What causes Brake Fluid Leaks and How to Fix it?

The braking system consists of several components. These components include brake pads, brake shoes, brake drums, brake master, brake booster, ABS, brake calipers, and brake lines. These components have to work in harmony to bring your car to a complete stop when you depress the brake pedal.

But without the brake fluid, all these components won’t actualize their single aim of bringing the vehicle to a complete halt. This is why you need to be cautious of brake fluid leak and fix them before it causes severe damage to other system components. So, in this article, we’ll discuss at length brake fluid leak color, signs, causes, and how to fix it.

What causes brake fluid leak?

brake fluid leak fix

Before discussing the causes, what are brake fluid leak symptoms that you should watch out for? Several red flags indicate brake fluid leaks. Here are the signs you should watch out for when you suspect a brake fluid leaks;

  • Brake fluid dripping under your vehicle
  • Mushy or spongy brake feel when you depress the brake pedal
  • The brake pedal goes to the floor when you step on it
  • A brake warning light appears on the instrument cluster

We’ve outlined the common causes of brake fluid below, When you have a brake fluid leak, consider checking these components first.

Defective piston seal: several brake components feature pistons in them, and this piston comes with seals. Brake components that feature pistons include drum brake wheel cylinder, disc brake caliper, and brake master cylinder.

The piston is a moving part that functions with hydraulic force. It has seals that prevent the fluid from leaking. Over time, these seals will tear due to normal wear or mechanical force, allowing the fluid to leak.

Damaged brake hose or brake lines: Brake hose and brake lines are made with strong materials to withstand rugged roads and extreme conditions. Over time, they can pit, rust or tear. Defective brake line fittings, broken brake lines, and torn brake hoses can result in fluid leaks.

Loosen or damaged bleeder valve: Each vehicle wheel has a bleeder valve, also known as a bleeder screw, used in bleeding air out of the brake systems. If the bleeder valve gets knocked loose or damaged due to rust, it can result in fluid leaks.

Worn out brake shoes, pads, drums, and rotors: Brake shoes, pads, drums, and brake rotors are subject to wear.

If these components wear out, it can cause the pistons to come out beyond how it is supposed to. This will damage the seal and cause fluid leaks.

Defective brake master cylinder reservoir: Most brake fluid reservoirs in newer cars are produced with plastic material and can become brittle due to excess heat in the engine bay. If this happens, it will apparently cause the reservoir to crack, causing the brake fluid to start dripping out and flowing down through the rear of the engine.

So, if you notice brake fluid leaking under the middle of the car, check the brake master reservoir for cracks or fluid around the area. The brake lines can also be a culprit.

Lousy ABS Module: The module consists of high-pressure brake fluid lines. Unfortunately, this component can rust or wear down due to mechanical force and cause fluid leaks.

Where does brake fluid usually leak from?

If you’re experiencing any signs of brake fluid leaks, the first thing is to check your brake system to confirm if there’s a leak somewhere around the car. Start by opening the hood. Check the brake fluid level to verify if the system is leaking.

A severe leak will drastically reduce the fluid level. If you can’t locate the brake fluid reservoir, consult your owner’s booklet. If the inspection confirms the fluid level is okay, there are chances that you have a small leak that could be allowing air into the system.

Check the following areas for fluid leaks;

  • Brake lines and hoses
  • Brake master cylinder
  • Front and rear calipers
  • Drum brake wheel cylinder (brake pot)

If you have found leaks in any of these areas, I will walk you through how to fix the leak, step by step, practically. Do not skim through; follow the below steps religiously.

How do you fix a brake fluid leak?

The first step in brake fluid leak fix is finding out where the leak is coming from. Once you have tracked down the real place the leak is coming from and its severity, the next step is to get things fixed and continue with your daily commute.

Now, I will assume you have figured out where the fluid is coming from. Let’s face it and fix it.

This walkthrough covers only rebuilding of brake caliper, changing brake hoses and lines, replacing the brake master cylinder, and generally bleeding.

brake fluid change

Method 1 out of 5: Rebuilding brake calipers

Nowadays, mechanics don’t rebuild brake calipers. Instead, they take it to a rebuilding station for a complete rebuild, and once the work is done, they reinstall the caliper. I recommend getting a new caliper rather than rebuilding the old one. The difference between a rebuilt and a new one isn’t much. If you choose to go for a rebuild and save those pennies, follow these steps.

