Buick LeSabre 1965 Service Manual page 560

9 - 3 8 POWER BRAKES
BRAKES
GROUP 9-E
BENDIX POWER BRAKES
CONTENTS IN SECTION 9-E
Paragraph Subject Page
9-22 Description of Power
Brake Mechanism 9-38
9-23 Operation of Power Brake 9-39
9-24 Removal, Installation, Adjusting and
Testing of Power Brake Unit . . . 9-41
Paragraph Subject Page
9-25 Disassembly of Power Brake . . . . 9-44
9-26 Cleaning and Inspection of Parts . . 9-44
9-27 Assembly of Power Brake 9-45
9-28 Gauging Power Brake 9-48
9 - 2 2 DESCRIPTION OF
POWER BRAKE
MECHANISM
The Bendix Power Brake Unit is
a self-contained vacuum hydraulic
power braking unit. It is of the
vacuum suspended type which uti-
lizes engine intake manifold vacu-
um and atmospheric pressure for
its power. It consists of three
basic elements combined into a
single unit. See Figures 9-34 and
9-35.
The three basic elements are as
follows:
1. A vacuum power chamber con-
sisting of a front and rear hous-
ing, a diaphragm, a power piston,
a hydraulic push rod and a power
piston return spring.
2. A mechanically actuated con-
trol valve, integral with the vac-
uum power piston, controls the
degree of power brake applica-
tion or release in accordance with
the foot pressure applied to the
valve operating rod through the
brake pedal linkage. The control
valve consists of a single poppet
and an atmospheric port and a
vacuum port. The vacuum port
seat is a part of the valve body
attached to the power piston as-
sembly. The atmospheric port
seat is a part of the valve plunger
which moves within the valve
h o u s i n g and power p i s t o n
assembly.
3. A single piston hydraulic mas-
ter cylinder of the Lealed type is
used with the power brake and
contains all of the elements of
Figure 9-34—External View of Power Brake
the conventional brake master
cylinder except for the hydraulic
push rod which is of special de-
sign. In the sealed type of master
cylinder, a flexible diaphragm,
located between the fluid reser-
voir and the vented filler cover,
seals the fluid in the systems
from outside air and dust while
maintaining normal atmospheric
pressure on the fluid in the fluid
reservoir.
The power piston assembly and
the components which make up
the valve assembly are connected
to the brake pedal through the
valve operating rod and pedal
linkage. The valve operating rod
is connected to the air valve
plunger which moves within the
power piston assembly. A valve
return spring r e t u r n s the air
valve plunger and v a l v e rod
to the released position when
pressure is released from the
brake pedal. The floating control
valve is of the flexible rubber
type and is supported by the valve
body. In the released position
the floating control valve return
spring holds the poppet against
the atmospheric port seat. A
special bearing and seal is used