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Your vehicle’s brakes malfunctioning while you’re driving is one of the worst-case scenarios you never want to live through, and any loss of brake fluid in your brake system can cause brake failure. Even small leaks will require you to top up your brake fluid more often than usual, which is why leaks in your brake system should be taken very seriously.

How Long Can I Drive With Leaking Brakes?

If you notice a leak, have your brakes inspected and repaired as soon as possible. When brake fluid leaks, it leads to a loss of pressure in the brake line, leading to eventual brake failure. In addition, when you have a leak in your brake system, air can enter the system and cause stopping issues.

When you have a leak in your brake system, air can enter the system and cause stopping issues.

Anthony Harlin, ASE Certified Master Automobile Technician

As a safety precaution, all vehicles from the late ‘60s and onwards have their hydraulic brake circuits split into two. This helps prevent a total loss of brakes if one circuit’s line fails, as the other set will still work. In case of sudden and unexpected failure, this might be enough to get you safely to the side of the road. If one set of lines breaks though, the other set will likely follow suit soon.

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In addition, only two brakes working instead of four won’t be as effective at stopping your vehicle. The distance your vehicle will travel before coming to a stop will increase as a result. This is incredibly dangerous, especially in emergency situations.

brake fluid leak beneath a brake disc and caliper
When brake fluid leaks, it leads to a loss of pressure in the brake line, leading to eventual brake failure.

Why Is My Brake Fluid Leaking?

Now that we know what can happen thanks to brake fluid leakage, let’s take a look at what causes brake fluid leaks in the first place.

Broken or Rusted Brake Lines

Brake fluid leaks can be caused by cracks or breaks in the rubber brake hoses or rusted holes in the steel brake lines.

Rusted brake lines are one of the most common causes of brake fluid leaks. The double-wall, furnace-welded lines use steel so they can withstand hundreds of pounds of pressure from a hydraulic brake system. Unfortunately, even stainless steel can corrode over time, especially if you live in a cold weather state. Exposure to years of road salt over the winters can worsen this even more since salt has corrosive properties on the metallic brake lines in your vehicle.

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If the anti-corrosion coating on your steel lines isn’t high quality, the rust problem can only get worse. Once the rust eats through the steel, the line will fail, causing brake fluid to leak out. That’s why keeping an eye on any symptoms of a leak in these lines is essential.

Broken Wheel Cylinder Seal

If your vehicle has drum brakes, a broken wheel cylinder might be to blame for the brake fluid leaking from the rear wheel of your vehicle. When the wheel cylinder springs a leak, the connected brake circuits are affected, resulting in a loss of pressure in the brakes. These leaks are linked to the seal of the wheel cylinder, which is meant to keep the fluid pressurized. The seals protect the cylinder from moisture and debris, but they will fail over time.

Bad Brake Caliper

If your vehicle has disc brakes, another possible reason for the brake fluid leaking around your wheels is a bad brake caliper. Each wheel has a caliper that helps squeeze the sides of the rotor to apply the brakes. The piston seals around these parts wear down as your vehicle ages, which may lead to brake fluid leaking out.

image of an old brake caliper and brake disc
A bad brake caliper can lead to brake fluid leaks.

Low Brake Pads

Wear and tear on your vehicle’s brake pads might also lead to a brake fluid leak. When your brake pads get too low, then your piston over extends, causing it to leak as well.

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Faulty Brake Master Cylinder

A brake fluid leak in the brake master cylinder can be more difficult to notice. In this case, the fluid often goes straight into the vacuum brake booster and into the engine, meaning there’s no external leak to notice. This type of leak can come from incorrectly pumping the brake pedal to bleed the brakes.

Here’s a tutorial video on how to bleed the brakes:

Water Contamination

Brake fluid is hygroscopic and can absorb moisture in the air, even through the lines. As a result, water contamination can occur. When there’s enough water in the system, it will start rusting the lines from the inside out, causing leaks.

Always take any potential problems  with your vehicle’s brakes seriously. The last thing you want is for them to fail when you need them the most. You need to stay vigilant and make sure all parts of your brake system are in good working condition at all times.

About The Authors
Anthony Harlin, ASE Certified Master Automobile Technician
Reviewed By Anthony Harlin, ASE Certified Master Automobile Technician

Technical Reviewer at

Tony Harlin is a Master Gas and Diesel Diagnostic Technician with over 18 years of experience. He works full-time at a large independent automotive shop as a driveability and repair technician working on all types of vehicles with a focus on diesels. ASE certifications include A1-A9, L1 and L2, as well as X1.

CarParts Research Team
Written By Research Team

Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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