Hydraulic brake booster » Bleeding


How to Bench Bleed your Master Cylinder:

Bench bleed the master cylinder before installation on the vehicle. Bench bleeding removes air from the master cylinder. Bench bleeding reduces the time required to bleed the brakes after installation.

  1. Plug the outlet ports. Mount the master cylinder in a vise with the front end slightly down. -- Never clamp the bore in a vise. Use the mounting flange ears when clamping the master cylinder in a vise.
  2. Fill the master cylinder reservoir with clean brake fluid.
  3. Stroke the primary piston about 1" (25mm) several times using a smooth round-end tool. The primary piston will not travel the full 1" stroke as air bleeds from the master cylinder.
  4. Reposition the master cylinder in the vise with the front end tilted slightly up.
  5. Stroke the primary piston about 1" several times again.
  6. Reposition the master cylinder level in the vise.
  7. Loosen the plugs in the outlet ports one at a time. Then push the piston into the bore in order to force the air from the cylinder.
  8. Tighten the plug(s) before allowing the piston to return to its original position. This prevents air from being drawn back into the cylinder.
  9. Fill the master cylinder reservoir with clean brake fluid.
  10. Follow normal bleeding procedures after install the master cylinder.


After bleeding the master cylinder be sure to bleed your brakes according to normal procedures. Refer to your vehicle manual.


Installation Tips:

  1. Under no circumstances do you bleed this system with the engine running.
  2. Under no circumstances should you EVER manually pull the brake pedal up from the floor or you will render the Hydraulic brake booster inoperable.
  3. If you replace your master cylinder you must first bench bleed it and then bleed your brake system prior to bleeding the Hydraulic brake booster system.


If you have a filthy fluid situation and it requires flushing due to problems that have developed (believe me, there is crud in your steering box) here are directions for that and part numbers for filters to use.


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