Master Cylinder Bench Bleeder
A kit of fittings and hoses used to purge air from a new master cylinder before it is installed on the vehicle.
A master cylinder bench bleeder is a kit consisting of plastic fittings, hoses, and clips used to purge air from a new or rebuilt brake master cylinder before it is bolted to the vehicle. The master cylinder has deep internal chambers that trap large amounts of air. Trying to bleed this air out after installation using the standard pedal-pump method is extremely slow and can damage the brake booster or push air deep into the ABS valving.
To bench bleed, the master cylinder is clamped in a vise (bench). The plastic fittings are screwed into the outlet ports, and clear tubes are routed from the fittings back up into the master cylinder's reservoir, which is filled with fresh brake fluid. A rod is then used to manually push the cylinder piston, pumping fluid through the tubes and bubbling air out of the reservoir until only solid fluid circulates.
Once bench bleeding is complete and no bubbles are visible in the tubes, the hoses are disconnected, the ports are plugged, and the master cylinder is quickly installed on the vehicle. This process ensures a firm brake pedal from the start and makes the final system bleeding much faster and more effective.