Many people assume any issues with their brakes is as simple as changing the pads and rotors. Did you know there is much more to maintaining your vehicle’s brakes? What is a brake system flush? Why is it important?
Your brakes consist of more than just brake pads. An overlooked item is brake fluid. In this article I will answer the question what is a brake system flush? Brakes need fluid to function and that fluid needs to be changed once a year to keep your brake system operating correctly. A brake system flush will ensure that your vehicle’s braking system works at it’s peak level.
This article aims to answer questions and show you why a brake system flush is an important service that should not be ignored.
What is a brake system flush and why is it important?
Before we jump into what a brake system flush actually is, let’s take a second to learn a little about brake fluid itself and a little about some common brake issues.
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Brake fluid is a glycol-ether based hydraulic fluid, there are mineral oil based fluids as well as silicone based (DOT 5) The most common fluid is DOT 4 or DOT 3 brake fluid.
There are a few things to know about brake fluid.
- It is hydroscopic
- It does not expand in high temperatures
- It must have consistent viscosity at all temperatures
- It must combat corrosion and protect rubber components in the brake system
I don’t want to get into the chemistry of brake fluid in this article, however the examples above are very important to understand, they are the main reasons brake fluid needs to be flushed.
Why does brake fluid need to be flushed?
Brake fluid is hydroscopic, this simply means it absorbs water. Over time the moisture in the brake system builds up, the brake fluid retains this moisture. I probably don’t need to tell you moisture in your brake system will cause issues. Over time the moisture starts to oxidize the fluid and turn it dark and nasty, plus the fluid will lose it’s ability to not expand under heavy heat.
This can cause brake drag and overall loss of brake pedal “feel.” In essence, your braking system is less efficient and effective at this point. As you can see we really put a lot on the shoulders of our brake fluid. The good news is quality brake fluid that is flushed every year will keep your brakes working properly.
How does brake fluid work?
Brake fluid works on the principal of hydraulics, liquid does not compress. Brake fluid transfers the energy your foot applies to the brake pedal to the brake calipers and rotors. This in turn converts the energy of your rolling vehicle to heat. This is the short version but it shows that the real work is being done by the brake fluid.
What is a brake system flush?
A brake system flush is the process of completely removing old brake fluid while adding new fluid behind it until the entire system has fresh fluid. Each wheel has a bleeder screw that when opened lets the fluid flow out of the component, it can be the caliper or wheel cylinder.
Think of it as drilling a hole in the bottom of a bucket filled with water and adding fresh water in as the old runs out, the bucket always stays full so no air is introduced, however eventually the water in the bucket is all fresh.
This is the main goal when flushing a brake system.
Three ways to flush your brakes properly.
#1 Pressure Flushing
Pressure flushing requires a tool that holds fresh brake fluid and air pressure on separate sides of a rubber diaphragm. Using a adapter that seals to the brake master cylinder the air pressure pushes the fresh fluid into the master cylinder as you open the bleeders at each wheel.
This is by far the fastest and most effective way to flush a brake system.
#2 Manually pumping the brake pedal
This is better for just bleeding the brakes but it will work to flush the system with some patience. You will need a friend in the driver’s seat. This procedure is done by is having a friend pump the brake pedal at least three times and the holding pressure on the pedal as you open the bleeder screws. This pushes old fluid out, over time the whole system can be flushed. This iss the long way but still gets it done.
Keeping enough fresh fluid in the reservoir and making sure your buddy does not let the pedal up until you close the bleeder is key here. It will take a few times at each wheel but the fluid will eventually flow clean.
#3 Vacuum Bleeder
Vacuum bleeding is the same principal except you are sucking the fluid out of each bleeder instead of pushing it out. There are special tools that use compressed air to get this done. These use a silicone line attached to the bleeder nipple that pulls the fluid out using a venturi effect. You need to keep the master cylinder full enough so you do not suck air into the system with any of these techniques.
Wrapping up what is a brake system flush.
I hope you have learned a little about what a brake system flush is in this article. At the end of the day whether you take the project on yourself or pay a pro to get it done, you have made a good investment in your vehicle, and more important you and your families safety.
I recommend getting your brake fluid flushed every year with a good quality fluid that matches your vehicle’s specifications. You will enjoy a better stopping and driving experience.