An In-Depth Guide On Bleeding Your Car's Brakes
Bleeding your car's brake lines is a must-do task if you plan on changing the brake fluid. Bleeding the brake lines not only purges them of worn brake fluid, but it also prevents air from getting trapped in the lines. While this task has a bit of a reputation for being difficult and somewhat intimidating, it can be done as long as you follow the instructions and tips found below.
Making Preparations
This guide assumes that you've already changed the brake fluid in the master cylinder reservoir. Your vehicle should be supported on jack stands, with all four wheels off the ground and all four tires removed. It's a good idea to locate the bleeder valve at each brake caliper or wheel cylinder before you get started. You may want to add a dab of penetrating oil just to make it a little easier to crack open the valve when the time comes.
Keep in mind that bleeding the brake lines is a two-person job. You'll need an assistant who can press the brake pedal on command as you work on bleeding the brakes. You'll also need to bleed the brakes in the correct sequence for your vehicle. The correct bleeding sequence can usually be found in your vehicle's factory manual or service manual. Bleeding the brakes out-of-sequence can suck air into the brake lines.
Getting Down to Business
After making the proper preparations, you can get started with bleeding your car's brakes:
- Double check the brake fluid level in the master cylinder reservoir. Make sure the fluid is at the fill mark and that the cap is tightly fitted on the reservoir.
- Go to the first wheel as specified in your factory manual's bleeding sequence. In most cases, this will be the rear wheel furthest from the master cylinder.
- Take a long length of tubing and place it over the bleeder valve. The tube should fit snugly over the valve. Stick the other end of the tube into a glass mason jar.
- When you're ready, slowly open the bleeder valve using a bleeder wrench. A crescent wrench of the appropriate size will also do in a pinch, although you'll have to be careful to avoid stripping the valve nut.
At this point, you'll want to have your assistant pump the brake pedal. While this is happening, keep a close eye on the fluid coming out of the bleeder valve. Once you start seeing fresh fluid coming out of the bleeder valve. Quickly close it and move on to the next wheel in the sequence.
When you're finished, give your vehicle a brief test drive to make sure the brake pedal works as intended. The pedal should have a firm and solid feel to it when pressed.
Dealing with ABS-Equipped Vehicles
In some cases, air can become trapped within the module that actuates the anti-lock brake system. Because of the complex valves within the module, you won't be able to vent trapped air out of the unit using ordinary methods. The bleeding procedure varies among the different manufacturers, but in most cases, you'll need a pressure bleeder and a scan tool to successfully complete it.
A Few Words of Caution
As you're bleeding the brakes, you'll want to make sure you don't run the brake fluid in the master cylinder reservoir dry. Doing so could introduce more air into the brake system, making your job that much more difficult. Periodically check the brake fluid levels and top off the reservoir with fresh fluid as needed.
Also, you don't want your partner to press the brake pedal all the way to the floor during the brake bleeding process. To keep this from happening, you can place a 1x4-inch block of wood underneath the brake pedal to act as a temporary stop.