The Rear Brakes on My 1991 Chevy Pickup Won't Bleed & Just Air Comes Out

Brake problems on any vehicle poses a major safety issue. When brakes have air trapped in the line, the brakes fail to properly engage, thus diminishing your stopping power. If no fluid is in the line, you lose all stopping power. The 1991 Chevrolet truck series uses a master cylinder and brake booster to supply additional power to the brakes. Bleeding the brakes frees trapped air from the line. Sometimes extensive amounts of air are trapped, making it appear as though no fluid is in the line.

Instructions

1

Raise the rear of the vehicle one wheel at a time. Place jack stands under each wheel at the axle as you raise the wheel. Remove the lug nuts with a lug wrench and remove the tires. Place them to the side.

2

Visually inspect the brake lines coming from both rear brakes. Trace these back to the engine while looking for signs of leaks or breaks in the line. Make sure to check the drums also for signs of leaks. You will need to carefully pull off the drum and inspect the caliper for signs of leaking. You should see no signs of fluid within the drum cylinder. Replace the drum onto the drum cylinder. If no breaks in the line or leaks are identified, remove the top off of the brake fluid reservoir and fill to the full line.

3

Loosen the bleed screw on the passenger rear tire first. When bleeding brakes, always start from the brake farthest from the reservoir to make sure trapped air does not leak back into the system. Place the rubber tubing onto the bleed screw and into the clear plastic bottle. Make sure the bottle has a small amount of brake fluid in the bottom and the end of the rubber tubing is immersed in the fluid.

4

Check for vacuum pressure on the line. Have an assistant depress the brake pedal and hold it in place. Loosen the bleed screw fully so that the air can escape. You should see bubbles come out the end of the tubing. Have the assistant release the brake pedal. If a vacuum exists, which is necessary for proper operation, the tubing will suck fluid out of the bottle. If that is the case, then you just have extensive amounts of air trapped in the line.

5

Close the bleed screw and build up pressure in the brake lines. Have your assistant firmly press the brake pedal down three to five times. On the last time, have him hold it down while you loosen the bleed screw. If no air was coming out previously and no vacuum was identified, you have a clogged bleed screw. Increasing the pressure in this manner will force any blockage out. Make sure you have vacuum in the line after clearing out obstructions by repeating step four.

6

Bleed the passenger rear tire. Have the assistant press the brake pedal to the floor and hold it there. Loosen the screw and allow the air to escape. Once the bubbles stop, tighten the screw and have the assistant release the pedal. Repeat the process until no air is coming out of the line. Tighten the bleed screw firmly. The process may take an extensive amount of time if a lot of air is present. Monitor the fluid reservoir and refill it as necessary. Do not let the reservoir get less than half full.

7

Bleed the remaining brakes (repeat step 6) starting with the driver rear, then the passenger front and then the driver front. When you have completed the rear tires, replace the wheels and lug nuts and lower them to the ground. Raise the front wheels and remove those wheels in the same fashion. Once complete, install the wheels and lower the vehicle to the ground. Test the brakes.