How to bleed a brake system with ABS?

Purging air from an ABS-equipped braking system requires cycling the ABS pump/valve module in addition to bleeding each wheel, using the correct sequence and a brake fluid that matches the vehicle spec. With the right tools and a careful procedure, you can remove air from both the lines and the ABS modulator to restore firm braking.

Why ABS complicates bleeding

ABS systems include a hydraulic modulator and an electric pump that can trap air inside the ABS unit. Conventional bleeding of the master cylinder alone may not purge air from the ABS block. To fully purge air, you must activate the ABS pump/valves (via a scan tool or an ignition-on pump cycle) and then bleed the individual wheel circuits again as needed.

What changes with ABS

Bleeding in an ABS-equipped system often requires a dedicated ABS bleed step or tool-assisted pump cycling after the initial wheel bleeds. Always follow the vehicle’s service manual, as the procedure can differ between makes and models.

Tools and materials you’ll need

Assemble the equipment below to bleed an ABS-equipped braking system safely and efficiently.

• Correct brake fluid (DOT type as specified by the vehicle manufacturer)


• Clear plastic tubing and a leak-free bleeder bottle (with one-way valve if available)


• Brake bleeder wrench or flare-nut wrench for each bleed screw


• Vacuum or pressure brake bleeder (optional but recommended)


• ABS-capable scan tool or vehicle-specific diagnostic tool (for pump/valve cycling)


• Chocks, jack, and jack stands; wheel chocks for safety


• Rags, gloves, and eye protection


• Service manual for your exact make/model (for bleed order and ABS steps)

Having the right tools helps maintain a clean fluid system and ensures the ABS pump cycles without introducing contamination or air.

Recommended bleed sequence for ABS systems

Bleed the wheel cylinders in a sequence that follows the vehicle’s design, but a common and widely accepted approach is listed below. If your manual specifies a different order, follow that exactly.

1. Right front (RF)


2. Left front (LF)


3. Right rear (RR)


4. Left rear (LR)

Note: Some vehicles use a diagonal or alternate sequence. Always verify the exact order in your service manual or with a dealer. Completing the appropriate sequence helps move air away from the ABS modulator and toward the bleeder screws for expulsion.

Step-by-step bleeding procedure with ABS

Follow these steps to bleed an ABS-equipped braking system. If your vehicle supports an ABS bleed function on a scan tool, use it as directed by the tool’s instructions.

1. Park on a level surface, engage the parking brake, and place wheel chocks under the wheels that are not being bled. Keep the master cylinder reservoir filled to the “MAX” line with clean brake fluid of the correct DOT specification.


2. Attach a clear tube to the bleed screw of the first wheel in the chosen sequence and route the tube into a bleed bottle containing fresh fluid.


3. Have an assistant apply the brake pedal firmly and steadily to the floor, then hold it there.


4. Slowly loosen the bleed screw to allow fluid and air to escape. When a steady stream of fluid (without air pockets) flows, close the screw and have the pedal released slowly by the assistant.


5. Repeat steps 3–4 until you see a steady stream of fluid with no noticeable air bubbles. Refill the reservoir as needed to keep it within the safe range.


6. Move to the next wheel in the prescribed sequence and repeat the bleeding process.


7. After bleeding all four wheels,:
   - If you have an ABS tool: use the ABS pump/valve cycle function to actuate the pump and valves as commanded, then re-bleed the wheels if the tool indicates air may still be present.
   - If you don’t have a tool: turn the ignition to ON (engine OFF) and perform the ABS pump cycling per your manual or perform a few pedal pump cycles to prime the system, then re-bleed the final wheel(s) as needed.


8. Check the brake pedal for firmness. A properly bled system should have a firm pedal with minimal travel and no sponginess. If the pedal stays soft, re-check for leaks and repeating air from lines or the ABS module.


9. Once the pedal feels firm, remove all connections, reinstall caps, and torque all bleed screws to the manufacturer’s specification. Do a slow test drive to verify braking performance, avoiding hard stops until the system is confirmed working.

Proper cycling of the ABS pump is critical to remove trapped air within the ABS module. If you encounter persistent sponginess after repeating the steps and ABS cycling, a fault in the ABS module or a leak elsewhere in the system may exist and should be inspected by a professional.

