SORRY, PAGE UNDER CONSTRUTION

Master Cylinder Push Rod (and Stoplight switch) Adjustment

Proper adjustment of the master cylinder push rod and brake pedal free play is very important. Incorrect adjustment could position master cylinder pistons over compensating ports which would not allow full hydraulic pressure release resulting in excessive brake drag.

The adjustment should be done in accordance with the following procedure. The same procedure also applies to stop lamp switch adjustment.

  1. Disconnect the stop lamp switch electrical lead. Loosen the lock nut and position switch away from pedal blade.
  2. Remove "push rod end" lock nut, push rod end bolt and pedal return spring bracket assembly.
  3. Position a ".010-.015" spacer between pedal blade and pedal stop (Fig. 1).
  4. Turn "push rod end" in or out until end bolt can be inserted into pedal blade and rod end freely.
  5. Install spring assembly, install and torque end bolt nut to 30 foot pounds and lock nut to 120 inch pounds, remove spacer.
  6. Readjust stop lamp switch by advancing switch until plunger contacts pedal blade, continue adjustment 2-1/2 complete turns. Tighten lock nut, check stop lamp function.



Figure 1

Master Cylinder Internal Leak Check

The following leak test will aid in determining if a brake master cylinder is defective and should be performed before replacement or overhaul.

  1. Clean the master cylinder around the brake tubes attachment area.
  2. Disconnect front and rear brake tubes from the master cylinder ports.
  3. Cap each tube to prevent contaminents from entering the system.
  4. Connect two line pressure gauges, one to each port, on the master cylinder. Use short, approximately 6 inch length, connecting tubes. Use gauges with approximately 1,000 psi maximum capacity.

    CAUTION:
    Gauge connections must be tight with NO leakage.

  5. Pressure bleed the tubes at the gauges.
  6. Exhaust any vacuum reserve on power braked vehicles by depressing brake pedal several times.
  7. Apply and hold 500 psi for at least one 1 minute. lf additional pedal travel occurs after obtaining the 500 psi, during the one (1) minute check, the master cylinder should be considered defective and should be replaced.
  8. lf no pressure drop occurs, repeat step 7 at lower pressure of approximately fifty (50) psi.

    NOTE:
    It is important to determine if pedal travel occurs while holding a constant pressure. Care must be exercised in holding the constant pressure. If necessary, rather than apply the force with muscular effort, a prop between the seat and brake pedal could be used to generate the 500 psi. lf the pressure drops at all during a one minute period, then the master cylinder should be replaced.
  9. If the master cylinder checks good, remove the gauges and tubes.
  10. Re-connect the front and rear brake tubes. Pressure bleed at the master cylinder tube connectors.