flush brake fluid

A brake fluid flush is part of routine maintenance. Although the reasons you need it may not be obvious, having your brake fluid flushed out regularly is crucial. Doing so helps remove moisture buildup, protects your brake lines, and ensures the brake fluid quality provides sufficient stopping power.

If you neglect your brake fluid, your brake lines can become corroded, your brake pedal can feel soft, and other brake components can suffer. In the worst situations, your car can have trouble braking, resulting in a dangerous condition that can cause accidents.

Thankfully, the cost of having your brake fluid flushed is minimal. Many people can do it themselves by jacking up each wheel and opening the bleeder valve while someone else steps on the brake pedal. But you can also take it to a mechanic to have the brake lines flushed quickly, typically costing less than an hour of labor.

Why Ignoring a Brake Fluid Flush Could Cost You More Than You Think

The braking system in every vehicle is a closed hydraulic network, meaning nothing should leave or enter the system while it is in operation. Maintaining the closed system is crucial so the hydraulic fluid is appropriately relocated to provide stopping power.

When you press down on the brake pedal, the brake booster amplifies this force and forces the brake fluid through the brake lines toward the calipers. This pressure pushes the brake pads, increasing their friction with the rotors and causing your car to slow down.

Brake fluid is designed to meet specifications to compress and transfer the braking force precisely and minimally. To ensure your brakes function as intended, it is important to flush the brake system regularly.

1. Prevent Moisture in Brake Fluid

Prevent Moisture in Brake Fluid

Most brake fluids are hygroscopic, drawing in water molecules from the environment. Silicone-based DOT 5 is the only exception but is much less common than DOT 3 and DOT 4.

Water accumulation occurs slowly, leading to a higher proportion of water in the brake fluid over time. Water can also enter the system through other imperfections in the master cylinder, brake lines, or bleeder valves.

The braking process generates a lot of heat, so one of the most critical aspects of brake fluid is its high boiling temperature. When excess water enters the brake fluid, the boiling point decreases. This can cause air bubbles to form in the system, resulting in a spongy brake pedal and less efficient braking.

2. Protect Brake Lines

Protect Brake Lines

As a closed hydraulic system, the brake lines need to be in excellent condition to allow the fluid to transfer force from the brake pedal to the pads and rotors. If there are any imperfections in the brake lines, your stopping power suffers.

Problems with brake lines can be caused by excessive water accumulation in the brake fluid. This causes air bubbles to form when the boiling point is lowered, allowing problematic corrosion to form. Rust can eat through vital brake lines and other brake components.

Brake lines can also get damaged during the operation of your vehicle, which could cause the closed system to have a leaky opening that can sometimes go unnoticed. When you flush the brake system, it allows you to closely inspect the brake lines for any signs of air bubbles, corrosion, or damage.

3. Ensure Brake Fluid Quality

Ensure Brake Fluid Quality

Stopping a vehicle weighing thousands of pounds takes significant effort. Since the braking system is routinely put through punishing conditions, it is critical to flush the brake fluid regularly.

While brake fluid is resilient to this challenging environment, it does not last forever. To verify your brakes provide sufficient stopping power and that brake components are not damaged, the brake fluid needs to be regularly replaced by flushing it through the system.

5 Telltale Signs Your Car Needs a Brake Fluid Flush

Unlike other routine maintenance items like oil changes and tire rotations, the rules for brake fluid flushes aren’t quite as clear-cut. A great place to see how often you should flush your brake fluid is in your owner’s manual maintenance schedule.

But there are many other times when you should perform a brake fluid flush.

1. During Routine Brake Maintenance

During Routine Brake Maintenance

Flushing your brake lines should be part of routine maintenance on its own and when you perform other brake repairs or replacements. Many people will always flush brake fluid whenever the brake pads, rotors, or calipers are repaired or replaced.

Sometimes, your brakes can last years without needing attention. If that’s the case, you should still stick to a routine for brake fluid flushing. Some people flush brake fluid every four to five years, but to keep your brakes in better shape, we recommend flushing your brake fluid every 30,000 miles or two years, at minimum.

You can save time and money by having a brake fluid flush performed when you have your tires rotated. Since the wheels will already be off, it should be a faster and cheaper service.

2. Brake Pedal Feels Soft

Brake Pedal Feels Soft

If you ever notice a change in how your car brakes, it’s important to address the issue immediately. When the brake pedal feels soft and pushes down easier or further than usual, it clearly indicates that your brake fluid needs to be flushed.

A soft brake pedal often means water or air has entered the brake lines. When you press on the pedal, the brake fluid compresses more than it should, allowing the brake pedal to go down more easily rather than transferring the force directly to the brakes. Flushing the lines will typically fix this.

3. Leaking Brake Fluid

Leaking Brake Fluid

Brake fluid should not leave the system. If you notice that your brakes are leaking fluid, you’ll need to identify where the leak is coming from. Sometimes, it’s a simple repair, such as a bleeder valve that was left a little loose.

