Bleeding the brake system is required anytime the normally closed system has been opened to the atmosphere. When bleeding the system, keep the brake fluid level in the master cylinder reservoir above 1 / 2 full. If the reservoir is empty, air will be pushed through the system. If equipped with ABS, refer to theABS portion of Brakes for bleeding procedure.
If using a pressure bleeder, follow the instructions furnished with the unit and choose the correct adapter for the application. Do not substitute an adapter that "almost fits" as it will not work and could be dangerous.Master Cylinder
See Figures 1 and 2
Due to the location of the fluid reservoir, bench bleeding of the master cylinder is not recommended. The master cylinder is to be bled while mounted on the brake booster. If the fluid reservoir runs dry, bleeding of the entire system will be necessary. Two people will be required to bleed the brake system.
- Fill the brake fluid reservoir with clean brake fluid.
- For 1990-94 vehicles, disconnect the brake tube from the master cylinder.
- Have a helper slowly depress the brake pedal. Once depressed, hold it in that position. Brake fluid will be expelled from the master cylinder.
- While the pedal is held down, use a finger to close the outlet port of the master cylinder. While the port is closed, have the helper release the brake pedal.
- Repeat this procedure 3 or 4 times, until all air is bled from the master cylinder. Check the brake fluid in the reservoir every 4-5 times, making sure the reservoir does not run dry. Add clean DOT 3 brake fluid to the reservoir as needed. All air is bled from the master cylinder when the fluid expelled from the port is free of bubbles.
- Connect the brake tube to the port on the master cylinder. Add clean fluid to fill the reservoir to the appropriate level.
See Figures 3, 4, 5, 6, 7, 8 and 9
- Fill the master cylinder with fresh brake fluid. Check the level often during this procedure. Raise and safely support the vehicle.
- Starting with the wheel farthest from the master cylinder (passenger side rear wheel), remove the protective cap from the bleeder and place where it will not be lost. Clean the bleeder screw.
- Have an assistant start the engine and run at idle.
- If the system is empty, the most efficient way to get fluid down to the wheel is to loosen the bleeder about 1 / 2 - 3 / 4 turn, place a finger firmly over the bleeder and have a helper pump the brakes slowly until fluid comes out the bleeder. Once fluid is at the bleeder, close it before the pedal is released inside the vehicle.
If the pedal is pumped rapidly, the fluid will churn and create small air bubbles, which are almost impossible to remove from the system. These air bubbles will accumulate and a spongy pedal will result.
- Once fluid has been pumped to the caliper, open the bleed screw again, have the helper press the brake pedal to the floor, lock the bleeder and have the helper slowly release the pedal. Wait 15 seconds and repeat the procedure (including the 15 second wait) until no more air comes out of the bleeder upon application of the brake pedal. Remember to close the bleeder before the pedal is released inside the vehicle each time the bleeder is opened. If not, air will be introduced into the system.
- If a helper is not available, connect a small hose to the bleeder, place the end in a container of brake fluid and proceed to pump the pedal from inside the vehicle until no more air comes out the bleeder. The hose will prevent air from entering the system.
Repeat the procedure on the remaining calipers/wheel cylinders in the following order:
- Left front caliper
- Left rear caliper/wheel cylinder
- Right front caliper
- Hydraulic brake systems must be totally flushed if the fluid becomes contaminated with water, dirt or other corrosive chemicals. To flush, bleed the entire system until all fluid has been replaced with the correct type of new fluid.
- Install the bleeder cap on the bleeder to keep dirt out. Always road test the vehicle after brake work of any kind is done.