The master cylinder must be kept properly filled to insure adequate reserve and prevent air from entering the hydraulic system. It must not be overfilled, however, as expansion due to heat absorbed at brakes and from engine would cause fluid to overflow through the vent in filler cap nut. The overflow fluid would accumulate road dust and grit which increases the possibility of foreign material getting into the hydraulic system. Dirt accumulated over the vent holes would affect operation if the master cylinder.

  1. Thoroughly clean adjacent area then remove master cylinder filler cap nut and gasket.
  2. Fill reservoir as required to bring fluid level to 1/2″ to 1″ below top of filler opening. Master Cylinder Filler J 713 with Adapter J 713-2 will automatically fill reservoir to correct level. See figure 8-5.
    1952 Buick Master Cylinder Filler and Adapter

    1952 Buick Master Cylinder Filler and Adapter

  3. Use only new G.M. or Delco Super No. 11 hydraulic fluid, or No. 12 if No. 11 is not available.
    CAUTION: Do not use shock absorber fluid or any other fluid which contains mineral oil. Do not use a container which has been used for mineral oil. Even a trace of mineral oil will cause swelling and distortion of rubber parts in the 1952 Buick hydraulic brake system.
  4. Check for clear vent holes in filler cap nut, then install cap nut and gasket.



A bleeding operation is necessary to remove air whenever it is introduced into the 1952 Buick hydraulic brake system. Since air is compressible and hydraulic fluid is not, the pressure of air in the system is indicated by a springy, spongy feeling on the brake pedal accompanied by poor braking action.

Air will be introduced into the hydraulic system if the 1952 Buick brake pedal is operated when the fluid is too low in master cylinder reservoir. Air will also enter the system whenever any part of hydraulic system is disconnected.

It will be necessary to bleed the hydraulic system at all four wheel cylinders if air has been introduced through low fluid level or by disconnecting brake pipe at master cylinder. If 1952 Buick brake pipe is disconnected at any wheel cylinder, then that wheel cylinder only need be bled. If pipes are disconnected at any fitting located between master cylinder and wheel cylinders, then all wheel cylinders served by the disconnected pipe must be bled. See figure 8-3.

Sequence for Bleeding Wheel Cylinders

It is advisable to bleed one wheel cylinder at a time to avoid getting fluid level in reservoir dangerously low. The correct sequence of bleeding is left front, right front, left rear, right rear. This sequence expels air from the lines and wheel cylinders nearest to the master cylinder first, and eliminates the possibility that air in a line close to the master cylinder may enter a line farther away after it has been bled.

CAUTION: Do not perform bleeding operation while any brake drum is removed.

Bleeding Wheel Cylinder with Master Cylinder Filler J 71 3

  1. Thoroughly clean master cylinder filler cap nut and surrounding area, then remove cap nut.
  2. Fill Master Cylinder Filler J 713 with specified brake fluid (par. 8-8) and use Adapter J 713-2 to support the filler in place on master cylinder. See figure 8-5. Leave Filler J 713 in place during all bleeding operations as it automatically maintains the proper level in reservoir as fluid is pumped out of master cylinder.
  3. Remove screw and attach Brake Bleeder Tube J 628-A to wheel cylinder bleeder valve. Place lower end of bleeder tube in a clean glass jar. Unscrew bleeder valve 3/4 of a turn, using Bleeder Wrench J 627. See figure 8-6.