1993 CHEVROLET DYNASTY Service Manual

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Page 169 of 2438

CHEVROLET DYNASTY 1993 Service Manual Install grease cap and wheel and tire assemblies.
Tighten wheel stud nuts to 115 N Im (85 ft. lbs.)
torque on all models. Install wheel covers.
BRAKE SHOE ASSEMBLIES
Three brake shoe assemblies are

Page 170 of 2438

CHEVROLET DYNASTY 1993 Service Manual Kelsey Hayes ÐLeading/trailing shoes; Remove
holddown springs (Fig. 7). Pull assembly down and
away to remove shoes from support plate (Fig. 8). Re-
move brake shoe springs and adjusting screw assem

Page 171 of 2438

CHEVROLET DYNASTY 1993 Service Manual If old springs have overheated or are damaged, re-
place. Overheating indications are paint discoloration
or distorted end coils. Varga brake springs are not
painted but overheating of the brake spri

If old springs have overheated or are damaged, re-
place. Overheating indications are paint discoloration
or distorted end coils. Varga brake springs are not
painted but overheating of the brake springs will be
noted by any Blueing of the springs.
BRAKE SHOE INSTALLATION
Lubricate the eight shoe contact areas on the sup-
port plate and anchor using Mopar Multi-Purpose
Lubricant or equivalent (Fig. 11).
KELSEY HAYES REASSEMBLE
Assemble the park brake lever and wave washer to
the new replacement shoe (Fig. 9). Attach upper return spring between the two new
shoe assemblies. Apply a small amount of Mopar Multi-Purpose Lu-
bricant or equivalent to the automatic adjuster screw
assembly. Install adjuster with the two stepped forks
facing toward the outboard side of the shoes (Fig.
10). The longer fork will be pointing to the rear. Connect the lower shoe to shoe spring. Expand the automatic adjuster so that the end of the
shoes will clear the wheel cylinder boots. Position the
brake shoe assemblies on support plate and install
holddown springs (Fig. 7). Install self adjuster lever and spring.
Connect park brake cable.
Adjust brake shoes so that they will not interfere
with the drum installation.
CAUTION: Make sure the adjuster screw nut contacts
the adjuster tubular strut.
Install the drums and pump the brake pedal
several times to partially complete the shoe ad-
justment. After adjusting the Parking brake cable (see Adjust-
ing Parking Brake), road test vehicle. The automatic
adjuster will continue the brake adjustment during the
test.
VARGA REASSEMBLE
(1) Install park brake cable in park brake lever of
trailing shoe. (2) Attach trailing shoe, then leading shoe lower
springs to shoes and anchor plate. (3) Position shoes on support plate and install hold-
down springs. (4) Install automatic adjusters. Left side adjuster
has left hand threads and right side adjuster has
right-hand threads. Do not interchange sides.
Make sure adjuster is installed correctly. (Adjuster
ends must be above extruded pins in web of shoe as
shown in Fig. 3). (5) Install upper shoe to shoe spring. Ensure that
the spring terminal ends are fully engaged in the shoe
webs. (6) Rotate serrated adjuster nut to remove free play
from the adjuster assembly. (7) Install the adjuster lever on the leading shoe
pivot pin. Then attach the short end of the adjuster
spring into the hole on the lever. Then install the long
end of the spring in the leading shoe hole. (8) Connect park brake cable and adjust brake shoes
so as not to interfere with drum installation.
BRAKE DRUM REFACING
Measure drum runout and diameter. If not to speci-
fication, reface drum. (Runout should not exceed
0.1524 mm or 0.006 inch). The diameter variation (oval
shape) of the drum braking surface must not exceed
either 0.0635 mm (0.0025 inch) in 30É or 0.0889 mm
(0.0035 inch) in 360É. All drums will show markings of maximum allowable
diameter (Fig. 12).
Fig. 10 Adjuster Screw and Lever (Typical)
Fig. 11 Shoe Contact Areas on Support Plate
Ä BRAKES 5 - 21

Page 172 of 2438

CHEVROLET DYNASTY 1993 Service Manual Using suitable tool, remove grease seal from drum
hub. Clean, inspect and pack wheel bearings. Install
new seal (Fig. 13). See Wheel Bearings section in
this group of the service manual for detailed

