A Scan Tool is required to perform the following procedure.
- Raise the vehicle in order to access the system bleed screws.
- Bleed the system at the right rear wheel first.
- Install a clear hose on the bleed screw.
- Immerse the opposite end of the hose into a container partially filled with clean DOT 3 brake fluid.
- Open the bleed screw 1 / 2 to one full turn.
- Slowly depress the brake pedal. While the pedal is depressed to its full extent, tighten the bleed screw.
- Release the brake pedal and wait 10-15 seconds for the master cylinder pistons to return to the home position.
- Repeat the previous steps for the remaining wheels. The brake fluid which is present at each bleed screw should be clean and free of air.
- This procedure may use more than a pint of fluid per wheel. Check the master cylinder fluid level every four to six strokes of the brake pedal in order to avoid running the system dry.
- Press the brake pedal firmly and run the Scan Tool Automated Bleed Procedure. Release the brake pedal between each test.
- Bleed all four wheels again. This will remove the remaining air from the brake system.
- Evaluate the feel of the brake pedal before attempting to drive the vehicle.
- Bleed the system as many times as necessary in order to obtain the appropriate feel of the pedal.
When adding fluid to the brake master cylinder reservoir, use only DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.
Avoid spilling brake fluid onto painted surfaces, electrical connections, wiring, or cables. Brake fluid will damage painted surfaces and cause corrosion to electrical components. If any brake fluid comes in contact with painted surfaces, immediately flush the area with water. If any brake fluid comes in contact with electrical connections, wiring, or cables, use a clean shop cloth to wipe away the fluid.
The base hydraulic brake system must be bled before performing this automated bleeding procedure. Refer to Bleeding the Brake System procedure in the Brake Operating System section of this manual before proceeding.
- Connect a scan tool to the vehicle-s Data Link Connector (DLC).
- Start the engine and allow the engine to idle.
- Depress the brake pedal firmly and maintain steady pressure on the pedal.
- Using the scan tool, begin the automated bleed procedure.
- Follow the instructions on the scan tool to complete the automated bleed procedure. Release the brake pedal between each test sequence.
- Turn the ignition OFF .
- Remove the scan tool from the vehicle.
- Fill the brake master cylinder reservoir to the maximum-fill level with DOT-3 brake fluid from a clean, sealed brake fluid container.
- Bleed the hydraulic brake system. Refer to Bleeding the Brake System procedure in the Brake Operating System section of this manual.
- With the ignition OFF , apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
- Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
- If the brake pedal feels spongy, repeat the automated bleeding procedure. If the brake pedal still feels spongy after repeating the automated bleeding procedure inspect the brake system for external leaks.
- Turn the ignition key ON but DO NOT start the engine; check to see if the brake system warning lamp remains illuminated.
- If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired.
- Drive the vehicle to exceed 8 mph (13 kph) to allow ABS initialization to occur. Observe brake pedal feel.
- If the brake pedal feels spongy, repeat the automated bleeding procedure until a firm brake pedal is obtained.
Automated Bleed Procedure
In most circumstances a base brake bleed is all that is required for most component replacements (such as wheel cylinders, calipers, brake tubes, and master cylinder) except for Brake Pressure Modulator Valve (BPMV) replacement.
The following automated ABS bleed procedure is required when one of the following occur:
Manual bleeding at the wheel cylinders does not achieve the desired pedal height or feel.BPMV replacementExtreme loss of brake fluid has occurred.Air ingestion is suspected.
- If none of the above conditions apply, use standard bleed procedures.
- The auto bleed procedure is used on BOSH 5.3 equipped vehicles. This procedure uses a scan tool to cycle the system solenoid valves and run the pump in order to purge the air from the secondary circuits. These secondary circuits are normally closed off, and are only opened during system initialization at vehicle start up and during ABS operation. The automated bleed procedure opens these secondary circuits and allows any air trapped inside the BPMV to flow out toward the wheel cylinders or calipers where it can be purged out of the system.
- Inspect the battery for full charge, repair the battery and charging system, as necessary.
- Connect a scan tool to the data link connector (DLC) and select current and history DTCs. Repair any DTCs prior to performing the ABS bleed procedure. Inspect for visual damage and leaks and repair, as needed.
- Raise and vehicle on a suitable support.
- Turn the ignition switch to the OFF position.
- Remove all 4 tires.
- Connect the pressure bleeding tool according to the manufacturer's instructions.
- Turn the ignition switch to RUN position, engine off.
- Connect a scan tool and establish communications with the ABS system.
- Pressurize the bleeding tool to 30-35 psi (206-241 kPa).
Performing the Automated Bleed Procedure
NOTEThe Auto Bleed Procedure may be terminated at any time during the process by pressing the EXIT button. No further Scan Tool prompts pertaining to the Auto Bleed procedure will be given. After exiting the bleed procedure, relieve bleed pressure and disconnect bleed equipment per manufacturers instructions. Failure to properly relieve pressure may result in spilled brake fluid causing damage to components and painted surfaces.
- With the pressure bleeding tool at 30-35 psi (206-241 kPa), and all bleeder screws in closed position, select Automated Bleed Procedure on the scan tool and follow the instructions.
- The first part of the automated bleed procedure will cycle the pump and front release valves for one minute. After the cycling has stopped the scan tool will enter a cool down mode and display a 3 minute timer. The auto bleed will not continue until this timer expired, and cannot be overridden.
- During the next step, the scan tool will request the technician to open one of the bleeder screws. The scan tool will then cycle the respective release valve and pump motor for one minute.
- The scan tool will repeat step 3 for the remaining bleeder screws.
- With the bleeder tool still attached to the vehicle and maintaining 30-35 psi (206-241 kPa), the scan tool will instruct the technician to independently open each bleeder screw for approximately 20 seconds. This should allow any remaining air to be purged from the brake lines.
- When the automated bleed procedure is completed the scan tool will display the appropriate message.
- Install all 4 tires.
- Remove pressure from the pressure bleeding tool and then disconnect the tool from the vehicle.
- Depress the brake pedal to gage pedal height and feel. Repeat steps 1-8 until the pedal is acceptable.
- Remove the scan tool from the DLC connector.
- Lower the vehicle.
- Inspect the brake fluid level in master cylinder.
- Road test the vehicle while making sure the brake pedal remains high and firm.
- If the vehicle is equipped with a traction control system (TCS), the scan tool will cycle both the ABS and the TCS solenoid valves. This bleed procedure is the same as above.