Safety tips and common pitfalls

Take these precautions to reduce risk and improve success when bleeding ABS brakes.

• Always use the exact brake fluid type specified for your vehicle and avoid mixing fluids. Replace fluid that has absorbed water or contaminants.


• Never let the brake fluid level drop to the minimum line, especially during ABS cycling and bleeding.


• Keep the brake system clean; do not contaminate the fluid with dirt or old fluid from containers.


• Use proper tools to avoid rounding bleed screws (flare-nut wrenches are preferred).


• Follow the vehicle’s manual for the exact ABS bleed procedure and wheel order; some cars require a dedicated ABS bleed routine.


• If the ABS warning light remains on after bleeding, perform diagnostic checks for ABS fault codes and module integrity before driving.

Rushing a job or skipping the ABS cycle can leave air trapped in the system, resulting in a soft or spongy brake pedal and reduced stopping power.

What to check after bleeding

After completing the bleeding process, verify several aspects to ensure the system is functioning properly.

• Brake fluid level in the reservoir remains within the maximum mark.


• No leaks at any bleed screw or hose connections.


• ABS warning light is off after a normal ignition cycle or after a complete scan.


• Brake pedal firmness and consistent feel during a cautious road test.


• No unusual noises or pulling when applying the brakes.

If any issue persists, revisit the bleeding steps, inspect for leaks, or seek professional service to inspect the ABS module and associated hydraulic paths.

Summary

Bleeding brakes on ABS-equipped systems adds steps beyond conventional bleeding. Purge air from each wheel in the correct sequence, then activate the ABS pump/valve cycle (via a scan tool or ignition-based method) to purge trapped air from the ABS module. Maintain clean fluid, check for leaks, and verify pedal firmness with a cautious test drive. When in doubt, consult the vehicle’s service manual or a qualified technician to complete the procedure safely and correctly.

How to reset ABS braking system?

Disconnect the positive cable from your car battery, then let the electrical system's residual power drain by activating the headlight switch. This method can sometimes reset the ABS warning light. Or, use an OBD-II scanner to reset the ABS light.

Can air be trapped in an ABS module?

Some vehicles require a scan tool to activate the ABS pump. This tool circulates the fluid and dislodges air trapped within the ABS module.

Do I need a scan tool to bleed ABS brakes?

Yes, you can bleed ABS brakes without a scan tool, but it's more difficult and less thorough. You'll need to bleed the conventional brake system first, then activate the ABS pump by performing several hard stops on a loose surface like gravel to force the trapped air into the conventional lines. After activating the ABS, you will need to re-bleed the brakes again to remove any new air that has entered the system. 
Step 1: Perform a standard brake bleed 

• Bleed the brakes as you normally would, following the correct bleeding sequence for your vehicle (usually starting with the wheel furthest from the master cylinder). 
• Be careful not to let the master cylinder run dry, as this is a common way air enters the ABS system. 

Step 2: Activate the ABS 

• Drive the vehicle to a safe, loose surface like a dirt or gravel road. 
• Accelerate to a moderate speed and then slam on the brakes to activate the ABS. You'll feel the pedal pulsate and hear the system working. 
• You may need to do this several times to force all the air out of the ABS hydraulic unit. 

Step 3: Re-bleed the brakes 

• After activating the ABS, the brake pedal will likely feel soft, indicating air has been pushed into the conventional lines.
• Return to a safe location and repeat the standard brake bleeding procedure.
• Test the brakes again to ensure the pedal is firm and the air has been completely purged. 

Important considerations

• Some modern systems are more complex and may require a scan tool to properly flush the fluid from the ABS accumulator. 
• If the pedal remains soft after repeating this process, it's best to use a scan tool to perform a full ABS service, as recommended by the manufacturer. 
• If you're performing major brake work, such as replacing a caliper or master cylinder, the scan tool method is often recommended for a more thorough flush. 

Can you bleed brakes with ABS?

At Brakes-Shop.com, our experts know that tackling an ABS-equipped vehicle's brake system doesn't have to be intimidating. Years of hands-on experience and rigorous testing have shown that, for most vehicles, the process is straightforward and nearly identical to bleeding a non-ABS system.