Page 173 of 2438

CHEVROLET DYNASTY 1993 Service Manual WHEEL CYLINDERS INDEX
page page
General Information ....................... 23
Installing Wheel Cylinders .................. 24 Service Procedures
....................... 23
GENERAL INFORMATION

WHEEL CYLINDERS INDEX
page page
General Information ....................... 23
Installing Wheel Cylinders .................. 24 Service Procedures
....................... 23
GENERAL INFORMATION
The piston boots are of the push-on type and pre-
vent moisture from entering the wheel cylinder. To perform service operations or inspections of the
rear wheel brake cylinders. It will be necessary to re-
move the cylinders from the support plate and disas-
semble on the bench.
CAUTION: Wheel cylinders with cup expanders
must have cup expanders after any service proce-
dures (reconditioning or replacement).
SERVICE PROCEDURES
REMOVING WHEEL CYLINDERS FROM BRAKE SUPPORT PLATES
With brake drums removed, inspect the wheel cyl-
inder boots for evidence of a brake fluid leak. Then
block the brake pedal in the stroke position, and vi-
sually check the boots for cuts, tears, or heat cracks.
If any of these conditions exist, the wheel cylinders
should be completely cleaned, inspected and new
parts installed. (A slight amount of fluid on the boot
may not be a leak, but may be preservative fluid
used at assembly.) (1) In case of a leak, remove brake shoes, (replace
if soaked with grease or brake fluid.) (2) Thoroughly clean area of wheel cylinder, where
hydraulic brake line connects to wheel cylinder. Dis-
connect hydraulic brake tube from wheel cylinder
(Fig. 1). (3) Remove the rear wheel cylinder attaching bolts
(Fig. 1). Then pull wheel cylinder assembly off the
brake support plate (Fig. 2). (4) Clean the surface sealant off the support plate
and wheel cylinder surfaces.
DISASSEMBLING WHEEL CYLINDERS
To disassemble the wheel cylinders, (Fig. 3) pro-
ceed as follows: (1) Pry boots away from cylinders and remove.
(2) Press INon one piston to force out opposite pis-
ton, cup and spring (with cup expanders). Then using
a soft tool such as a dowel rod, press out the cup and
piston that remain in the wheel cylinder. (3) Wash wheel cylinder, pistons, and spring in
clean brake fluid or alcohol; (DO NOT USE ANY
PETROLEUM BASE SOLVENTS) clean thor- oughly and blow dry with compressed air. Inspect
Fig. 1 Brake Tube Disconnected
Fig. 2 Remove or Install Wheel Cylinder
Ä
BRAKES 5 - 23

Page 174 of 2438

CHEVROLET DYNASTY 1993 Service Manual cylinder bore and piston for scoring and pitting. (Do
not use a rag as lint from the rag will stick to bore
surfaces.) Wheel cylinder bores and pistons that are scored or
pitted in any way should be

cylinder bore and piston for scoring and pitting. (Do
not use a rag as lint from the rag will stick to bore
surfaces.) Wheel cylinder bores and pistons that are scored or
pitted in any way should be replaced. Cylinder walls
that have light scratches, or show signs of corrosion,
can usually be cleaned with crocus cloth, using a cir-
cular motion. Black stains on the cylinder walls are
caused by piston cups and will not impair operation
of cylinder.
ASSEMBLING WHEEL CYLINDERS
Before assembling the pistons and new cups in the
wheel cylinders, dip them in clean brake fluid. If the
boots are deteriorated, cracked or do not fit tightly
on the pistons or the cylinder casting, install new
boots. (1) Coat cylinder bore with clean brake fluid.
(2) Install expansion spring with cup expanders in
cylinder. Install cups in each end of cylinder with
open end of cups facing each other (Fig. 3). (3) Install piston in each end of cylinder having
the flat face of each piston contacting the flat face of
each cup, already installed (Fig. 3). (4) Install a boot over each end of cylinder. Be
careful not to damage boot during installation.
INSTALLING WHEEL CYLINDERS
(1) Apply Mopar tGasket In-A-Tube or equivalent
sealant around wheel cylinder mounting surface (Fig.
4). (2) Install wheel cylinder onto brake support, and
tighten the wheel cylinder to brake support plate at-
taching bolts to 8 N Im (75 in. lbs.). (3) Attach hydraulic brake tube to wheel cylinder,
and tighten tube to wheel cylinder fitting to 17 N Im
(145 in. lbs.). (4) Install brake shoes on support plate.
(5) Install rear brake drum onto rear hub. Install
rear wheel and tire assembly, tighten wheel stud
nuts to 115 N Im (85 ft. lbs.).
(6) Adjust the rear brakes, (See Adjusting Service
Brakes) in Service Adjustments section in this group
of the service manual. (7) Bleed the entire brake system. See (Bleeding
Brake System) in Service Adjustments section in this
group of the service manual.
Fig. 3 Rear Wheel Cylinder
Fig. 4 Apply Sealant on Support Plate
5 - 24 BRAKES Ä