Step 1: Detach the old caliper

  • Get a rebuild kit from your dealership or nearby auto store
  • Loosen the bleeder screw bolt. If it’s proving stubborn, apply penetrating oil to avoid breaking it or having it worn.
  • Detach the brake lines. Inspect the pipes and replace them if they are worn or cracked before reinstalling the caliper
  • Detach the slider pins, springs, shims, and pads from the caliper
  • Take off the caliper dust cover
  • Insert a piece of wood that is slightly bigger than the brake pads in the caliper against the piston
  • Send in compressed air into the caliper’s inlet port to push out the piston

Step 2: Reinstall the pistons

  • Oil the new piston you want to install with transmission fluid or any light oil
  • Insert and push the piston into the caliper. Do not forget the dust cover

Step 3: Reinstall the Caliper

  • Fix back the dust cover
  • Reinstall the slider pins, shims, pads, and springs with the new ones on the rebuild kit
  • Reinstall the brake lines
  • Reinstall the bleeder bolt
  • Cross-check your work and test it to ensure you have stopped the leak
  • Remove the air in the system by bleeding it.

Method 2 of 5: Rebuilding brake hoses and lines

If the brake fluid is leaking from the hose or lines, there’s no quick fix. Go ahead and fix it. And if the brake fluid is leaking from the rear wheel, inspect it closely. There are chances the leak is from the brake lines, not the wheel cylinder.

  • Raise the vehicle and support it with a Jack stand. Remove the tire
  • Disconnect the brake line from the master cylinder or any fittings nearest to it
  • Locate and remove all mounting clips/brackets holding the brake line
  • Detach the defective line from the caliper
  • Install the new line on the caliper. So not torque it yet.
  • Reconnect the mounting brackets/clips on the new brake line
  • Reconnect the other end of the brake line to where you removed it earlier
  • Cross-check your work and tighten everything single component
  • Remove the trapped-in air from the system by bleeding it.

Method 3: Replacing a wheel cylinder 

A defective brake wheel cylinder is much easier to replace, and it’ll give you peace of mind than rebuilding it.  A new wheel cylinder is almost the same as a rebuilt cylinder.

Step 1: Take off the wheel

  • Take off the wheel hubcaps.
  • Lift the affected wheel off the ground and support it with a jack stand
  • Unfasten the lug nuts and remove the tires
  • Apply penetrating oil on the brake line fittings so you can easily break them free.

Step 2: Take off the wheel drum

  • Remove the dust cover on the backing plate.
  • Reduce the drum brake adjustment with a flat-head screwdriver
  • Hit the center of the wheel drum with a hammer to break it loose from the rust
  • Pull off the wheel drum
  • Disassemble the brake components Consider getting new brake shoes if they are soaked with brake fluid
  • Clean the dirt and fluid on the drum surface with brake cleaner.

Step 3: Uninstall the brake line

  • Trace the brake line to where it joins with the wheel drum brake fittings and loosen it with a line wrench
  • Take off the brake fitting.
  • Prepare and place a vacuum hose on the brake firing to stop the fluid from leaking.

Step 4: Replace the brake pot

  • Find the bolts holding the wheel cylinder in place and uninstall them
  • Take off the defective wheel cylinder
  • Remove the vacuum hose on the brake line and thread it into the new brake pot by hand
  • Fix the new pot as you removed the old one
  • Expel trapped air from the system by bleeding it.

Method 4 of 5: Replacing the brake master cylinder

Newer brake systems have two circuits. Each of the circuits hosts two wheels, so if one of the circuits breaks down, the other one will sustain the brake system. The brake master provides hydraulic pressure to both circuits. So, if the brake master fails, it’ll affect all other brake components.

