S10 Pickup, Sonoma 2000-2004

Master Cylinder


If you have disconnected the brake pipes from the master cylinder, you must bleed the master cylinder.

  1. Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.
  3. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder.
  5. Reconnect the brake pipe to the master cylinder port and tighten securely.
  7. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
  9. Loosen the same brake pipe to purge air from the open port of the master cylinder.
  11. Tighten the brake pipe, then have the assistant slowly release the brake pedal.
  13. Wait 15 seconds, then repeat steps 2-6 until all air is purged from the same port of the master cylinder.
  15. With the front brake pipe installed securely to the master cylinder - after all air has been purged from the front port of the master cylinder - loosen and separate the rear brake pipe from the master cylinder, then repeat steps 2-7.
  17. After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.