Other times, brake lines can have fluid contaminated with water freeze, expand, and rupture the brake line. Corrosion and rust can also eat through brake components. Damage to the brake parts, especially the vulnerable brake lines, can happen while driving.

Once you repair the leaking component, you should flush the brake fluid to remove any contaminants that enter the system. Keep a close eye on the ground below your car and the brake fluid level in the master cylinder to ensure the leak does not reappear.

4. Brake Fluid Is Contaminated or Low

Brake Fluid Is Contaminated or Low

Another time you should have your brake fluid flushed is when the fluid is contaminated or gets low. You can check your brake fluid by opening the master cylinder, the reservoir with excess brake fluid under the hood.

Most brake fluids are nearly clear with a slight yellow tint. If you notice your brake fluid is darker, has a cloudy appearance, or looks contaminated, it’s time to flush and replace it.

The fluid should not change in its level over time. So, if you notice the fluid is low, the system is likely leaking. These can be hard to spot as they might only happen when you break.

5. ABS Warning Light Turns On

ABS Warning Light Turns On

Another time that can indicate you need to flush the brake fluid is if the ABS warning light comes on. This can be caused by various issues, such as a bad ABS sensor or failed wheel bearing, but sometimes, it happens when the brake fluid needs to be flushed.

You can connect an OBD-II reader to pull the codes and gather more information about the problem. Or, if you want to try a quick, inexpensive fix, flush the lines and see if the light goes away.

Step-by-Step Guide: How to Change and Flush Brake Fluid Like a Pro

How to do a Complete Brake Flush and Bleed

Flushing the brake fluid is a relatively simple process that most people can do on their own by following these steps:

  1. Remove excess fluid from the master cylinder with a turkey baster, syringe, or another suction device. Get as much out as you possibly can.
  2. Fill the master cylinder with the appropriate brake fluid based on your manufacturer’s recommendation. Most vehicles that call for DOT 3 can also use DOT 4, but if your car needs DOT 5 or 5.1, do not use anything else.
  3. Check your service manual to see how you should flush the brake lines. Usually, you start with the wheel farthest from the master cylinder, then get closer to it through each of the four wheels.
  4. Jack up the first wheel, place the jack stands underneath your car, and remove the wheel.
  5. Locate the bleeder valve on the caliper and place a line of hose over the top of it and the other end into an empty container.
  6. Have someone sit in the driver’s seat, open the bleeder valve, and push down on the brake pedal. You should see the fluid come through the line.
  7. Just before they hit the floor with the brake pedal, close the bleeder valve. Then, they can release the brake pedal.
  8. Repeat this process until the new fluid comes out of the bleeder valve and the brake pedal feels stiff when the bleeder valve is closed, showing the brake fluid is refreshed and there is no water or air in the lines.
  9. Put that wheel back on, lower the vehicle, and repeat the process through the other three wheels and brake lines. Make sure to top off the master cylinder with brake fluid as you go through. You don’t want to suck air into the system, or else you’ll need to start from the beginning.
  10. Finish by ensuring the master cylinder has brake fluid up to the maximum line, test that the brake pedal feels firm, and then go for a slow test drive to ensure you have adequate braking power.

If your brake fluid is in extremely bad condition, you use a specific chemical to clean out the lines. This is known as a chemical brake fluid flush. You’ll flush the lines once with the cleaning agent, then finish by flushing with the normal brake fluid for operation.

If you don’t have another person to pump the brake pedal, specialty systems are designed for one-person brake fluid flushing. They typically attach to the bleeder valve and use a vacuum to suck the fluid down from the master cylinder and out through the bleeder valve.

How Much Does a Brake Fluid Flush Cost?

Cost of a Brake Fluid Flush

The tools and knowledge required to flush the brake fluid yourself are minimal. You basically only need the new brake fluid, a turkey baster, a wrench that fits the bleeder valve, and, to avoid spills, a short hose that fits the bleeder valve.

If you do it yourself, the only recurring cost is the brake fluid, which is typically anywhere from about $7 to $40 per quart, with the more expensive end reserved for high-performance vehicles or classic cars stored for long periods.

But if you’d rather have a professional handle the job, it’s still quite affordable. It should be no more than one hour of labor at most. Most vehicles can have the entire brake fluid flushed by a mechanic for around $75 to $125.

From Sluggish Stops to Screeching Halts

It’s important to flush your brake fluid regularly to remove any water, air bubbles, or contaminants from the fluid and lines. You’ll want to do this about every two years, at minimum, or when you notice a soft brake pedal, a fluid leak, or during routine brake repair.

To flush the brake fluid, suck the excess fluid out of the master cylinder, remove the wheel farthest from it, open the bleeder valve as someone presses on the brake pedal, and close the valve as they release the pedal. Continue this until fresh fluid comes out, then repeat for each wheel.

Jason Farrell

Written By

Jason Farrell

Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.

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