Attach a short length of a rubber hose to the
wheel cylinder bleeder screw and allow the other
end of the hose to be submerged in a jar halfway
filled with brake fluid (fig. 7-37).
Have an assistant push on the brake pedal to
apply pressure on the brake system. It may be
necessary to pump the brake six to seven times to
build up pressure in the system.
Open the bleeder screw while watching for air
bubbles in the fluid located in the jar.
Close the bleeder screw and tell your assistant to
release the brake pedal. Repeat this procedure
until no air bubbles come out of the hose.
Bleed one wheel cylinder at a time. Do the one
farthest away from the master cylinder first and work
your way to the closest. This ensures that all the air
possible can be removed at the first bleeding operation.
Pressure bleeding of a brake system is preferred to
the method just described but requires equipment of
the type shown in figure 7-38. Pressure bleeding a
brake system is done using air pressure trapped inside a
metal air tank (bleeder ball). Pressure bleeding is quick
and easy because of the following:
It does not require an assistant.
It maintains a constant pressure in the system.
It keeps the master cylinder full during bleeding
To pressure bleed the system, proceed as follows:
Figure 7-37.Manual bleeding brake lines: (1) Bleeder
screw: (2) Bleeder hose.
Figure 7-38.Pressure bleeding a brake system.
Pour enough brake fluid in the bleeder ball to
reach the prescribed level. Charge the ball with
10 to 15 psi of air pressure.
Fill the master cylinder with brake fluid. Install
the adapter and hose on the master cylinder.
Open the valve on the hose.
A special pressure-bleeding adapter is
required on master cylinders using a
PLASTIC RESERVOIR. Use an adapter that
seals over the ports in the bottom of the master
cylinder. This will avoid possible reservoir
Attach a bleeder hose to the farthest wheel
cylinder bleed screw. Submerge the free end of
the hose in a glass container halfway filled with
Loosen the bleed screw. When fluid coming
from the submerged end of the hose is free of air
bubbles, close off the bleed screw and remove
the bleeder hose. Repeat bleeding operation on
the other wheel cylinders in proper order.
When the bleeding operation is completed, close
the valve at the bleeder ball hose and disconnect the
bleeder from the master cylinder. Check the brake fluid
level in the reservoir, ensuring it is within 1/4 inch
from the top and install the master cylinder cover.
REVIEW 1 QUESTIONS
The time frame between the instant the operator
decides to apply the brakes and the moment the
brake system is activated is known by what term?