How to Bleed Your Car’s Brakes
What You Need to Know
- When air gets into brake fluid it works less effectively.
- Bleeding your brakes is simply a matter of removing air from the fluid.
- You’ll need to jack up your car and remove the wheels before bleeding.
- You’ll also need a 10mm spanner, a bleeding kit and a helper.
- You should bleed the back brakes first, then the front ones.
- Be sure your helper gets their timing right when pumping the brakes, or you could let more air into the system.
- Be sure to top up the fluid in the reservoir once you’ve bled out all the air bubbles form each brake.
- When finished, take a gentle test drive to ensure all is working as it should.
Keeping your car in good shape is vitally important for you safety and, as repairs can be costly, a little maintenance can help save you a fair bit of cash. Prevention, as they say, is better than cure. Of course, your brakes are paramount when it comes to avoiding unnecessary accidents. Knowing how to bleed your brakes can help keep them working to full effect.
Why Do I Need to Bleed My Brakes?
Even if you’re not au fait with the inner workings of your car, you’re probably aware that brakes use fluid. This fluid is what actually disperses the pressure that stops the wheels when you put your foot to the pedal. If air gets into this fluid the brakes will work less effectively as air is easier to compress than fluid (imagine hitting a punching bag full of water, compared to one full of air). As a result, you’ll need to break harder to get the same stopping force.
Air can get in when brake pads have become worn and will contaminate the fluid, causing problems. Just as when you bleed a radiator, bleeding your brakes is all about getting air out of the system to keep it working at optimum efficiency. So, how do you do it?
Bleeding Your Brakes
To bleed your brakes you’ll need a brake bleeding kit, a helper, and a 10mm spanner.
First you’ll need to jack up your car to get it off the ground and then remove the wheel that you’re going to do first. (The exact order you bleed each brake isn’t important, but you should to the back ones first, then the front.) If you aren’t sure how do to this, check out our guide to changing a tyre. The process is explained under the heading ‘Changing the Wheel’.
Once you have the wheel removed, you’ll need to apply your spanner to the bleed screw. If you don’t know what that looks like, you can find an image here. Fit your spanner to the screw but do not loosen yet.
Fit the tube of your bleeding kit over the end of the bleed screw, ready for the fluid to flow into it. Next, get your assistant to pump the brakes three times then to hold the brake pedal down until further notice. At this point you can loosen the screw and release the fluid. After about a second or so, tighten the screw again, but only gently. Only once the screw is tightened can your helper take their foot off the brake pedal. If you mis-time things and have the brakes released before the screw is closed, you may allow air back into the system, defeating the purpose of the exercise.
If you check the fluid in the pipe you’ll see it contains those problematic air bubbles described at the start of the article. You need to repeat the bleeding process on each break until the fluid coming out is free of bubbles. This will take between five to ten run throughs.
Once you’ve done this you’ll need to top up your brake fluid. If the level in the reservoir gets too low air can be sucked into the system, undoing all your good work up to this point.
If you’re unsure how to go about topping up your brake fluid, we’ve covered it in our guide to car maintenance. (Look under the header ‘Check Brake Fluid Level’).
Once You’re Done
Be sure to re-tighten the bleed screw and reattach the wheels securely. Who should instantly notice that the brakes are more responsive, even when stationary. T o make sure they are working well go for a short drive, without reaching any great speed and see how they feel.
- Brakes are one of the areas looked at in an MOT. Find out more here.
- The Tyre and Autocentre Group can service your car if the problem is out of your range.
- Find yourself a cheaper car insurance quote here.