A vehicle’s brakes are responsible for keeping its occupants safe while protecting the people and property in the surrounding area. Imagine how long it would take to coast to a stop after achieving speeds of 75 mph?
When a driver pumps the brake pedal, fluid courses through internal systems to ensure that the pads or discs engage as expected.
Most people know that when their brakes start grinding or squealing that it is time to have those parts replaced. What often gets overlooked during that service is the quality of the brake fluid.
The average vehicle should have its brake fluid flushed about once every two years.
How Much Brake Fluid Do I Need for a Flush?
The average vehicle requires between 0.5 to 1 liter of brake fluid to operate correctly. When flushing the system, additional liquids are necessary to expel the old product out of the lines. Most systems work better when the same amount of brake fluid is used for flushing the system, doubling the recommended amount.
If you have a vehicle that requires 500 ml of brake fluid to operate correctly, you should plan on flushing the system with 500 ml before replacing it with another 500 ml of clean liquid.
That means you’ll double the amount required to have a successful flush.
If you have a vehicle that requires one liter of brake fluid, you will flush that system with a liter before installing the new product.
Most brake fluid containers tell you how much product is available, but you’ll need to remember that some liquids will stick to the sides. If you use an entire 500 ml container to change your brake fluid, it won’t be quite that amount.
You’ll want to top it off with a touch from another container or use a tool to bring the clinging liquid out of the container.
Why Do I Need to Flush My Brake Lines?
Brake fluid is a type of hydraulic fluid. It’s used in hydraulic clutch applications and brakes to transfer the force from the pedal to the rest of the system.
That’s how you can stop faster when stomping on the pedal, but then have a longer slowing period with a slight depression.
The brake system on a vehicle is not indestructible. It contains rubber valves that eventually deteriorate, leaving sediments that end up in the brake fluid.
A vehicle’s brake fluid can also get worn out and stop transferring energy as expected. This issue happens when water gets into the lines, rust forms, or other contaminants develop. These issues are why used brake fluid often looks muddy or soapy.
Until the brake lines get flushed with clean fluid and then replaced with a viable product, a vehicle’s stopping power will always be less than optimal.
Signs and Symptoms of a Brake Fluid Problem
When a vehicle’s brake fluid isn’t functioning as expected, the warning lights or messages reflecting this information may display for drivers to see. If you experience this issue, it is important to schedule a flush and service inspection right away.
It is also possible for a brake fluid problem to exist without triggering any warning messages or dashboard displays.
Even if your sensors aren’t detecting a problem, you’ll see some common signs and symptoms that suggest a brake fluid problem exists. If you experience one or more of the following issues, you’ll want to take a deeper dive into the situation to see what is happening.
Brake Pedal Malfunction
A vehicle’s braking system should respond to every bit of pressure placed on it when pressing the pedal. If you don’t receive an expected response, there could be an issue with your fluid quality or quantity.
Most people describe the experience as having a “soft” pedal. If you must press the pedal harder to get the same stopping power, it’s worth having an inspection and a flush to ensure proper operations.
New or Strange Noises
When a vehicle starts getting low on braking fluid, more friction enters the entire system. This reaction eventually creates a grinding, ratting, or scraping sound that you can hear whenever you press the pedal.
The sounds you hear are components rubbing against other parts to encourage the vehicle to stop. Without proper lubrication and pressure, premature wear and tear occurs that could eventually require a significant repair.
Uneven Brake Pads
Once a vehicle’s brake fluid starts running low or has quality reductions, the pedals cannot depress the pads with the same force on both sides.
That outcome creates uneven wear that eventually causes grinding or squealing sounds because the metal from the pad contacts the rotor.
Uneven brake pads can also cause the car to rumble or vibrate whenever you push down on the pedal. This symptom creates a dangerous situation if you must complete a high-speed stop because the steering wheel jumps to the left and right.
Burning Smells
When brake fluid starts overheating, it produces a strong odor. You will smell it when there isn’t enough liquid in the system to circulate the heat correctly when the pads are depressed. If the system gets too hot, it can fail.
You’ll need to pull over and stop the vehicle to let the brakes cool when this issue occurs. Drive carefully until you can reach a service station or get home to flush the system and add more brake fluid.
