* Tips to remove air from the Hydraulic Control Unit*
** Air in the system can cause the ABS pump/HCU to stop working, which may be mistaken for a malfunctioning hydraulic control unit.
- The system operated fine as long as it was under pressure.
- However, as soon as the pressure was released, it reverted back to its previous state and Error codes returned.
Instructions for Bleeding Air from the Brake System of a Ford Escape (2000-2008) with C1477 or C1525 ABS Codes in the ABS Module:
1 - Choose the pressure method to eliminate air from the system: either suction at the calipers or pressurizing the brake fluid reservoir, or both.
2 - To pressurize the master cylinder, locate the hose attached to the cap of the reservoir.
3 - Prepare the tools for pressurizing the master cylinder:
- Option 1: Use an air compressor with a clamp-on air blow nozzle.
- Option 2: Use a hand pump.
- If using an air compressor, connect the air compressor line to the hose attached to the cap of the reservoir. Clamp on an air blow nozzle for a secure connection.
- If using a hand pump, connect the hand pump to the hose attached to the cap of the reservoir.
- Pressurize the master cylinder to 30 psi following the instructions provided for the chosen pressurizing method.
- To suck at the calipers, use a hand pump brake bleeder (e.g., Harbor Freight hand pump brake bleeder).
- Connect the hand pump brake bleeder to the calipers.
- Begin the bleeding process by using the hand pump brake bleeder to suck at the calipers.
- Continue sucking until a significant amount of air is released, especially from the front calipers.
- After bleeding, turn the key to activate the brake pump.
- Perform a system cycle by following these steps:
- Turn the key to the "on" position.
- Turn the key to the "off" position.
- Wait for 5 minutes.
- Listen for a hissing sound as fluid is released from the accumulator into the reservoir.
- Repeat this system cycle approximately 15 times to allow the pump and accumulator to purge air.
- Check for any warnings related to the ABS and the brake system. They should disappear after completing the bleeding process and the system cycle.
1. Note that air in the system can cause the ABS pump/HCU to stop working, which may be mistaken for a malfunctioning hydraulic control unit. The ABS pump activates when the key is turned on and intermittently during driving, producing a buzzing noise.
2. To remove air from the system, utilize two methods: suction at the calipers and pressurizing the brake fluid reservoir.
3. Pressurizing the master cylinder: Locate the hose attached to the cap of the brake fluid reservoir. Connect either an air compressor line with an air blow nozzle or a hand pump to the hose. Gradually pressurize the system to approximately 30psi.
4. Suction at the calipers: Use a hand pump brake bleeder. Attach the brake bleeder to the calipers. Utilize the hand pump to create suction and remove any trapped air within the system.
5. Combining both methods: Perform the pressurization process at the master cylinder first, ensuring the system is pressurized to 35 psi. Then proceed to suction at the calipers using the hand pump brake bleeder.
- Now Ensure the key is turned off and wait for approximately 4 minutes to let the Hydraulic Control Unit (HCU) in your car turn off.
- Turn the key back on to activate the HCU and start pressurizing the system.
- Set the pressure bleeder to 40 psi and connect it to the brake fluid reservoir.
- Apply pressure to the system using the pressure bleeder multiple times to help remove any remaining air. Repeat this step under pressure.
- Perform a bleed test to check for the presence of air in the system. If the system does not pass the test, repeat step 4 under pressure until it does.
- Keep in mind that the pressure applied by the pressure bleeder helps keep the air out of the HCU. When the pressure is released, the previous conditions may return.
- Use FORScan or a similar tool to perform another pressure bleed. This time, you may observe a significant amount of air coming out.
- Clear any error codes related to the brake system using the appropriate diagnostic tool.
- Run the air bleed test again to confirm that the system is free from any remaining air. The absence of error codes indicates a successful bleed.
- Test the brakes by driving and performing multiple stops over a few hours to ensure proper functionality.
Note: It is recommended to perform this procedure with a pressure bleeder before changing the motor.