« Back to Dictionary Index
“Bench bleeding” is a procedure used to remove air from a new or rebuilt master cylinder before it is installed in a vehicle’s hydraulic brake system. Here’s how bench bleeding works and why it’s important:
- Purpose:
- The primary goal of bench bleeding is to ensure that the master cylinder is properly filled with brake fluid and free of any air bubbles. Air bubbles can compress, leading to a spongy brake pedal feel and reduced braking performance.
- Procedure:
- Setup: The master cylinder is mounted securely on a workbench or in a vise, typically in an upright position to facilitate bleeding.
- Filling: Brake fluid is poured into the reservoirs of the master cylinder, ensuring that the fluid level covers the ports and internal components.
- Bleeding: Special bleeding kits or tubes are attached to the master cylinder’s outlet ports (where brake lines will be connected). These tubes are submerged in a container filled with brake fluid.
- Pumping: The piston inside the master cylinder is then operated manually, either by pressing the brake pedal (if still attached to a vehicle) or by using a special tool to simulate pedal movement. This action forces brake fluid through the cylinder, displacing any trapped air bubbles.
- Repeat: The bleeding process is repeated until all visible air bubbles are expelled from the brake fluid exiting the tubes. It may take several cycles to ensure thorough bleeding.
- Advantages:
- Bench bleeding is effective because it allows mechanics to purge air from the master cylinder in a controlled environment, ensuring that the cylinder is filled with brake fluid and ready for installation.
- It reduces the likelihood of introducing air into the brake system during master cylinder installation, which could necessitate additional bleeding and potentially compromise brake performance.
- Bench bleeding is commonly performed during the installation of a new master cylinder or after rebuilding an existing one. It is a standard procedure recommended by vehicle manufacturers and brake system service manuals.
In summary, bench bleeding is a critical procedure in brake system maintenance, ensuring that the master cylinder is properly filled with brake fluid and free of air bubbles before it is installed in a vehicle. This helps maintain brake system integrity and ensures optimal braking performance.
« Back to Dictionary Index