TM 5-3805-258-24-1
A I R S Y S T E M A N D B R A K E S
H Y D R A U L I C C I R C U I T F O R T H E
W H E E L B R A K ES
BRAKE FLUID RESERVOIRS
Reservoirs (1) and (2) are under a tool box at the
rear of the cab, and are the brake fluid supply for
the hydraulic circuit of the wheel brakes. Any extra
brake fluid needed to activate the wheel brakes
comes from the reservoirs.
Reservoir (1) provides brake fluid for the rear
brakes and reservoir (2) provides brake fluid for
the front brakes. When the brakes are released,
the pressure in the lines is released to the reservoirs.
L O C A T I O N O F B R A K E F L U I D R E S E R V O I R S
1. Reservoir for rear wheel brakes. 2. Reservoir for front
wheel brakes.
MASTER CYLINDERS
R E A R O F C A B
S Y S T E M S O P E R A T I O N
The two master cylinders are part of the air/
hydraulic cylinders. Master cylinders (2) and (4)
are under the tool box at the rear of the cab.
Each master cylinder sends brake fluid to the
wheel brakes on one axle. The brake fluid pressure
in the master cylinder is 16 times the amount of
air pressure in the air cylinder. Master cylinder (2)
sends brake fluid to the rear axle and master cyl-
inder (4) sends brake fluid to the front axle.
Operation
Air pressure from the air circuit for the wheel
brakes goes through air inlet (11) and moves piston
(12) and rod (13) to the right. Rod (13) pushes on
valve (9) and valve insert (15). Valve insert (15)
closes make-up fluid inlet (8). More movement of
rod (13) pushes power piston (14). The power piston
pushes brake fluid in cylinder (17) through fluid
outlet (18) and through the lines to the wheel cyl-
inders. This activates (engages) the wheel brakes.
When the air pressure decreases at air inlet (11),
spring (7) in air cylinder (6) moves rod (13) and
piston (12) to the left. This also causes power piston
(14) to move the the left. Make-up fluid from brake
fluid reservoirs is at the left side of power piston
(14). When the brakes are released, rod (13) and
piston (12) go back (return) to their original posi-
tions. At this time, if make-up fluid is needed in
cylinder (17) it comes through make-up fluid inlet
(8). This make-up fluid goes around the flat sides
of valve (9) and around valve insert (15), through
passage (16) in power piston (14) into cylinder (17).
The operation of valve (9) and valve insert (15)
does not permit the hydraulic circuit to have a
vacuum.
Bleeder screw (10) is used to remove any air
inside the master cylinder [cylinder (17)].
1. Air cylinder for rear wheel brakes. 2. Master cylinder
f o r r e a r w h e e l b r a k e s . 3 . A i r c y l i n d e r f o r f r o n t w h e e l
b r a k e s . 4 . M a s t e r c y l i n d e r f o r f r o n t w h e e l b r a k e s . 5 .
Brake fluid pressure (overstroke) switches.
3-86
