GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 Achieva 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Master Cylinder Overhaul

Disassembly Procedure

    Object Number: 165371 Size: MH

    Important: The master cylinder reservoir cover and reservoir diaphragm may be inspected and/or serviced without removing the master cylinder from the vehicle.

  1. Remove the master cylinder from the vehicle. Refer to Master Cylinder Replacement .
  2. Clean the master cylinder reservoir cover.
  3. Remove the master cylinder reservoir cover (1).
  4. Remove the master cylinder reservoir diaphragm (2).
  5. Empty the fluid from the reservoir if the master cylinder is to be completely removed and overhauled.
  6. Inspect the master cylinder cover and the diaphragm for the following conditions. Replace the parts as necessary:
    7. • Cuts
    • Cracks
    • Nicks
    • Deformation

    Object Number: 165377 Size: SH
  7. Remove the fluid level switch (1).

    8. Object Number: 165371 Size: MH
  8. Remove the proportioner valve assemblies (15-19).
  9. Remove the piston retainer (12) while depressing the primary piston. Use care not to damage the primary piston (11), the master cylinder bore, or the piston retainer groove.
  10. Remove the primary piston. Apply low pressure, non-lubricated, compressed air into the upper outlet port at the blind end of the bore with all of the other outlet ports plugged.
  11. Remove the secondary piston (9). Apply low pressure, non-lubricated, compressed air into the upper outlet port at the blind end of the bore with all other outlet ports plugged.
  12. Remove the secondary piston spring (6) and the spring retainer (7). Apply low pressure, non-lubricated, compressed air into the upper outlet port at the blind end of the bore with all of the other outlet ports plugged.
  13. Remove the secondary seal (10).
  14. Remove the primary seal (8).
  15. Remove the spring retainer from the secondary piston.
    16. • Clean all parts in clean, denatured alcohol.
    • Dry the parts with non-lubricated, compressed air.
    • Do not use an abrasive on the bore.
  16. Inspect the master cylinder bore for scoring or corrosion. Replace the master cylinder if damage is found.

Assembly Procedure

    Object Number: 165371 Size: MH
  1. Lubricate all rubber parts with clean brake fluid in order to ease assembly.
  2. Install the lubricated secondary seal (10) onto the secondary piston (9).
  3. Install the lubricated primary seal (8) onto the primary piston (11).
  4. Install the spring retainer (7) onto the secondary piston.
  5. Install the lubricated secondary piston spring (6) into the cylinder bore.
  6. Install the lubricated secondary piston assembly into the cylinder bore.
  7. Install the lubricated primary piston into the cylinder bore.
  8. Depress the primary piston in order to install the piston retainer (12).
  9. Install the proportioner valve assemblies (15-19). Refer to Proportioning Valve Replacement
  10. Install the fluid level switch.
  11. Install the master cylinder reservoir diaphragm (2) into the reservoir cover (1).
  12. Install the master cylinder reservoir cover onto the master cylinder reservoir.
  13. Install the master cylinder.