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How do I bench bleed a Master Cylinder ?

Before you install your new or rebuilt Master Cylinder on you car you will want to bench bleed it. This will remove all the air from the master cylinder to eliminate a possible spongy pedal feel. First clamp the master cylinder in a vise. Attach the fittings and hoses provided with the new master cylinder and connect the hoses having routed them back into the reservoir. Fill the reservoir with brake fluid. Pump the master cylinder slowly with a screw driver until all the air bubbles stop coming up then your done.


In Car Bleeding Procedures


  1. Fill the master cylinder reservoirs.
  2. Place absorbent rags under the fluid lines at the master cylinder.
  3. Have an assistant depress and hold the brake pedal.
  4. With the pedal held down, slowly crack open the hydraulic line fitting, allowing the air to escape. Close the fitting and have the pedal released.
  5. Repeat Steps 3 and 4 for each fitting until all the air is released.