All vehicular components get damaged due to general wear and tear. Some have consequences that are more extreme than others, such as faulty braking systems.
It’s imperative to be knowledgeable about ways to repair vehicle components. One method often used for a faulty brake system is called brake bleeding.
What Does Bleeding the Brakes Mean?
Bleeding the brakes removes any excess air trapped in the hydraulic system. Air gets into the system for different reasons:
- An open hydraulic brake line or unit
- Through small holes or loose brake line connections
- Absorption of moisture by the brake fluid
- Boiling brake fluid due to severe braking
What Is the Importance of Brake Bleeding?
Trapped air causes your brake to feel soft, making it harder to stop your vehicle. It can lower the position of the brake pedal, requiring you to pump it multiple times before coming to a halt. Bleeding the brakes makes the system more efficient and easier to use.
What Does Bleeding the Brakes Entail?
The most common way to do the procedure is by manually bleeding the brakes. This process involves two people working together to replace the brake fluid. Here’s what you can expect when having your brakes bled:
- Step 1: The car is turned off while pumping the brake pedal to discharge the vacuum or hydraulic power.
- Step 2: The master cylinder reservoir is refilled with new brake fluid (at least half full).
- Step 3: A plastic hose is attached over the bleeder screw of the first wheel cylinder or brake caliper. They’ll start with the wheels furthest from the master cylinder. It generally goes right rear, left rear, right front, then left front.
- Step 4: The other end of the hose is submerged in a separate jar filled with brake fluid.
- Step 5: The assistant presses the brake pedal three times, holds, then opens the bleeder valve and watches for air bubbles passing through the fluid. Once there aren’t any visible bubbles, they’ll close the bleeder before moving to the next wheel.
- Step 6: Lastly, the assistant tightens the bleeder screw and slowly releases the brake pedal.
Note your car needs to be off whenever you bleed the brakes, no matter the method used. Additionally, certain vehicles require specific procedures for bleeding for it to work properly. They’ll also use a scan tool for certain procedures.
Certain vehicles require specific procedures for bleeding for it to work properly. They’ll also use a scan tool for certain procedures.–Anthony Harlin, ASE Certified Master Automobile Technician
Other Ways to Bleed the Brakes
Besides manual bleeding, there are different ways to bleed the brakes. All of them have their advantages and disadvantages. Here are some of the other methods:
Gravity bleeding is a slower process than manual bleeding. It involves opening the bleeder valve and waiting until the brake fluid flows out. The trapped air rises and escapes from the port through the valve. Here is the more comprehensive step-by-step process for how mechanics gravity bleeds the brakes:
- Step 1: The master cylinder reservoir is filled with new brake fluid. The level is constantly checked to ensure it’s half full.
- Step 2: Plastic tubings are attached to each bleeder screw in jars.
- Step 3: The bleeder screws are open to ensure the fluid and air begins drains.
- Step 4: The mechanics will wait for tiny bubbles to form into larger bubbles.
- Step 5: The bleeder screws are closed and the cylinder reservoir is filled with brake fluid to its capacity.
Note gravity bleeding may be the most ineffective way to bleed the brakes.
Only one mechanic is needed to work on the vehicle, and they can do all four wheels simultaneously.
It’s a slower process that takes an hour or more. Additionally, gravity bleeding doesn’t work on brake systems with residual pressure check valves as they restrict the flow of the fluid.
Pressure or power bleeding is a method that attaches a pressure bleeder to the master cylinder to force brake fluid through the system. The pressure created by the bleeder removes the trapped air. Here is the commonly followed process for pressure bleeding:
- Step 1: They’ll then clean the top of the master cylinder and the gasket surface.
- Step 2: New brake fluid is added to the reservoir, and a pressure bleeder adapter is installed on the master cylinder.
- Step 3: The pressure bleeder is filled and sealed with the correct type of brake fluid.
- Step 4: The pressure bleeder supply hose is connected to the adapter.
- Step 5: The bleeder is pressurized up to 30 pounds per square inch (PSI), then they’ll override the metering valve.
- Step 6: The fluid supply valve on the bleeder is opened to allow the pressurized brake fluid to enter the system.
- Step 7: One end of the plastic hose is slipped over the bleeder screw of the wheel cylinder or brake caliper, while the other end is submerged in a jar filled with brake fluid.
- Step 8: The bleeder screw is opened one-half turn for the fluid to run. This remains open until no air bubbles emerge.
- Step 9: Afterwards, the metering valve override tool is removed and the fluid supply valve on the pressure bleeder is closed.
- Step 10: They’ll remove the master cylinder adapter and disconnect the supply hose.
- Step 11: Lastly, they’ll add brake fuel up to the reservoir’s max capacity.
Pressure bleeding is by far the most effective method and yields the fastest and most accurate results.
Vacuum bleeding uses a suction pump to create a low-pressure area at the bleeder screw that forces the brake fluid through the system when the screw is opened. Expect the following steps to be done:
- Step 1: The master cylinder reservoir is filled halfway with new brake fluid.
- Step 2: A plastic tube is attached from a vacuum bleeder to the bleeder screw.
- Step 3: The vacuum is turned on to create a partial vacuum in the catch bottle.
- Step 4: The bleeder screw is loosened to let the brake fluid and air bubbles flow into the bottle.
Only requires one mechanic to perform the procedure. Additionally, the steps are easy to follow, and the required equipment is inexpensive.
The vacuum tool often draws air into the line between the bleeder valve and the hose, which creates bubbles interpreted as air. Therefore, it might not be as efficient as the other methods.
How Much Does It Cost to Bleed the Brakes?
The average price of brake bleeding ranges from $80 to $110, depending on the year, make, and model of your vehicle.
There are also DIY brake bleeder kits you can purchase. One-man kits go for as low as $8, while universal ones go for as high as $220.
Can You Bleed the Brakes Yourself?
It’s possible to bleed the brakes yourself with the right tools and adequate know-how. Alternatively, you may save time and effort by bringing your vehicle to an auto shop and letting a mechanic diagnose and repair your brake system.
You can also check out this video for tips on how to bleed the brake fluid system:
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.