As critical components go, your braking system is top of the list. However fast you’re going, you need to be able to stop on demand. Vehicle braking systems are hydraulic, which means they work by pushing pressurized fluid. If there’s an air bubble in the system, there will be less pressure, spongy-feeling brakes and longer stops. But that’s just the beginning. Left unattended, the car might not stop at all.
While you can fix this, there’s also a way to prevent it. Let’s look at when and how to bleed brakes.
When to Bleed Your Brakes
First, you’re not really bleeding brakes — you’re bleeding fluid and air out of the braking system, getting rid of air bubbles that might have formed before adding fresh brake fluid.
Here’s when you should bleed your brakes:
- When your brakes start to feel spongy.
- When stops are taking longer and feel less sure.
- If you find a leak. Leaks might not just let fluid out, they could also let air in. The only way to be sure your system doesn’t have an air bubble is to bleed your brakes after repairing the leak.
- If you’re replacing worn brake pads, which can cause air to enter the master cylinder. Braking with worn pads requires more brake fluid, which drains the reservoir and creates space for air.
- If you change your rotors or pads. Any brake job should include a brake bleed for safety’s sake.
- Once a year as part of good preventive maintenance.
How to Bleed Your Brakes
For all four methods you can use to bleed brakes, you’ll need a screwdriver for Torx screws (identifiable by the six-pointed groove in their head), however much fresh brake fluid your vehicle requires and a container to hold the old fluid.
Here are the four brake bleeding methods:
- Gravity: Put a container under the bleeder screw, open the screw and let gravity draw the old fluid into the container. Be prepared for some cleanup afterward. That fluid won’t fall in a straight line; instead, it will run down parts between the bleeder screw and the container.
- Manual:Put a container under the bleeder screw, and open it while another person slowly pushes and releases the brake pedal, forcing the fluid and air out. Work the brakes smoothly to avoid creating more air bubbles that might linger, contaminating the new fluid. Watch carefully to make sure the fluid coming out isn’t foamy — that’s a sign of new air bubbles being created.
- Pressure:Again, put a container under the bleeder screw and open it. Then, use a tank of pressurized brake fluid at the master cylinder to push the fluid and air through the system and out into the container.
- Vacuum:For this method, attach a vacuum bleeder to the bleeder screw after you open it. It draws the fluid and air out and into an attached container.
Whichever way you go, bleeding your brakes when you have a problem or as part of regular maintenance helps ensure that your braking system performs at its best and keeps you and your passengers safe.
Check out all the brake fluid available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on bleeding your brakes, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photos courtesy of Mike Hagerty.
Mike Hagerty is an automotive journalist whose work has been featured on radio, TV, in print and online since 1997. He's the Publisher and Editor of MikeHagertyCars.com, and contributes car reviews to the Los Altos Town Crier and losaltosonline.com. Previous outlets have included KFBK and KFBK.com in Sacramento, California, the ABC television affiliates and Hearst-Argyle and Emmis radio stations in Phoenix, Arizona; AAA magazines for Arizona, Oklahoma, Northwest Ohio, South Dakota and the Mountain West and BBCCars.com.