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Brake Fluid Leaks: All You Need To Know (2021 Guide)

February 19, 2021

Concerned that you have a brake fluid leak?

Here’s a scenario no car owner wants to be in:

Your car isn’t slowing down as quickly as it used to. Additionally, when you press down on your brake pedal, it drops to the floor with minimal resistance. 

Naturally, you wonder what’s wrong, and take a look at the underside of your vehicle and spot an unfamiliar, yellowish puddle of fluid. 

Looks like something’s wrong.

But what is it? 

Any leak from your car can be cause for concern. 

And judging by the looks of it, it could be a brake fluid leak — which can be dangerous. 

But don’t worry.

In this article, we’ll show you how to detect a brake fluid leak, what causes it, and the best way to solve brake problems. 

This Article Contains

(Click on a link below to jump to a specific section)

What Is Brake Fluid?

Brake fluid is a type of hydraulic fluid that’s used in your car’s brake system.  

When the brake pedal is pressed, brake fluid acts as a conduit to transmit pressure to each tires’ braking mechanism. 

Why is a fluid used? 

Fluid is non-compressible and any pressure exerted on the fluid is equally distributed. 

This way, an equal force is delivered from the brake pedal to all four tires simultaneously. There can’t be any air in the brake line as air bubbles can affect the hydraulic pressure of the brake fluid, which will change how your brakes react. 

Think of it this way:

It’s kind of like water in a straw. 

If the straw is full of water and you blow from one end — the water moves evenly together. But if there are air bubbles in the straw, the water doesn’t move evenly anymore as the air bubbles create a break in the pressure distribution.

So, what happens when there’s a brake fluid leak?

You lose brake pressure, as a leak not only reduces the fluid in the brake line, but also introduces air into your brake system. This reduced pressure in the hydraulic brakes then translates to problems in stopping your vehicle. 

So, how can you tell if you have a brake fluid leak?

4 Common Symptoms Of A Brake Fluid Leak

There are several common red flags to spot a brake fluid leak. 

In general, if your vehicle’s brake performance is compromised, then there’s likely an issue somewhere in your braking system.

You just have to determine if it’s from worn brake pads, brake fluid leakage, or another problem.

Here are the signs typically associated with a brake fluid leak:

1. The Brake Warning Light Flashes

This is a clear indicator that something’s wrong with your brakes.

When the brake warning light glows, it can mean a handful of things:

As there are so many potential causes, it’s always best to take your car to a mechanic when you see your brake warning light flashing.

2. There’s A Puddle of Fluid Under Your Car

This is the most obvious sign of a brake fluid leak.

However, not every puddle of fluid under your car indicates a brake fluid leak.

Remember, your vehicle uses all types of fluids for it to function. A puddle under the car can indicate many things, so don’t immediately panic. Sometimes it’s just condensation from your air conditioner, especially if you’ve had it running on a hot day.  

That’s why the best thing to do is have a good look at the fluid. 

The color can indicate what it is:

However, paying attention to the location of the puddle is just as important as taking note of the color. If your vehicle is leaking brake fluid, the puddle’s location can indicate which brake system component is causing problems.

For example:

3. A Mushy Feeling When The Brake Pedal Is Pressed

Does your brake pedal suddenly feel less resistant than normal? Perhaps it feels mushy or squishy?

This usually happens if there’s an issue with the master cylinder, brake booster, or a low brake fluid level in the reservoir. However, air in the brake line resulting from a leak can also lead to a soft brake pedal feel.

You can pump your brakes several times to build up hydraulic pressure. If there’s still no pressure buildup, then you likely have a brake leak.

4. The Brake Pedal Drops To the Floor

If your brake pedal sinks all the way down to the vehicle floor when you step on it, you could have a serious problem.

If this happens before you start on your trip, don’t drive.

It’s a critical warning sign that can indicate a massive leak or a problem with the master cylinder. There’s a good chance that the brake fluid level is simply too low for efficient brake function. 

If brake issues like this happen when you’re driving, the best thing you can do is to use gear-braking. Downshift your gears to slow the car using the engine, and find a safe, stopping spot as soon as possible.

When you’re moving slowly enough, you can apply the parking brake gently to roll to a stop. Don’t pull the parking brake when you’re still at speed, as this can send you into a spin. 

