Written by: Mike Ervin

A bleeding operation is necessary to remove air whenever it is introduced into the hydraulic brake system.

It may be necessary to bleed the hydraulic system at all four foundation brakes if air has been introduced through low fluid level or by disconnecting brake pipes at master cylinder.  If brake pipe is disconnected at any wheel cylinder, or caliper, then that wheel cylinder or caliper only need be bled.  If pipes are disconnected at any fitting located between master cylinder and foundation brakes, then all foundation brakes served by the disconnected pipe must be bled.

Time required to bleed the hydraulic system when the master cylinder is removed 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.

Manual Bleeding
With power brakes, remove the vacuum reserve by applying brakes several times with the engine off.

1.  Fill the master cylinder reservoirs with brake fluid and keep at least one-half full of fluid during the bleeding operation.

2.  If the master cylinder is known or suspected to have air in the bore, then it must be bled before any wheel cylinder or caliper in the following manner;
 

a.  Disconnect the forward (blind end) brake pipe connection at the master cylinder.

b.  Allow brake fluid to fill the master cylinder bore until it begins to flow from the forward pipe connector port.

c.  Connect the forward brake pipe to the master cylinder and tighten.

d.  Depress the brake pedal slowly one time and hold.  Loosen the forward brake pipe 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 all air is removed from the bore.  Care must be taken to prevent brake fluid from contacting any painted surface.

e.  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.

f.  If it is known that the calipers and wheel cylinders do not contain any air, then it will not be necessary to bleed them.

3.  Individual wheel cylinder or calipers are bled only after all air is removed from the master cylinder.

a.  Place a proper size box end wrench over the bleeder valve.  Attach transparent tube over valve and allow tube to be hand 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 bleeder screw and slowly release pedal.  Wait 15 seconds.  Repeat the sequence, including the 15 second wait until all air is removed.  It may be necessary to repeat the sequence 10 or more times to remove all the air.  JB1 thru JB6 gas engine vehicle- 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.

4.  It is necessary to bleed all of the wheel cylinders and calipers, the following sequence should be followed:
1) Right rear wheel cylinder; 2) Left rear wheel cylinder;  3) Right front caliper; 4) Left front caliper.

5.  Check the brake pedal for "sponginess" and the brake warning light for indication of unbalanced pressure.  Repeat entire bleeding procedure to correct either of these two conditions.

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