How To Repair A Brake Line (6-Step Guide)

Wondering how to repair a brake line? Not to worry, you're in the right place!

In this guide, we'll show you how to:

  • The two reasons brake lines usually fail 
  • How to install a new brake line, or
  • How to do a partial DIY brake line repair

And more!

Man Repairing a Brake Line

If you've ever gone to push the brake pedal down only to find that it drops to the floor with little resistance, you are well aware of the symptoms of a sizable brake fluid leak and the fearful experience that this can cause. 

Brake fluid leaks are an all too common problem that is encountered by a significant number of motorists each year.

So, before you dive in to your DIY project, I recommend you read on to learn how to repair your brake line well!

What Causes Brake Line Failure?

Two of the most common causes of a brake fluid leak are failures in wheel-end components such as brake calipers and wheel cylinders, as well as corroded or rusted-out brake lines. 

While the first of these two issues require a simple component replacement, the latter can be more complex to fix, and often leaves an individual questioning how to repair a brake line.

While impacts from road debris do occasionally lead to damaged brake lines, these lines are typically well protected, as most are tucked away along a vehicle’s frame rail. The far greater foe to a brake line’s structural integrity is corrosion. 

This is especially true in northern areas that experience substantial winter weather and notable snowfall. This prevalence of wintry precipitation makes salt and calcium chloride applications quite common as a de-icing measure.

Both of these substances are highly corrosive and damage metal surfaces relatively quickly. Read this article for more about the effects of winter-related brake failure.

After years of being exposed to corrosive substances, the metal structure of a vehicle’s brake lines begins to rust, flake, and deteriorate. This eventually compromises a line’s ability to withstand the hydraulic force imparted by the braking application itself. 

This results in a leak that can cause less than adequate stopping potential and creates a safety hazard. When this occurs, immediate repair becomes a necessity. To read more about causes of brake line failure, click on this link.

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Did You Know: Fun facts about brake lines.

What Are Your Options For Repairing A Brake Line?

When a leaking brake line becomes evident, there are only two options for remedying the situation, repairing the line by replacing the damaged section, or replacing the line in its entirety.

The decision of which path to proceed with comes down to the extent to which the remaining portion of the line is corroded. 

To replace just the section of line that is leaking, the remaining portion of line must be in good shape and relatively free of rust.

You do not want to attempt a sectional repair if the surrounding portions of line are found to be in poor shape as well. If the remaining line is compromised, the entire brake line should be replaced.

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Supplies Needed To Repair A Brake Line

Pick these DIY supplies up at any auto parts store:

  • Jack stands
  • Flathead screw driver
  • Line wrench
  • New brake line
  • Brake fluid
  • Permanent marker
  • Tubing cutter
  • Tape measure
  • Flaring tool 

How To Replace A Brake Line (6-Step Guide)

  1. Disconnect Hold-Down Hardware
  2. Disconnect Nuts At Line Ends
  3. Remove Line From Vehicle
  4. Place and Fit New Brake Line
  5. Bleed Brakes
  6. Check For Leaks

Step 1 - Disconnect Hold-Down Hardware

It is standard for brake lines to be secured to a vehicle’s frame rail with plastic bracketing. You must free the brake lines from this bracketing before removal.

This can be easily accomplished with the aid of a flathead screwdriver that is used to pop the sectional portions of the hold-downs apart.

Step 2 - Disconnect Nuts At Line Ends

You will now loosen and disconnect the nuts or fittings at each end of the line. This should be done with the use of a line wrench to prevent the rounding out of these fittings.

Step 3 - Remove Line From Vehicle

With each end of the line loose, it will be time to remove it from the vehicle. This can, at times be tedious, especially if the line in question is of lengthy proportions, such as one that runs from the engine bay to the rear brakes.

With patience and finesse, slide the line out of place.

Step 4 - Place and Fit New Brake Line

With the new line in hand, you will now begin the installation process in the reverse order of how the old line was initially removed.

Ensure that the line is routed correctly, the line’s fittings are tightened to each end’s corresponding fitting, and lines are repositioned in all hold-down brackets.

Step 5 - Bleed Brakes

You will now top off the vehicle’s master cylinder with brake fluid and bleed the brakes to ensure that the system is void of any air.

After this process has been completed at every brake bleeder, ensure that your brake fluid level is once again topped off.

Step 6 - Check for Leaks

Once you have bled your vehicle’s brakes, visually inspect your repair for any sign of leaks. If any such leaks are found, do not drive the vehicle.

Instead, seek out the cause of this leak.

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How To Complete Sectional Replacement Of A Brake Line in 7 Steps

If you have located the source of your vehicle’s brake fluid leak, and the line to each side of this damaged section appears to be in respectable shape, you can simply remove and replace the section in question.

The following steps outline this procedure.

Step 1 - Measure And Mark

Begin by determining where the problem section of line begins and ends. You will need to ensure that all rusted and corroded lines are removed to produce a quality flare and a proper seal.

This is best accomplished by measuring six inches past the last area of visible damage to each side. These points can then be marked with a permanent marker.

Step 2 - Make Precision Cuts

You can now begin cutting out your damaged section of old brake line with the use of a tubing cutter.

This cutter will be circled around the circumference of each mark made in step one, in an even and concise manner, to make sure that each end is squared off.

Step 3 - Locate Replacement Line And Fittings

Take measurements of the diameter of the brake line that you have just cut. This will ensure that you purchase the proper line to complete the repair.

Locate and purchase a section of line in the appropriate length and diameter, as well as both male and female fittings for each end of the line that is of the correct size.

Step 4 - Deburr and Flare Line

You will now ensure that each end of both the replacement, as well as stock, line segments are free of any burrs that could hamper the flaring process.

Next, with the use of a flaring tool, you will use the provided jig and dies to produce a double flare on each end of both the new and old sections of line. 

Be sure to place the corresponding male and female fittings on your line before flaring, as you will not be able to do so once flaring is complete.

Step 5 - Connect Segments

With the use of a set of line wrenches, tighten the corresponding fittings on each end of the line until they are snug.

This can take some gentle force, as you will be seating your new double flare connections in with one another to form a seal.

Step 6 - Bleed Brakes

You will now top off the vehicle’s master cylinder with brake fluid and bleed the brakes to ensure that the system is void of any air.

Step 7 - Check For Leaks

Once you have bled your vehicle’s brakes, visually inspect your repair for any sign of leaks. If any such leaks are found, do not drive the vehicle. Instead, seek out the cause of this leak.

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Getting Back On The Road

While experiencing a full or partial brake failure can be nerve-racking, repairing a damaged brake line does not have to be.

Assess the situation, choose whether to repair or replace the line in question, and carry through methodically with your intended fix.​

If done correctly, you will have your vehicle’s brakes back in operational shape in no time, and be back on the road yet again.

About Your Mechanic

About Josh Boyd

I’ve been an ASE Certified automotive/heavy equipment technician since 2010. I began my career performing basic automotive maintenance at a service center before working as a Toyota technician at my local dealership.

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