Getting a new one is much more accessible and affordable. If there’s a brake fluid leak on the master cylinder, it’ll affect both circuits and leave you with a flat brake pedal. Replacing it involves the following steps;

  • Raise the hood and find the brake master
  • Take off the fluid reservoir cover
  • Drain the fluid with a turkey baster. Recycle the drained fluid in a safe can.
  • Unplug the electrical harness
  • Loosen the brake lines with a line wrench
  • Unbolt the nuts holding the brake master in place
  • Take off the old brake master
  • Install the new unit
  • Fix the brake lines using the reverse process
  • Plugin the electrical harness
  • Remove the trapped in the air by blessing the system

Method 5: Bleed the brake lines

Always bleed your brake system after any system repairs that have to do with the brake lines. Brake bleeding requires assistance.

  • Ask your assistant to pump the brake pedal
  • Ask him/her to hold the pedal down while you lose the bleeder valve on the wheel cylinder or brake caliper. You have to bleed the wheels one at a time and not let air into the system.
  • Catch the brake fluid with a container, do not let it touch your paint. Brake fluid is corrosive to paints and wax.
  • Lock the bleeder valve and ask your assistant to pump the brake pedal a couple of times. Repeat the bleeding two or more times.
  • Repeat the process on all wheels.
  • Refill the brake fluid reservoir
  • Test the brake system to ensure it is working nice and smoothly.
Note: If you still have a spongy brake pedal after the repair, consider bleeding all the wheels to expel air from the systems.

If you change any component on one side of a wheel, always change the same component on the opposite wheel.


Q: How much does it cost to fix a brake fluid leak?

Several factors affect the cost of repairing a brake fluid leak, depending on your car make and model, the actual cost of the leak, and your location. Fixing a brake fluid leak can be relatively cheap. It is not going to break your budget. Here’s an estimated brake fluid leak repair cost.

  Repairs (One wheel) Parts     $10 – 20
    Labor     $80 – 100
  Replace Parts       $25 – 40
    Labor    $40-70
  Repair (one wheel) Parts     $70 – 150
    Labor    $50-100
  Replace (one wheel) Parts    $100 – 200
    Labor    $30 – 50
  Repair Parts    $80 – 200
    Labor    $50 – 120
  Replace Parts    $150 – 300
    Labor    $30 – 70
  Repair Parts   $10 – 40
    Labor    $30 – 50

If you’re a petrolhead and understand how the brake system works, you can fix the brake leak yourself. For every other person, the best thing to do is to consult your mechanic or dealership. Brake repairs is not a system fix you should play with. Your life and that of the passengers lie on it.

Q: Can you drive with a brake fluid leak?

Most brake systems in vehicles today work with hydraulics principles – they are activated with hydraulic force. So, it needs adequate brake fluid to provide peak performance. While you can drive a car without brake fluid, it is imperative to note that;

  • You are causing damage to other system components.
  • Your brakes will not hold. That is, high chance of getting crash
  • If you are caught driving without brake fluid on purpose, you’ll be issued a ticket.

Brake fluid is the most affordable thing in the brake system – yet, essential. Low or brake fluid leaks are the common cause of brake damage and collisions. Hence, do not drive your car without brake fluid.

 Q: How serious is a brake fluid leak?

As explained earlier, brakes work with hydraulic force. Brake fluids help in carrying out the driver’s demands as he steps on the brake pedal. If a brake fluid leak occurs, the brake system will lose the hydraulic forces needed to function optimally, leading to the inability to stop your car.

Q: Can brake fluid go low without a leak?

Absolutely yes. When the brake pads and shoes wear out, the system will send the hydraulic fluid into the caliper or wheel cylinder. As a result, the brake fluid on the reservoir will reduce. That said, do not confuse this situation as a fluid leak. The moment you replace the worn-out brake pads and shoes, the fluid will return to the reservoir.

Q: Is it safe to drive a car without brake fluid?

While the brake fluid won’t stop your car from moving, you should note that your brakes will not hold without brake fluid. In simple terms; no fluid, no brake. Driving without brake fluid is totally unsafe because your brakes will not hold. Do you know what that means? You’re preparing for a crash! 

Final word

At this point, you have seen the causes, symptoms, and how to diagnose and fix brake fluid leaks. Aside from the general causes, there’s a particular cause that affects only a specific environment.

For example, if you live on the coast with a lot of salt in the air or drive in salty areas, you may have rusted and damaged brake lines more often.

Lastly, because some brake jobs are more accessible to fix than others, and parts replacement cost varies, it will be difficult to estimate the actual cost of repairing a brake leak.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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