Best Brake Fluid to Use for Flushes and Fills
The best brake fluid to use for most vehicles is Bosch ESI16-32N. It serves as a direct replacement for DOT 3, 4, and 5.1 in current vehicles and lasts up to 100% longer. The product has a wet boiling point of 365°F while staying viscous down to -40°F.
Even though the recommended change interval for brake fluid is two years, this Bosch product comes with a three-year recommendation.
That means you get the benefits of each DOT number while having a high-quality replacement for your flush and fill.
| DOT 3 | This brake fluid formula typically comes with an ether-glycol base. The minimum wet boiling point is below that of water temperature, so it serves vehicles that have general purpose needs to fulfill, such as a daily commute to work. |
| DOT 4 | The fluid in this category has additives to raise the minimum boiling to serve more needs. It’s meant for racing or performance vehicles, which means frequent changes are necessary. Some drivers might need to schedule a flush and fill annually. |
| DOT 5 | This brake fluid doesn’t work with any other, but it delivers superior results. It won’t attract water, damage paint, or encourage corrosion within the system. You receive the benefits of the other types, but vehicles must be designed to operate with it. |
| DOT 5.1 | You’ll receive a lower viscosity product with this option while having a chemical composition similar to DOT 3 and 4. You receive the same boiling points as a standard 5.1. |
How to Flush Your Brake Fluid at Home
Most local service providers will flush your brake lines as part of their regular services and maintenance offers. If you go in for an oil change, this service is a typical add-on.
When you want to save a little money, you can also flush your brake fluid at home. You’ll need about twice the recommended amount for a full fill to ensure the old liquids are purged from the lines.
First, you’ll need to empty the master cylinder reservoir. All the fluid must get taken out of this container. It can be done with a transfer pump and tube, a small siphon pump, or even a turkey baster. The vehicle should be in park, turned off, with no pressure on the brakes while taking this step.
After removing the brake fluid from the master cylinder reservoir, you’ll fill it with fresh fluid. Fit a small section of clear tubing over the bleeder screw to make it easier to see when all the old fluid is gone. Begin at the rear of the vehicle first, bleeding out the rear wheel cylinders and calipers.
Once the old brake fluid is gone, you’ll see fresh, clear liquid flow through the tube. That’s when you know it’s time to repeat the process at the front.
When the last wheel is finished, you’ll need to return to the master cylinder reservoir. Fill it back to the indicated line, and you’ve finished flushing your system.
Most brake fluid products are rated to last for two years. If you drive more than 15,000 miles per year, consider changing the flush and fill schedule to every 30,000 miles instead.
How Important Is It to Flush My Brake Lines?
Vehicles equipped with anti-lock brake systems and traction control require frequent fluid maintenance to ensure proper operations. Most brake fluid is hygroscopic, which means it can attract moisture from the air. That causes it to develop water in the lines that eventually leads to corrosion.
My first vehicle was a 1979 Mercury Capri. That model year introduced the second generation of the Capri, ending the branding with Ford to create a counterpart to the Mustang that was a little more affordable.
The salesperson told me that a local grandmother kept the car in her garage the entire time, which is why the odometer only said 25,000 miles.
I laughed because the interior showed the wear and tear of 125,000 miles, but it didn’t matter. The vehicle would be beautiful with a little restoration work.
I took care of the red leather interior first. After that, the outer white paint got a refresh. The third item on my list was to bleed the brakes and flush the fluids.
My first mistake was doing the work on my gravel driveway. The second mistake was forgetting to cap off the system after the flush, so all the new fluid just went right on out. It was a good, if not frustrating, learning experience.
That car got me through the first four years of driving. It ran like a charm, had a quirky stereo system, and hated having my friend Joe in the back seat because the acceleration profile was terrible with the extra weight. Even with the extra work put into it, I wouldn’t have traded that car for anything in the world.
When the engine finally died on it, I was devastated. I sold it to a friend who wanted to put in a new 302 with turbos and, last I heard, he was still driving it around town.
Brake fluid changes should not be overlooked. When you stick to a proper maintenance schedule, your vehicle will take care of you.