GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Bleeding the RWAL Brake System


On RWAL systems through 1992 the brake system may be bled in the usual manner with no special procedures. On 1993 vehicles a few steps (listed below) should be added to the bleeding sequence in order to ease the procedure and assure all air is removed from the system. If you have access to the additional tools required, you may use these extra steps on all RWAL vehicles to assure proper bleeding.

The use of a power bleeder is recommended, but the system may also be bled manually. If a power bleeder is used, it must be of the diaphragm type and provide isolation of the fluid from air and moisture.

Do not pump the pedal rapidly when bleeding; this can make the circuits very difficult to bleed. Instead, press the brake pedal slowly 1 time and hold it down while bleeding takes place. Tighten the bleeder screw, release the pedal and wait 15 seconds before repeating the sequence. Because of the length of the brake lines and other factors, it may take 10 or more repetitions of the sequence to bleed each line properly. When necessary to bleed all 4 wheels, the correct order is right rear, left rear, right front and left front.

Do not move the vehicle until a firm brake pedal is achieved. Failure to properly bleed the system may cause impaired braking and the possibility of injury and/or property damage

On all 1993 RWAL vehicles, or earlier vehicles if desired, use the bleeding procedure found earlier in this section, with the following additions:

  1. Make sure the ignition is in the OFF position to prevent setting false trouble codes.
  3. After properly bleeding the master cylinder, install J-39177 or an equivalent combination valve depressor tool to the combination valve. This tool is used to hold the internal valve open allowing the entire system to be completely bled.

This tool is relatively inexpensive and should be available from various aftermarket companies. Although a homemade tool may suffice, DO NOT attempt to fabricate a homemade tool unless you are CERTAIN it will not damage the valve by over-extension.

  1. Recheck the master cylinder fluid level and add, as necessary.
  3. Bleed the wheel cylinders as described earlier in this section.
  5. Attach the Tech 1® or an equivalent scan tool, then perform 3 RWAL function tests.
  7. Re-bleed the rear wheel cylinders.
  9. Check for a firm brake pedal, if necessary repeat the entire bleeding procedure.
  11. Once you are finished, be sure to remove the combination valve depressor tool.