GM Full Size Vans 1967-1986 Repair Guide

Bleeding the Brakes



See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: Attach the hose and bottle to the bleeder screw, then loosen it with a flare nut wrench

Click image to see an enlarged view

Fig. Fig. 2: Have an assistant pump, then hold in the brake pedal while you bleed each wheel

The brake system must be bled when any brake line is disconnected or there is air in the system.

Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded.

Never bleed a wheel cylinder when a drum is removed.

  1. Clean the master cylinder of excess dirt and remove the cylinder cover and the diaphragm.
  3. Fill the master cylinder to the proper level. Check the fluid level periodically during the bleeding process, and replenish it as necessary. Do not allow the master cylinder to run dry, or you will have to start over.
  5. Before opening any of the bleeder screws, you may want to give each one a shot of penetrating solvent. This reduces the possibility of breakage when they are unscrewed.
  7. Attach a length of vinyl hose to the bleeder screw of the brake to be bled. Insert the other end of the hose into a clear jar half full of brake fluid, so that the end of the hose is beneath the level of fluid. The correct sequence for bleeding is to work from the brake farthest from the master cylinder to the one closest; right rear, left rear, right front, left front.
  9. The combination valve (all vehicles with disc brakes) must be held open during the bleeding process. A clip, tape, or other similar tool (or an assistant) will hold the metering pin in.
  11. With power brakes, depress and release the brake pedal three or four times to exhaust any residual vacuum.
  13. Have an assistant push down on the brake pedal. Open the bleeder valve slightly. As the pedal reaches the end of its travel, close the bleeder screw. Repeat this process until no air bubbles are visible in the expelled fluid.

Make sure your assistant presses the brake pedal to the floor slowly. Pressing too fast will cause air bubbles to form in the fluid.

  1. Repeat this procedure at each of the brakes. Remember to check the master cylinder level occasionally. Use only fresh fluid to refill the master cylinder, not the stuff bled from the system.
  3. When the bleed process is complete, refill the master cylinder, install its cover and diaphragm, and discard the fluid bled from the brake system.