pulsing the brakes on and off quickly to allow a slight bit of wheel rotation. That rotation prevents a total lockup and allows the driver to remain in control.

Hydraulic systems use pressurized fluids to move components, which in this case are parts of the braking system. Brake fluid provides the hydraulic pressure needed to operate the brakes.

While The Drive’s how-to guides are detailed and easy to follow, no vehicle is created the same, and not all auto maintenance or repair tasks are easy to accomplish on your own. That’s why we’ve partnered with YourMechanic and their network of mobile automotive technicians to offer our readers $10 off a $70 or more service call when you use promo code THEDRIVE.

You’ve got questions, The Drive has answers!

A. It’s technically possible, but it’s never something we’d recommend. You might have braking power one moment and the next you could be skidding into an accident. There’s also the possibility of damaging other parts of your vehicle if the brakes don’t have the fluid they need to function properly.

A.The costs will depend on what’s actually wrong with your brakes. If it’s a simple fix of a brake line or component, it could cost between $100 and $300 to fix. If it’s the brake master cylinder, it could cost up to $400 on its own to fix.

A. The best way to prevent leaks is to keep up with maintenance and inspections of your braking system. Ignoring problems tends to lead to bigger problems, which is especially true for leaks.

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Jonathon Klein: Twitter (@jonathon.klein), Instagram (@jonathon_klein)

Tony Markovich: Twitter (@T_Marko), Instagram (@t_marko)

Chris Teague: Twitter (@TeagueDrives), Instagram (@TeagueDrives)

You’ve got plenty of options when it comes to products to help you diagnose and fix brake fluid leaks, so we won’t overload you with a sales pitch here. What we will do is show you a few of The Drive’s favorite products that we feel are affordable, useful, and well-reviewed.

Prestone AS400 DOT 3 Brake Fluid

Ares Two-Liter Manual Brake Fluid Bleeder

Innova CarScan Code Scanner

Pro-Lift Jack Stand

Got a question? Got a pro tip? Send us a note: guidesandgear@thedrive.com