Upgrade Motorsport - Master Cylinder Bleeding & Bench-Bleed Guide

Grant Lockhead
Oct 9
2 min read

Updated: 3 days ago

Applicable - Master Cylinder Bleeding & Bench-Bleed Guide

.625 Cast Aluminium Body (Girling type)
.700 Cast Aluminium Body (Girling type)
.750 Cast Aluminium Body (Girling type)

These versions share similar internal design principles and identical bleeding procedures.

Three images of a metal hydraulic cylinder with black rubber accordion seals and yellow nozzles, on a white background.

Why Bench Bleeding Is Essential

Before installing the master cylinder in your vehicle, you must bench bleed it. This process removes trapped air within the bore and ports that cannot be purged easily once installed. Skipping this step can leave air bubbles inside the master cylinder, leading to a soft pedal, uneven hydraulic pressure, and poor brake performance.

Following this Master Cylinder Bleeding & Bench-Bleed Guide ensures that:

The master cylinder begins air-free and ready for system bleeding
Pedal travel remains firm and consistent
Downstream bleeding is more effective and faster

Bleeding & Bench Procedure (for all 3 MC versions)

1. Preparation & Setup

Secure the master cylinder in a vice by its mounting flange (never clamp the bore).
Fit the reservoir (if separate) and fill it approximately three-quarters full with clean brake fluid.
Attach clear bleed hoses to each outlet port and submerge the hose ends back into the reservoir fluid.

2. Bench Bleed

Depress the piston slowly by hand (~½ to 1 inch per stroke), then release.
Pause briefly between strokes (5–15 seconds) to allow air to rise.
Continue until no bubbles appear in the hoses.
Tap the body lightly to release trapped air if necessary.
When fluid flows clean and bubble-free, the master cylinder is ready to install.

3. Install in Vehicle & Connect Lines

Mount the master cylinder in its correct position.
Connect inlet and outlet lines securely, using proper fittings and washers.
Top up the reservoir to maintain adequate fluid levels.

4. System Bleeding (Vehicle Brake System)

Bleed the brakes starting from the wheel furthest from the master cylinder.
Use either manual, vacuum, or pressure bleeding.
Keep the reservoir topped up throughout.
Continue until all air is expelled and the pedal feels firm.

5. Final Checks

Inspect all connections for leaks.
Confirm consistent pedal pressure and travel.
Test the brakes gently in a safe environment before full operation.

A gray hydraulic brake cylinder with a black rubber boot and yellow connectors rests on a white background.

Important Reminders

Always use fresh, compatible brake fluid (DOT 4 or as specified).
Never allow the reservoir to run dry during bleeding.
Replace copper washers each time fittings are loosened.
Avoid over-tightening any fittings.
Re-check connections and fluid levels after testing.

Safety and Installation Disclaimer

Upgrade Motorsport products are designed for use in competition and specialist vehicles that vary significantly in size, weight, configuration, and application. The responsibility for correct installation, suitability, and safe use lies entirely with the purchaser and/or installer.

Upgrade Motorsport and any member of its team accept no legal liability or responsibility for any accidents, incidents, damages, personal injury or death proven to be caused by or related to the use of any component supplied by Upgrade Motorsport.These products are installed in diverse motorsport and automotive environments, and it is the sole responsibility of the end user to ensure compatibility, compliance, and safe operation. All installations should be carried out by a qualified professional.