Where To Check For A Brake Fluid Leak

If you’ve noticed any of the symptoms mentioned, you can carefully pop the hood and check the brake fluid reservoir to confirm a leak. A severe leak will cause very low brake fluid levels in the reservoir. If you’re having trouble locating the brake fluid reservoir, you can refer to your vehicle’s owner’s manual.

If the brake fluid level looks fine, there’s still a possibility that you have a small leak somewhere that’s letting in air, causing you to lose brake fluid at a slower rate.

So, where do you search for these small leaks?

Typical automotive brake systems can be divided into the following sections:

While you can check these sections for a leak, it’s always better to let professional brake technicians do the job.

Why?

Brake fluid leaks can occur due to several different reasons — some of which require checking parts that the average car owner may not be familiar with. Professional mechanics are far more well-versed with brake inspection and have the necessary equipment to deal with these issues.

With that being said, here’s a look at some of the most common causes of a brake fluid leak:

6 Common Causes Of Brake Fluid Leakage

Here are some of the most common culprits of brake fluid leaks that your technician can help you find:

1. Damaged Brake Master Cylinder Reservoir

The brake master cylinder reservoir is typically made of plastic and can become brittle from heat exposure. When this happens, it’ll eventually crack, causing brake fluid to seep out and flow down the back of the engine.

2. Failed Piston Seal 

Brake components like the master cylinder, disc brake caliper, or drum brake wheel cylinder all function through a piston.

The piston is a moving part that’s activated by brake fluid. It has seals that help contain the fluid, and these can be damaged from regular wear and tear, causing a leak. 

3. Worn Out Brake Pads, Shoes, Rotors And Drums

Brake pads, rotors, brake shoes and drums can also wear down over time. 

When this happens, it’s possible for the caliper piston or wheel cylinder piston to become hyperextended, breaking the piston seals and leak fluid. 

Also read: Explore the differences between the ceramic and semi-metallic brake pad to determine which one suits you.

4. Damaged Brake Lines or Brake Hose

Brake lines and hoses are designed to withstand most road and weather conditions. But they’re subject to rust, pitting, and tears over time.

A broken brake line, a tear in the brake hose, or damaged brake line fittings can all lead to brake fluid leaks.

5. Damaged or Loose Bleeder Valve

Each brake caliper or brake drum has a bleeder valve (or bleeder screw) used to “bleed brakes,” — which allows air to be expelled from the steel brake lines. 

If the bleeder valve gets damaged or knocked loose, it can cause brake fluid to leak.

6. Faulty ABS Module

Some parts of the ABS pump in your brakes carry and hold high-pressure brake fluid. Unfortunately, your ABS brake reservoir seals can wear down over time – leading to a brake fluid leak.

At this point, you or your mechanic should have figured out the source of your brake fluid leak. 

The next question is — how much will the repair cost you?

The Average Cost To Fix A Brake Fluid Leak 

The cost for fixing a brake fluid leak depends on your vehicle’s make and model, and which component is causing the leak.

To give you an idea, here’s a rough cost breakdown:

Vehicle componentAverage Replacement Cost
(including parts + labor)
Master cylinder leak$400-$550
Brake line leak$150-$200
Brake caliper leak$525-$700
Rear drum cylinder leak$150-$200

While it’s possible to fix a brake fluid leak by yourself, it’s not recommended unless you’re a trained automotive professional. It’s always best to hire a mechanic to ensure repairs are performed correctly.

The Best Way To Get Your Brake Fluid Leak Fixed

If you’re looking for a mechanic to help you diagnose and repair a brake fluid leak, make sure that they:

RepairSmith is the most convenient car maintenance and repair solution that offers all of the above and more. They are currently available in Arizona, California, Nevada, Oregon, and Texas.

Here are the benefits of having RepairSmith as your vehicle repair solution: 

To get an accurate estimate of what your brake fluid leak will cost, simply fill out this online form.

Never Ignore That Puddle Under Your Car

Most car owners don’t usually check under their car for leaks — which can make diagnosing a brake fluid leak difficult. However, if you’re facing any of the symptoms we mentioned, remember to get your car checked out immediately.

And if you need to get your car repaired, look no further than RepairSmith.

All it takes is a few clicks to book an appointment, and an ASE-certified technician will show up at your driveway — ready to get you back on the road.

Get in touch today and let RepairSmith fix that brake fluid leak you’ve been worried about!