When car brakes aren’t working as well as they could, there are a few possible explanations. Needing to get your brake pads replaced is probably the most common reason, but sometimes, you might notice a spongy feel when you step on the brakes, even with brand new brake pads. In this case, you may be able to solve the problem by bleeding your brakes.
Bleeding brakes can help restore full braking strength when air bubbles have gotten caught in the brake lines. Your car’s hydraulic braking system uses the pressure of the brake fluid in those lines to increase the force applied by your foot so that it is strong enough to stop the car. If there are any air bubbles in the brake fluid, it will reduce the effectiveness of the brakes.
So, if your brakes feel spongy when you press on the pedal, this may be the solution. In this post, we’ll show you how to bleed brakes, and offer some tips to keep your brakes working at their best.
How to bleed brakes: Materials
You will need a few supplies in order to bleed your brakes, and you will need an assistant to press on the brake pedal while you handle the brake lines. Before you begin, make sure you have:
- Plenty of fresh brake fluid
- A clean turkey baster
- A lint-free rag
- A box-end wrench (5/16” or as specified by your car’s owner’s manual)
- Plastic aquarium tubing (diameter should fit over your car’s bleeder bolts)
- A small, clear plastic bottle
- A 1×4 wooden board
- Suitable clothing and shoes
How to bleed brakes: Cleaning the master cylinder
Before you can start bleeding your brakes, you need to clean out the master cylinder reservoir and fill it with clean brake fluid. To do this:
- Unscrew the top of the master cylinder reservoir. The reservoir is usually light-colored with a black cap, in the engine compartment of your car.
- Use the turkey baster to remove as much of the old brake fluid in the reservoir as possible. Be careful not to get brake fluid onto any painted surfaces on your car, because it will eat through the paint very quickly.
- Then, use the rag to clean out any sediment that might be in the master cylinder reservoir.
- If any brake fluid spills, you can clean it up with soap and water, or special brake-cleaning fluid if you have it on hand.
- Fill the reservoir up with clean brake fluid and screw the top back on.
- Finally, pump the brake pedal about 15-20 times to flood the lines with fluid.
How to bleed brakes: Preparing the bleeder valves
Now that you have cleaned the master cylinder, it’s time to prepare a few things so that you can move onto bleeding the brake lines.
- Use the box-end wrench to loosen the bleeder valves on all four wheels, but without opening them.
- Also, get the small plastic bottle ready by pouring in a couple inches of clean brake fluid.
- Place the wooden board underneath the brake pedal to act as a spacer. This will protect the master cylinder from being damaged by the internal pistons bottoming out.
- Top off the master cylinder reservoir with more clean brake fluid, close it, and keep an eye on it throughout the next section. It should always be full while bleeding the brake lines in order to keep air from getting into the system.
- Call your assistant over. Their job starts in the next section!
How to bleed brakes: Bleeding the brake lines
Each wheel has its own brake line, and they need to be bled individually, in this order: rear passenger side, rear driver’s side, front passenger side, front driver’s side.
Here are the steps to follow for each wheel:
- Push one end of the plastic aquarium tubing over the bleeder bolt.
- Place the other end of the tubing in the brake fluid that you put in the small plastic bottle. This is needed to prevent air from being sucked back up into the brake lines.
- Your assistant should sit in the driver’s seat and press down on the brake pedal with slow, even force, as if they were trying to stop for a stop sign. When the pedal is all the way down, have them say “down” to let you know.
- Use the box-end wrench to turn the bleeder bolt a quarter turn to the left, loosening it.
- Wait for the old brake fluid to stop flowing through the tubing and into the small bottle.
- Use the box-end wrench to close the bleeder bolt again (turning to the right).
- Tell your assistant they should allow the brake pedal to come back up, by saying “up”, for example.
- Repeat Steps 3–7 until you see clean brake fluid coming through the tubing. Top off the master cylinder reservoir with more fluid every few times the brake pedal goes down and up again.
- Once the brake fluid is coming out clear through the tubing on the bleeder valve of the first wheel, use the box-end wrench to tighten the bolt back up before moving onto the second wheel.
- Repeat this entire process for each wheel in the order indicated.
After your have tightened up the bleeder bolt on the last wheel, your brakes have been bled and you are all finished.
If you continue to experience problems with your braking system even after bleeding, it’s time to consult a professional.