Page 175 of 2438

CHEVROLET DYNASTY 1993 Service Manual BRAKE SUPPORT ASSEMBLY
REMOVAL
Back off parking brake adjusting nut to provide
slack in cable. With wheel and brake drum removed, disconnect
hydraulic tube from wheel cylinder.Disconnect park-
ing b

Page 176 of 2438

CHEVROLET DYNASTY 1993 Service Manual HYDRAULIC SYSTEM CONTROL VALVES INDEX
page page
ABS Brake Proportioning Valve Operation ...... 27
General Information ....................... 26
Hydraulic System Service Procedures ......... 27

HYDRAULIC SYSTEM CONTROL VALVES INDEX
page page
ABS Brake Proportioning Valve Operation ...... 27
General Information ....................... 26
Hydraulic System Service Procedures ......... 27 Non-ABS Proportioning Unit Operation
........ 26
Pressure Differential Warning Light Switch ...... 26
Testing ABS Proportioning Valves ............ 29
GENERAL INFORMATION
Most models not equipped with an Anti-Lock brak-
ing system have a combination hydraulic system con-
trol valve in the brake hydraulic system (Fig. 1). The
valve is attached to the frame rail below the master
cylinder.
The control valve assembly combines a warning
switch with a dual proportioning valve (Fig. 2) Proportioning valves balance front to rear braking
by controlling at a given ratio, the increase in rear
system hydraulic pressure above a preset level. Un-
der light pedal application, the valve allows full hy-
draulic pressure to the rear brakes. There is only one valve assembly in each vehicle,
see Valve Application Chart. During any service pro-
cedures identify valve assemblies by part number as
well as split point (PSI) and slope.
PRESSURE DIFFERENTIAL WARNING LIGHT
SWITCH
The hydraulic brake system, on non-ABS vehicles,
is split diagonally. The left front and right rear
brakes are part of one system. And the right front and left rear are part of another. Both systems are
routed through, but hydraulically separated by a Pres-
sure Differential Switch. The function of the Pressure
Differential Switch is to alert the driver of a malfunc-
tion in the brake system. If hydraulic pressure is lost in one system, the
warning light switch will activate a red light on the
instrument panel, when the brake pedal is depressed.
At this point the brakes require service. However, since
the brake systems are split diagonally the vehicle will
retain 50% of its stopping capability in the event of a
failure in either half. The warning light switch is the latching type. It
will automatically center itself after the repair is
made and the brake pedal is depressed. The instrument panel bulb can be checked each time
the ignition switch is turned to the start position or the
parking brake is set.
NON-ABS PROPORTIONING UNIT OPERATION
The proportioning valve section operates by trans-
mitting full input pressure to the rear brakes up to a
certain point. This is called the split point. Beyond this
point it reduces the amount of pressure increase to the
rear brakes according to a certain ratio. On light pedal applications equal brake pressure will
be transmitted to the front and rear brakes. On heavier
pedal applications the pressure transmitted
Fig. 1 Brake Combination Valve And Warning Switch Location
Fig. 2 Switch and Valve Assembly
5 - 26 BRAKES Ä

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