MASTER CYLINDER BLEEDING
See Figure 1
This procedure can be performed with the master cylinder mounted in position on the vehicle. However, it is most commonly performed with the master cylinder mounted in a soft jawed vise.
- Attach bleeder tubes to the cylinder outlet ports and insert tubes into the reservoir compartments. The bleeder tubes may be made up from brake line equipped with the correct master cylinder end fitting.
- Fill the brake master cylinder reservoir with clean, fresh brake fluid, meeting DOT 3 or DOT 4 specifications.
- If performing this procedure off the vehicle, insert a wooden dowel into the piston end of the cylinder. Otherwise, use the brake pedal to operate the master cylinder piston.
- Push the piston inward and release it. Continue this "pumping operation'' until no air bubbles are visible in the brake fluid.
- Correct the fluid level in the master cylinder as necessary.
- Remove the bleeder lines, install the reservoir caps and install the master cylinder.
BRAKE SYSTEM BLEEDING
See Figures 2, 3 and 4
When any part of the hydraulic system has been disconnected for repair or replacement, air may get into the lines and cause spongy pedal action (because air can be compressed and brake fluid cannot). To correct this condition, it is necessary to bleed the hydraulic system to be sure all air is purged.
When bleeding the brake system, bleed one brake component at a time, beginning at the wheel cylinder or caliper with the longest hydraulic line (farthest from the master cylinder). ALWAYS Keep the master cylinder reservoir filled with brake fluid during the bleeding operation. Never use brake fluid that has been drained from the hydraulic system, no matter how clean it is.
The primary and secondary hydraulic brake systems are separate and are bled independently. During the bleeding operation, do not allow the reservoir to run dry. Keep the master cylinder reservoir filled with brake fluid.
- Clean all dirt from around the master cylinder fill cap
- Fill the brake master cylinder reservoir with clean, fresh brake fluid, meeting DOT 3 or DOT 4 specifications, until the level is within 1 / 4 in. (6mm) of the top edge of the reservoir.
- Clean the bleeder screws at all 4 wheels, in addition to any bleeder screws located at the master cylinder or combination valve. The bleeder screws are located on the back of the brake support plate (drum brakes) and on the top of the brake calipers (disc brakes).
- Attach a length of rubber hose over the bleeder screw and place the other end of the hose in a glass jar, submerged in brake fluid.
- Open the bleeder screw 1 / 2 - 3 / 4 turn. Have an assistant slowly depress the brake pedal.
- Close the bleeder screw and tell your assistant to allow the brake pedal to return slowly. Continue this process to purge all air from the system.
Do not pump the brake pedal during the bleeding procedure.
- When bubbles cease to appear at the end of the bleeder hose, close the bleeder screw and remove the hose. Tighten the bleeder screw to 61-87 inch lbs. (7-9 Nm).
- Check the master cylinder fluid level and add fluid accordingly. Do this after bleeding each wheel.
- Repeat the bleeding operation at the remaining 3 wheels, ending with the one closet to the master cylinder.
- Refill the brake master cylinder reservoir with clean, fresh brake fluid, meeting DOT 3 or DOT 4 specifications.