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BRAKES 5-31
POWER BRAKES
INDEX
General Description
5-31
Maintenance and" Adjustments
5-31
Inspection . . . .
5_31
Lubrication
5-31
Bleeding Instructions . .
. 5.31
Air Cleaner Service . . .
,
5.31
Page
Component Replacement
5-31
Power Brake Cylinder
. . . . . . *
5-31
Removal . .
5-31
Disassembly and Assembly
See Overhaul Manual
Installation . . . .
5-31
GENERAL DESCRIPTION
The Power Brake Unit is a self-contained hydraulic
and vacuum unit, utilizing manifold vacuum and atmos-
phere pressure for its power.
This unit permits the use of a low brake pedal as well
as less pedal effort than is required with the conventional
(nonpower) hydraulic brake system. Only two external
line connections are necessary - one a vacuum connection
from manifold to check valve located on front shell; the
other, a hydraulic connection from the main cylinder
outlet directly into the hydraulic system. The unit is
mounted on the engine side of the fire wall and directly
connected to the brake pedal.
MAINTENANCE AND ADJUSTMENTS
INSPECTIONS
1. Check vacuum line and vacuum line connections as
well as vacuum check valve in front shell of power
unit for possible vacuum loss.
2. Inspect all hydraulic lines and connections at the
wheel cylinders and main cylinder for possible
hydraulic leaks.
3. Check brake assemblies for scored drums, grease
or brake fluid on linings, worn or glazed linings,
and make necessary adjustments.
4. Check brake fluid level in the hydraulic reser-
voirs. The reservoirs should be filled to the levels
shown in Figure 8.
5. Check for loose mounting bolts at main cylinder and
at power section.
6. Check air cleaner filter in power piston extension
and replace filter if necessary.
7. Check brake pedal for binding and misalignment
between pedal -and push rod.
LUBRICATION
The power brake unit is lubricated at assembly and
needs no further lubrication other than maintaining
normal reservoir fluid level. The reservoir should be
filled as described in this section.
BLEEDING INSTRUCTIONS
The power system may be bled manually or with a
pressure bleeder as outlined in this section. Use only
GM Supreme 11 Brake Fluid or equivalent. Do not use the
power assist while bleeding. The engine should not be
running and the vacuum reserve should be reduced to
zero by applying the brake several times before starting
the bleeding procedure.
AIR CLEANER SERVICE
Servicing of the air cleaner is recommended and the
element
replaced when restriction becomes severe
enough to affect power brake response. At any other
time, if cleaning of the filter is felt necessary, it should
be shaken free of dirt or washed in soap and water and
thoroughly dried.
COMPONENT REPLACEMENT
POWER BRAKE CYLINDER
Removal
1. Remove vacuum hose from vacuum check valve.
2. Disconnect hydraulic lines at main cylinder.
Disconnect push rod at brake pedal assembly.
Remove nuts and lock washers securing power unit
to fire wall, and remove power unit from engine
compartment.
3.
4.
NOTE: Chevy
to fire wall.
has a three stud attachment
Repair procedures for the power cylinder are outlined
in the Brake Section of the Overhaul Manual-for service
of the main cylinder refer to applicable portion of
"Standard Brakes" in this manual.
Installation
1. Mount the power brake assembly in place and install
the attaching nuts and lock washers.
2. Attach vacuum line to check valve.
3. Secure hydraulic lines to main cylinder.
4. Attach push rod to brake pedal assembly, and check
operation of stop light.
5. Bleed brakes as outlined in this section.
CAUTION: After replacing the unit on the vehi-
cle, start the engine and allow vacuum to build
up before applying the brake.
CHEVROLET CHASSIS SERVICE
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