It is necessary to bleed the brake system any time air is introduced into the hydraulic system.
It may be necessary to bleed the hydraulic system at all four brakes positions, and/or the master cylinder, if air has been introduced through low fluid level or by disconnecting the brake lines at the master cylinder. If a brake line is disconnected at any wheel, then that wheel caliper only need be bled. If lines are disconnected at any fitting located between the master cylinder and brakes, then the brake system served by the disconnected line must be bled.
The time required to bleed the hydraulic system can be reduced if the master cylinder is filled with fluid and as much air as possible is expelled before the cylinder is installed on the vehicle. Power brakes require removing the vacuum reserve by applying the brakes several times with the engine off.
- Fill the master cylinder reservoirs with brake fluid and keep them at least half full of fluid during the bleeding operation.
- If the master cylinder is known or suspected to have air in the bore, then it must be bled before any caliper in the following matter.
- Disconnect the forward brake line connection at the master cylinder.
- Fill the master cylinder bore until fluid begins to flow from the forward line connector port.
- Connect the forward brake line to the master cylinder and tighten it.
- Have an assistant depress the brake pedal slowly one time and hold it down. Loosen the forward brake line connection at the master cylinder to purge air from the bore. Tighten the connection and then release the brake pedal slowly. Wait 15 seconds. Repeat the sequence including the 15 second wait, until air is removed from the bore. Use care as brake fluid dissolves paint.
- After all air has been removed at the forward connection, bleed the master cylinder at the rear (cowl) connection in the same manner as the front in step d, above.
- If it is known that the calipers do not contain any air, then it will not be necessary to bleed them. But to be on the safe side, bleed the front and rear calipers.
- Individual calipers are bled only after all air is removed from the master cylinder.
- Place a proper size box end wrench over the bleeder valve.
- Attach a transparent tube over the valve and allow the tube to hang submerged in brake fluid in a transparent container.
- Depress the brake pedal slowly one time and hold.
- Loosen the bleeder valve to purge the air from the cylinder.
- Tighten the bleeder screw and slowly release the pedal.
- Wait 15 seconds and repeat the above sequence including the 15 second wait until all air is removed.
It may be necessary to repeat the sequence 10 or more times until all air is removed from the system. Rapid pumping of the brake pedal pushes the master cylinder secondary piston down the bore in a manner that makes it difficult to bleed the rear side of the system.
- If it is necessary to bleed all of the calipers, the following sequence should be followed: right rear; left rear; right front; left front (furthest from master cylinder to closest).
Check the brake pedal for sponginess and the brake warning light for indication of unbalanced pressure. To correct either of these two conditions repeat the entire bleeding procedure.
Pressure bleeding equipment must be the diaphragm type and must have a rubber diaphragm between the air supply and the brake fluid to prevent air, moisture and other contaminants from entering the hydraulic system.
- Install the bleeder adapter J-29567 to the master cylinder reservoir.
- Charge the bleeder tool J-29532 to 20-25 psi (140-172 kPa).
- Connect the line to the adapter. Open the line valve and depress the bleed-off valve on top of the adapter until a few drops of fluid appears.
- Raise the vehicle and support with jackstands. Remove the wheel assemblies at the axle being bled.
- Bleed the brakes in the following sequence: right rear, left rear, right front and left front. Attach a clear tube over the bleeder screw. Using the proper size box wrench, open the bleeder screw and bleed until no air is seen in the fluid.
- Close the bleeder screw and repeat step 5 for each caliper being bled.
- Install the wheel assemblies and torque the lug nuts to 100 ft. lbs. (136 Nm). Lower the vehicle and check for a spongy brake pedal or if the brake warning light is on. If these problems occur, repeat the bleeding procedure until the brake pedal is firm at all times when the engine is not running.
- Remove the brake bleeding equipment and fill the reservoir to the FULL level. Clean the reservoir cap and diaphragm with a clean towel and reinstall.