Specifications
GROUP
2-Bra
kes
secondary (rear brake) master cylin-
der pistons are moved simultaneously
to exert hydraulic fluid pressure on
their respective independent hydraulic
system. The fluid displacement of the
duallmaster cylinders is proportioned
to fulfill the requirements of, each of
the two independent hydraulic brake
systems (Fig. 2).
If a failure of the rear (secondary)
brake system should occur, initial
brake pedal movement causes the un-
restricted secondary piston to bottom
in the master cylinder bore. Primary
piston movement displaces hydraulic
fluid in the primary section of the
dual-master cylinder to actuate the
front brake system.
Should the front (primary) brake
system fail, initial brake pedal move-
ment causes the unrestricted primary
piston to bottom out against the sec-
ondary piston. Continued downward
movement of the brake pedal moves
the secondary piston to displace hy-
draulic fluid in the rear brake sys-
tem, actuating the rear brakes.
The increased pedal travel and the
increased pedal effort required to com-
pensate for the loss of the failed
portion of the brake system provides
a warning that a partial brake system
failure has occured. When the ignition
switch is turned to the START posi-
tion, a dual-brake warning light
pro-
FIG.
I-Power Disc Brake and Power Drum Brake Options
Car Model
Falcon
Fairlane
Mustang
Zi
Comet
Cougar
vides a visual indication the warning
lamp is functional. When the ignition
switch is turned to the
ON
or ACC
position, a dual-brake warning light
on the instrument panel also provides
a visual indication
if
one portion of
the dual-brake system has become
inoperative.
Should a failure of either the front
or rear brake hydraulic system occur,
the hydraulic fluid pressure differen-
tial resulting from the pressure loss
of the failed brake system forces the
valve toward the low pressure area to
illuminate the brake warning light
(Fig: 4).
A
mechanically operated electrical
switch is located on the side of the
pressure differential valve assembly
between the front and rear brake sys-
tem inlet ports. The inner-end of the
spring loaded switch-plunger contacts
the bottom of a tapered shoulder
groove in the center of the valve (Fig.
4). O-ring seals are retained in seal
ring lands near each end of the
valve.
Should a failure
of the rear brake
system occur, hydraulic fluid pressure
in the rear brake system would drop.
During brake pedal operation the fluid
pressure build-up of the front brake
system forces the valve to move to-
ward the low pressure area, or toward
3
Standard with Mustang GT equipment group option, Fairlane GT model.
Mustang brake options available only on eight-cylinder models.
3
Standard for Acc. Fairlane and Comet 427
V-8
Engine,
Power Drum
RPO
RPO
RPO
.
RPO
RPO
FIG.
2-
Dual-Master Cylinder
Power Disc
Not Available
RPO
3
B
RPO
@
RPO
3
.
o
RPO