How to Bleed ABS Brakes in a 1999 GMC Truck

Since 1918, GMC has produced full-sized pickup trucks. In 1982, GMC began defending American soil against the influx of compact foreign pickups by releasing the S-15 compact pickup -- alongside the Chevy S-10. In 1992, GMC changed the S-15's name to the Sonoma. In the 1999 model year, GMC offered three lines of pickups: Sonoma, Sierra and Sierra Classic. All three pickups had anti-lock brakes as an available option and bleeding this brake system requires a very specific series of steps. Failure to follow each step precisely could lead to a malfunction in the brake system.

Instructions

1

Remove the lid from the master cylinder reservoir and add DOT 3 brake fluid until it reaches the "Max" line on the reservoir. Press the master cylinder reservoir lid back onto the reservoir.

2

Raise the front of the truck with a floor jack, and position jack stand beneath the frame rails. Lower the GMC onto the jack stands. Raise the rear of the GMC with a floor jack and slide jack stands under the frame rails. Lower the rear of the truck onto the jack stands.

3

Crawl beneath the truck, just behind the right-rear (passenger side) wheel and locate the bleeder valve -- a 1/4-inch metal valve -- on the rear of the brake caliper of the drum backing plate.

4

Press a 1/4-inch rubber hose onto the end of the bleeder valve. Place the other end of the hose into a clean, clear container. Fill the container with DOT 3 brake fluid until the fluid submerges the end of the hose.

5

Turn the bleeder valve a half- to full-turn, using a combination wrench. Instruct your assistant to press the brake pedal slowly until it reaches the floor. Watch the end of the hose and look for bubbles coming from the end of the hose. Close the bleeder valve, using a combination wrench, and instruct your assistant to release the brake pedal.

6

Wait 15 seconds and repeat Step 6 until no bubbles come from the hose. Refill the master cylinder with fresh DOT 3 fluid after every four to six pushes of the brake pedal to prevent running it out of fluid.

7

Repeat Steps 3 through 6 on the three remaining wheels in the following order: left rear, right front and left front.

8

Plug a diagnostic scanner with functions test capabilities into the diagnostic link connector under the driver's side of the dashboard.

9

Turn the GMC's ignition to the "Run" position, but do not start the truck. Turn the scanner on and follow its on-screen instructions to initiate the anti-lock brake system function test -- this process varies with every scanner. Press and hold the brake pedal until the ABS function test completes. Release the brake pedal once the test completes. Turn the ignition to the "Off" position. Repeat this step three times. This releases any trapped air in the ABS pump.

10

Repeat Steps 3 through 9 until no air bubbles appear from the end of the rubber hose during the bleeding process. This is required, as Step 9 releases air that was once trapped in the ABS pump, and it may now be in the lines.

11

Raise the rear of the truck off the jack stands, using a floor jack, and remove the jack stands. Lower the rear of the truck to the ground. Raise the front of the truck off the stands, using a floor jack. Pull the stands from under the front of the truck and lower the GMC to the ground.

12

Check the fluid in the master cylinder reservoir and add fresh DOT 3 fluid until it is between the "Min" and "Max" lines on the reservoir.