Preliminary Information
Brake System BleedingThe ABS/TCS System must be bled any time that air is permitted to enter the hydraulic system due to disconnection of hydraulic pipes or hoses. It is important to note that air in the hydraulic system will not cause a spongy pedal feel or additional pedal travel. The Bosch Anti-Lock Brake System monitors booster piston travel and boost pressure and may set a diagnostic trouble code due to air in the brake system. Refer to Testing and Inspection for additional information regarding ABS self-diagnosis.
ABS bleeding information is divided into three parts, including:
- Pump and Booster Bleeding
- Pressure Bleeding of Wheel Circuits and Master Cylinder
- Manual Bleeding of Wheel Circuits and Master Cylinder
The pump and booster must be bled if service is performed which involves removal of the pressure hose (pump to hydraulic unit), return hose (hydraulic unit reservoir to pump) or pump/motor assembly. The pump and booster also must be bled if the reservoir has been emptied or removed.
The individual wheel circuits must be bled if any hose or pipe fittings has been disconnected or if any caliper has been removed from the car. If it becomes necessary to bleed the pump and booster, it may also be necessary to bleed all wheel circuits. Wheel circuits may be bled manually or with a pressure bleeder. Both procedures are described below.
Important
^ During bleeding operations, be sure that the brake fluid level remains close to the FULL mark on the reservoir. Check the fluid level periodically during the bleeding procedure and add DOT 3 brake fluid as required.
^ Do not allow the pump to run continuously for more than 60 seconds. If it becomes necessary to run the pump for a period of time exceeding 60 seconds, allow several minutes for the pump to cool after each 60 second run.