How to Bleed the ABS Braking System on a 1989 Silveradoby Tim Petruccio
The 1989 Chevrolet C/K 1500 was equipped with rear wheel antilock brakes, commonly known as RWAL. The antilock brake system or ABS require a primary and secondary bleeding to remove all air from the system. The system combines the ABS module with the primary brake system and also includes a combination valve and an isolation-dump valve. All of these components must be bled on the 1989 C/K 1500 RWAL system. Bleeding the brakes will create stronger stopping power by expelling air that weakens it from the system. The RWAL system should be bled any time a line is removed or after replacing any brake line components.
Park the Chevrolet on a completely level driveway or surface. Open the hood of the 1500. Check the level in the brake fluid reservoir and fill it to the "Full" mark on the side, if needed. Install the fluid reservoir lid and diaphragm back onto the reservoir, and lock it when you are finished filling.
Locate the combination valve below the master cylinder and reservoir. The combination valve only has one wire going to it. Do not confuse this with the dump valve, which has four wires. Locate the pin on the top of the combination valve. Install locking pliers or tape around the combination valve to hold the pin down for the entire bleeding process.
Loosen the front wheel lug nuts with a tire iron. Raise the front of the truck with a jack. Place jack stands beneath the front frame rails, just inward from the lower control arms. Lower the truck onto the stands. Remove the front lug nuts, then remove the front wheels from the truck.
Loosen the rear wheel lug nuts with a tire iron. Raise the rear of the truck with a jack. Place jack stands beneath the rear axle housing, about 6 inches inward from the rear tires. Lower the truck onto the stands. Remove the rear lug nuts completely, then remove the rear wheels from the truck.
Spray all four bleeder screws on the front and rear brakes with aerosol rust penetrating spray. Spray the bleeders inward on the front calipers so you do not accidentally get the penetrating spray on any of your front brake components. Allow the penetrating spray to set on the bleeder screws for at least 10 to 15 minutes. Ask an assistant to sit in the driver's seat of the truck carefully after the penetrating spray has set.
Instruct your assistant to depress the brake pedal as far as it will go downward and hold it. Place a drip pan beneath the passenger rear brake assembly. Open the bleeder screw on the passenger rear brake assembly with an open-end wrench. Allow the combination of brake fluid and air to leave the system and enter the drip pan. Close the bleeder screw and instruct your assistant to release the brake pedal. Repeat this step three times on the passenger rear of the truck.
Repeat Step 6 on the driver's rear brake assembly. Check the brake fluid reservoir under the hood, and fill the reservoir if needed. Install the reservoir lid and diaphragm and lock it, when filling is completed.
Instruct your assistant to depress the brake pedal as far down as it will go and hold it. Place your drip pan beneath the passenger front caliper. Open the bleeder screw on the caliper with an open-end wrench and allow the combination of brake fluid and air to escape. Close the bleeder screw and instruct your assistant to release the brake pedal. Repeat this step three times on the passenger side of the truck.
Repeat Step 8 to complete the primary bleeding on the driver's front caliper. Check the brake fluid reservoir, and fill it if needed. Install and lock the reservoir lid and diaphragm when filling is completed.
Place your drain pan beneath the passenger rear brake assembly. Instruct your assistant to pump the brake pedal five to 10 times, or until the brake pedal becomes stiff and hard to depress. Tell your assistant to hold the weight of his foot on the pedal and follow the pedal to the floor of the truck. Open the passenger rear bleeder screw. Close the bleeder screw when the pressure from the line is released. Repeat this step until only brake fluid comes out of the rear bleeder, rather than air and fluid mixed.
Repeat Step 10 on the driver's rear, followed by the passenger front, then the driver's front of the truck, to complete the bleeding process. Check your brake fluid reservoir when you are moving from the rear to the front of the truck, and fill it if needed. Install the lid and diaphragm when filling is done, and lock the reservoir lid in place. Instruct your assistant to exit the vehicle carefully. Remove the locking pliers or tape from the combination valve pin.
Install all four wheels onto the truck and tighten the lug nuts snug using a tire iron. Raise the rear of the truck off of the jack stands, then remove the jack stands from beneath the truck. Lower the truck to the ground. Raise the front of the truck off of the jack stands, then remove the stands from beneath the truck. Lower the front of the truck to the ground. Tighten all four wheel lug nuts in a "star" pattern to 120 foot-pounds of torque, with a 1/2-inch-drive torque wrench and wheel nut socket.
Instruct your assistant to sit back in the driver's seat of the truck. Place a cup or empty butter container beneath the isolation-dump valve, which has four wires connected to it at the wiring harness. Instruct your assistant to pump the brake pedal until the pedal is stiff and to hold his foot on the pedal and follow it to the floor. Open the bleeder screw on the bottom of the isolation-dump valve to release air from the valve. Close the bleeder when pressure has been released, and tell your assistant to release the brake pedal.
Repeat the bleeding process in Step 13 until only brake fluid exits the isolation-dump valve. Check and fill the fluid reservoir. Install and lock the reservoir lid when you are finished filling.
- When all of the air has left the system and the bleeder screws are pushing out only brake fluid, you will notice there is no hissing noise when you open the bleeder. If there is a hissing noise, there is still air in the system.
- Never raise a vehicle on uneven ground or a slope. This can cause jacks or jack stands to collapse suddenly.
Items you will need
- Tire iron
- 2-ton or greater capacity floor jack
- 4 jack stands
- 1 can PB Blaster, Liquid Wrench, Freeze-Off or similar penetrating spray
- Open-end wrench set
- 1 gallon or larger drip pan
- 1 cup or empty butter container
- Assistant or second person
- Locking pliers or electrical tape
- 1-pint DOT 3 or higher brake fluid