This bleeding procedure is only applicable for the anti-lock brake modulator unit; bleeding of the master cylinder and wheel cylinders/brake calipers should be performed the same as vehicles without anti-lock systems.
A Diagnostic Readout Box (DRB), or the equivalent type of scan tool, is essential to perform the bleeding of the ABS system.
The brake system must be bled any time air is permitted to enter the system through loosened or disconnected lines or hoses, or anytime the modulator is removed. Excessive air within the system will cause a soft or spongy feel in the brake pedal.
When bleeding any part of the system, the reservoir must remain as close to full as possible at all times. Check the level frequently and top off fluid as needed.
The Bendix Anti-lock 4 brake system must be bled as 2 separate brake systems. Proper procedures must be followed if the system is to work correctly. The normal portion of the brake system is bled in the usual fashion with either pressure or manual bleeding equipment and must be fully and properly bled before bleeding the modulator.
To bleed the hydraulic circuits of the brake system modulator assembly, the aid of an assistant will be required to pump the brake pedal.
The Bendix 4 anti-lock brake system modulator does not need to be bled when doing normal servicing procedures such as caliper, hose or wheel cylinder replacement. The modulator does need to be bled when the modulator is removed or the lines are disconnected from the modulator. When servicing this system use DOT 3 brake fluid.
- Assemble and install all brake system components on the vehicles, making sure all of the hydraulic lines are installed and tightened properly.
- Connect the DRB or equivalent scan tool to the data link connector, located under the dash panel, near the steering column cover.
- Use the scan tool to check if there are any Diagnostic Trouble Codes (DTCs) stored. If any codes are present, they must be removed prior to bleeding the system.
- Fill the master cylinder reservoir to the proper level.
- Bleed the base brake system using the pressure or manual methods outlined earlier in this section.
- Using the DRB or equivalent scan tool, go to the "Bleed ABS" routing. Apply the brake pedal firmly, then initiate the "Bleed ABS" cycle one time. Release the brake pedal.
- Properly bleed the base brake system again.
- Repeat steps 6 and 7 until the brake fluid flows clear and free of bubbles. Check the brake fluid level in the reservoir periodically to prevent the reservoir from running low on fluid.
- Road test the vehicle to check for proper brake system operation.