Aluminum Master Cylinder Conversion

IMPORTANT: Make sure to read and understand this article completely before starting installation. If you are not experienced with working on your vehicle, please consult a qualified ASE technician. We are not responsible for any damage caused to you or your vehicle due to improper installation.

  1. Remove any existing master cylinder. If you are installing an aftermarket master cylinder, remove the hard lines running from it.
  2. Bench bleed the new master cylinder. This is necessary because if you try to do this while it is in the vehicle; it will be very difficult is not impossible to get all of the air out of the system.

    1. Clamp the master cylinder mounting flange in a vise. Do not clamp the master cylinder by the body. Position the master cylinder to be sure it is perfectly level.
    2. Install and tighten the bench bleeder fittings into the master cylinder outlet ports.
    3. Attach a section of plastic tubing over the ends of each barbed fitting. Place the bleeder tube positioning clip in the top of the reservoir and insert the open end of each tube through the positioning clip.
    4. Fill the reservoir with clean, fresh brake fluid. Check the ends of the clear tubing are fully submerged in the brake fluid. Use a long Phillips head screwdriver to slowly depress and release the master cylinder plunger, using 3A” to 1″ strokes. Using slow even strokes, stroke the master cylinder until no bubbles are present in the lines and master cylinder.
    5. Sometimes tapping the bottom of the master cylinder will help to bleed air out. Make sure to bleed the system until no air bubbles are present. Pressing and releasing the plunger too fast will cause brake fluid to spray from the reservoir and air may enter the system. Top up the fluid reservoir as needed.
    6. Once there are no more air bubbles visible, remove the bleeder tubes and positioning clips.
    7. Install the master cylinder cap.
  3. Using the 2 original bolts mount the new master cylinder to the firewall.
  4. If you are installing an aftermarket master cylinder, you will need to adapt the stock lines to the new location of the ports. However, if the new ports are on the opposite side of the master cylinder, new lines are required. When fabricating the new lines, pay close attention to the type of fitting needed for each end. In most cases, the fittings are different for each port. Remember, the front port is for the rear brakes and the rear port is for the front brakes. Using a tubing bender, cutter and SAE flare tool (not included with the master cylinder but easily rented/borrowed/purchased from your local major auto parts store. Route the 3/16 inch diameter hard lines to connect with your existing configuration. Connect the FRONT port to your rear brakes & the REAR port to the front brakes. Once you have the tube where you need it, slide one of the supplied 3/8 x 3/16″ tube nuts on the hard line, flare with the SAE flare tool & install the fitting. If your configuration requires different fittings then use the ones from the old setup.
  5. Repeat this procedure for the other tube.
  6. You should be able to re-use your stock pushrod with this new master cylinder. If however, the stock pushrod is too short and fails to connect with the new master cylinder piston with the pedal all the way up, you will need a longer or adjustable pushrod. NOTE: You must ensure that the pushrod CANNOT fall out of the master cylinder when installed. If
    your car is not equipped with a pedal stop under the dash you will need to install one. You must limit the
    pedal from being able to move too far toward the driver and the master cylinder pushrod loosing contact with the master cylinder piston.
  7. Bleed the brakes and check over the ENTIRE installation!

Before your first outing, it is critical you check over the install. Make sure nothing interferes with other components. With someone pressing hard on the pedal inspect all the new fittings for leaks.

For Your Information

If the brake pedal is spongy even after all of the air is expelled from the system, you may want to use a master cylinder with a larger bore. On the other hand, if the pedal is rock hard, you may need a smaller bore master cylinder. Just remember, A smaller bore master cylinder yields more brake force, but also more pedal travel. Versus a larger bore master cylinder will have less pedal travel, but less brake force.

This article is the intellectual property of Simmons BOSS CREATIONS. Any reuse of the contents must include the following attribution:

Marcus Simmons, ASE Certified
Phone: (248) 461-6977