Upgrade Motorsport - Billet Alloy CNC Master Cylinder Bench Bleeding, System Bleeding & Torque Guide

Overview & Safety Notes

This guide covers how to properly bench-bleed, install, and bleed the full brake system using your Upgrade billet flange master cylinder. Correct procedure is vital to ensure firm, consistent pedal feel and eliminate trapped air.

Safety & Cautions Master Cylinder Bench Bleeding & System Bleeding

• Use fresh, quality brake fluid compatible with your system (e.g. DOT 3 / DOT 4)

• Avoid spilling fluid on painted surfaces, clean immediately if it happens

• Always keep reservoir topped during bleeding to prevent air ingress

• Use new copper washers on all fluid connections

Torque Specifications (Important)

Port	Thread	Tightening Torque	Washer Type
Fluid Inlet port	M10 × 1	17–20 Nm	Copper washer
Fluid Outlet port	M10 × 1	17–20 Nm	Copper washer

When tightening, do so gradually. Over-torquing can damage threads or distort sealing surfaces.

Bench Bleed (Before Installation)

Bench bleeding is essential, it removes air straight from the master cylinder bore before it’s even installed, making system bleeding far more effective.

Steps:

1. Mount the master cylinder securely by the flange in a vice (avoid clamping the bore portion).

2. Install bleeding fittings / plugs into the outlet ports (if removable caps are present) and connect clear hoses from those ports back into the reservoir. Ensure hose ends stay below fluid level.

3. Fill reservoir with fresh brake fluid (to ~¾ full).

4. Depress the piston smoothly with a blunt tool (e.g., dowel) in ~¾ to 1″ strokes, then release. Wait ~15 seconds between strokes for “quick-takeup” and avoid aeration.

5. Repeat until no air bubbles emerge in the hoses and the piston cannot be depressed more than ~⅛″.

6. Tap the master cylinder body gently (not the reservoir) to help dislodge any trapped bubbles.

7. Reinstall reservoir cap, remove from vice, and prepare for system installation.

   
   

4. Installation & System Bleed

Once bench-bled, install the master cylinder in your vehicle. Leave the bleed plugs installed until just before connecting lines.

Master Cylinder Bench Bleeding, System Bleeding & Torque Guide - Bleed the entire system:

• Begin bleeding at the brake furthest from the master cylinder and proceed progressively toward the nearest. This prevents pushing air backward into already bled lines.

• Use one of these methods: 

  • Manual pumping / two-person method: have someone pump while you open/close bleed nipples in sequence. 

  • Vacuum bleeding: use vacuum pump on bleed nipple to draw fluid through.

  • Pressure bleeding / flush: pressurise reservoir or use a pressure bleeder to push fluid through. (Useful for faster bleeding)

• Keep reservoir fluid topped at all times. Do not allow it to dip below the internal feed port.

• Once fluid runs clear, bubble-free, close each bleed nipple, torque them to spec, and check for leaks.

  
  

5. Final Checks & Testing

• Press the brake pedal and verify it feels firm, consistent, and free of sponginess.

• Inspect all lines, fittings, and the master cylinder itself for leaks.

• Perform a slow-speed brake test in a safe area to confirm full function before use.

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.