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TM 103930-671-24
Optional Procedure
Manual Brake Bleeding
1
When bleeding the brakes manually, it is
recommended to install temporary bleed drain
lines on the bleeder screws. Use an adequate
length of flexible tubing (e.g. clear plastic)
having an inside diameter to fit tightly over the
bleeder screw opening to prevent air from
entering. This allows bleeding to be done quickly
and cleanly.
NOTE
If drain lines are not used, the bleeder
screw must be altematively opened and
closed in sequence while bleeding the
system,
as
described
in
Manual
Bleeding Procedure below.
2.
Install bleed drain on each bleeder screw. Fit
the drain tube only over the outer end of the
bleeder screw, leaving wrench clearance at the
bottom.
3.
Immerse the open end of each drain line in a jar
partially filled with clean hydraulic brake fluid.
Put the jar in a position above the level of the
bleeder screws and where you can watch for air
bubbles in the fluid.
4.
When moving the brake pedal, be sure that the
open end of the bleed drain lines are always
immersed in the jar of clean fluid to prevent air
from reentering the system. Watch for air
bubbles escaping from the bleed lines.
Manual Bleeding Method -
Service Brake Circuit
Alternate method if pressure bleeder is not available.
NOTE
When bleed drain lines are not installed
(see Optional Procedures) the bleeder
screws must be opened during brake
pedal downward movement, and closed
before and during brake pedal upward
return movement, to prevent air from
entering the system during pedal return
stroke.
1.
Open the bleeder screw of the brake circuit
being bled.
2.
Push (stroke) the brake pedal fully down slowly
several times (5-10 times minimum).
3.
Check and refill brake fluid reservoir with
recommended hydraulic brake fluid. Keep
reservoir filled during bleeding.
4.
When the bleeding fluid appears to be free of air
bubbles, tighten the bleeder screw and test the
brake pedal action.
5.
Push on the brake pedal and hold in the fully-
down position. Check for a feeling of solid
resistance when the brake pedal stops. The
pedal must feel firm and not move down farther
after it stops.
6.
If the brake pedal motion or feel is not correct:
a)
First, push the pedal fully down several
times, with the bleeder screws closed.
This will give movement to the brake fluid
and wheel cylinder pistons to aid in
dislodging
any
remaining
entrapped
bubbles of air. Wait several minutes.
b)
Then, repeat the bleeding procedure, as
previously described.
c)
Test the brake pedal action.
7.
If necessary, bleed the inching circuit.
F-398
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