Relieve drag on drum by rotating shaft
in opposite direction. Then rotate
shaft one complete turn (two complete
turns with a new lining) to provide
correct lining clearance.
Adjust both shoes in each brake to as
near same Iining-to-drum clearance
b. Bleeding of Hydraulic Brake System.
The semitrailer brake system must be con-
nected to the brake system of the towing
since the brake pedal must be pressed and
released to actuate the system. The master
cylinder reservoir must be kept full during
bleeding operations or air will enter the
system and make rebleeding necessary.
of brake dust shield enclosure.
Place an end of a length of rubber tubing
over the bleeder screw. Submerge the free
end of the tube in a bottle or jar partially
(All models except M127)
Remove vent tube assembly and filler cap
from top of reservoir of hydraulic master
cylinder (fig. 4-38). Fill reservoir with hy-
draulic brake fluid to within one-half inch
While brake pedal on towing vehicle is being
pumped slowly up and down, open bleeder
screw three-quarter turn clockwise. Liquid
will be forced through line to expel air
which will show as bubbles in fluid coming
out of tube.
Observe flow, keeping tube submerged in
fluid. When air bubbles cease and stream
is a clean, solid mass, close bleeder screw
tightly. Remove tube.
Repeat operation at each wheel, replenish-
ing the fluid in master cylinder reservoir
Install filler cap and vent tube assembly
in top of master cylinder reservoir.