NOTE: See Paragraph 9-16 for Power Brake Cylinder Service.


Filling 1956 Buick Brake Master Cylinder

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 of the master cylinder.

On all cars (with regular or power brakes), the brake fluid reservoir is on the master cylinder which is located under the hood on the left side.

Thoroughly clean filler cap nut before removal to avoid getting dirt into reservoir. Add fluid as required to bring level to 1/2″ to 1″ below top of filler opening. Use G.M. or Delco Super No. 11 Hydraulic Brake Fluid.

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 1956 Buick hydraulic brake system.

Check for clear vent holes in filler cap nut and make sure gasket is in good condition before installing cap nut.

Bleeding 1956 Buick Brake Hydraulic System

A bleeding operation is necessary to remove air whenever it is introduced into the 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 1956 Buick brake pedal accompanied by poor braking action.

Air will be introduced into the hydraulic system if the 1956 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 1956 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 9-4.

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 Without Pressure Tank

  1. Fill master cylinder (subpar. a, above).
  2. 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 9-6.
    1956 Buick Bleeding Wheel Cylinder

    1956 Buick Bleeding Wheel Cylinder

  3. Depress brake pedal a full stroke, then allow pedal to return slowly to released position. Allowing pedal to return quickly may draw air into system. Continue operating pedal in this manner until fluid flows from bleeder tube into glass jar in a solid stream that is free of air bubbles, then close the bleeder valve securely. Remove bleeder tube and install screw in valve.
  4. Frequently check master cylinder to make sure that it contains fluid. Approximately 1/2 pint of fluid is required to bleed each wheel cylinder. Allowing reservoir to be emptied will cause air to be drawn into hydraulic system.
  5. When bleeding operation is completed at all wheel cylinders where needed, make sure that fluid level is 1/2″ to 1″ below top of master cylinder filler opening then install filler cap nut and gasket.
  6. Discard the brake fluid deposited in glass jar during bleeding operation. It is poor economy to attempt to clean fluid that has once been used.

Bleeding Wheel Cylinder with Pressure Tank

IMPORTANT: When using a pressure tank, air bubbles may form in the tank and enter the 1956 Buick brake hydraulic system. To avoid this, observe the following points when handling a pressure tank: (1) Do not shake or agitate the pressure tank after air pressure has been added or is being added. (2) Allow pressure tank to stand in one position as much as possible, and bring air hose over to tank when adding head of air. (3) Make certain the valves on the pressure tank lines are not defective allowing air to be sucked in when fluid passes through the lines. (4) Pressure tank should be kept at least % full of fluid to avoid air bubbles forming. (5) If pressure tank is full of air bubbles, release air pressure and those bubbles will increase in size and be forced to top of fluid, and escape.

  1. Thoroughly clean master cylinder filler cap nut and surrounding area, then remove cap nut.
  2. Make sure that pressure tank is at least 1/3 full of specified brake fluid, that hose and master cylinder reservoir are filled with fluid, then attach hose to master cylinder filler opening.
  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 9-6.
  4. Open pressure tank hose valve to apply fluid to master cylinder under pressure that does not exceed 35 pounds. Too much pressure may blow out the expansion plug in master cylinder. It is not necessary to pump the 1956 Buick brake pedal when using pressure tank.
  5. When fluid flows from bleeder tube into glass jar in a solid stream that is free of air bubbles, that particular cylinder and line are bled; tighten bleeder valve securely, remove bleeder tube and install screw in bleeder valve.
  6. When bleeding operation is completed at all wheel cylinders where needed, make sure that fluid level is 1/2″ to 1″ below top of master cylinder filler opening then install filler cap nut and gasket.

Flushing 1956 Buick Brake Hydraulic System

It is recommended that the entire hydraulic system be thoroughly flushed and cleaned every 15,000 miles, or whenever new parts are installed in the hydraulic system, or new shoes or linings are installed. Flushing is also recommended if there is any doubt as to the grade of fluid in the system or if fluid has been used which contains the slightest trace of mineral oil.

Flushing is performed at each wheel cylinder in turn, and in the same manner as the bleeding operation except that bleeder valve is opened 1 1/2 turns and the cleaning fluid is forced through the pipes and wheel cylinder until it emerges clear in color. Approximately one quart of cleaning fluid is required to flush the hydraulic system thoroughly.

When flushing is completed at all wheel cylinders, substitute specified brake fluid at master cylinder and repeat the operation at each wheel cylinder in turn until clear brake fluid emerges in a solid stream free of air bubbles. Make sure that all cleaning fluid is forced out of hydraulic system by the fresh brake fluid. Also, make certain that master cylinder reservoir is filled to proper level when job is completed.



The minor 1956 Buick brake adjustment is intended for use where braking action is equal and generally satisfactory except that brake pedal goes too close to toeboard due to wear of brake linings. If braking action is unequal or otherwise unsatisfactory, the major brake adjustment should be used (par. 9-10).

Do not adjust when 1956 Buick brakes are warm. Brake drums should be approximately room temperature.

Preliminary Checks

  1. Jack up all four wheels in a safe manner.
  2. Check fluid level in master cylinder reservoir and add fluid if necessary (par. 9-7).
  3. Fully release 1956 Buick parking brake lever.
  4. Pull on both ends of rear brake cable a number of times to make sure that cables operate rear brake shoes freely and do not bind in conduits. Check for free movement of cable in brake ca6le sheave and check brake cable spring for tension. If cable action is not free, the cable and sheave should be lubricated (par. 9-9). Replace a weak or broken cable spring.
  5. Check all anchor pin nuts with 16″ Wrench J 854 to make certain nuts are tight. See figure 9-9. If an anchor pin nut is found loose, reset anchor pin as instructed in paragraph 9-10, step 19 otherwise do not disturb anchor pins.
  6. Check 1956 Buick brake pedal adjustment as follows (subpar. b).

1956 Buick Brake Pedal Adjustment

NOTE: See paragraph 9-16 for power brake pedal adjustment.

No brake pedal adjustment is necessary for the direct acting master cylinder used on cars with regular brakes. However, the pedal must return freely to the fully released position with the piston guide contacting the bumper washer. If pedal does not return fully, the compensating holes in the piston will not clear the primary cup and pressure will build up in the 1956 Buick brake system. See Figure 9-7.