1993 CHEVROLET DYNASTY service

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 used on the front
wheel drive passenger cars. Vehicles will have axle
sets of either 200 or 220 mm Kelsey Hayes (Fig. 2),
or Varga (Fig. 3). Varga brake shoes are HANDED
for right or left side. Except for brake shoe to support plate, park brake
lever retention and automatic adjuster positioning
guide buttons, service procedures for either assembly
are essentially the same.REMOVAL
Remove automatic adjuster spring and lever (Fig.
4).
Rotate the automatic adjuster screw assembly so
that each shoe assembly moves out far enough to be
free from the wheel cylinder boots (Fig. 5).
Disconnect the parking brake cable from the park-
ing brake lever (Fig. 6).
Fig. 2 Kelsey Hayes 200 And 220 (Left) Rear Wheel Brake
Fig. 3 Varga (Left) Rear Wheel Brake
Fig. 4 Remove or Install Adjuster Lever Spring
Fig. 5 Expand or Retract Adjuster Screw
Ä BRAKES 5 - 19

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 infor-
mation on the wheel bearings, and service proce-
dures.
Fig. 12 Maximum Drum Diameter IdentificationFig. 13 Installing Grease Seal
5 - 22 BRAKES Ä

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

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

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 brake cable and adjuster lever spring (Fig. 1).
Using a suitable tool such as an aircraft type hose
clamp, install the clamp over the retainer on the end
of the parking brake cable (Fig. 2). Compress cable
housing retainer and start housing out of support
plate (Fig. 2). Remove clamp when retainer is free
from the park brake cable mounting hole in the rear
brake support plate. Alternate method is to slide a
14 mm box wrench over housing end fitting com-
pressing the three fingers. Remove attaching bolts and washers and separate
brake support and spindle from rear support trailing
arm.
INSTALLATION
Insert parking brake cable and housing into sup-
port plate. Install support plate, spindle and gasket between
support plate and spindle on to rear suspension mem-
ber. Tighten support plate attaching bolts to 71 N Im
(53 ft. lbs) torque. Attach cable to parking brake lever.
Connect brake tube to wheel cylinder. Tighten
brake tube to wheel cylinder fitting to 17 N Im (145
in. lbs.). Install brake drum and wheel. Adjust and bleed
service brakes. Adjust parking brake.
Fig. 1 Removing Adjuster Lever Spring
Fig. 2 Removing Park Brake Cable From Support Plate
Ä BRAKES 5 - 25

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

to the rear will be lower than the front brakes. This will
prevent premature rear wheel lock-up and skid. If
hydraulic pressure is lost in one half of the diagonally
split system, the operation of the proportioning valve
in the remaining half is not effected.
ABS BRAKE PROPORTIONING VALVE OPERATION
On vehicles using the ABS braking system, screw in
proportioning valves are used in place of the conven-
tional differential pressure/proportioning valve. Each rear brake circuit has its own screw-in propor-
tioning valve which is attached to the rear brake outlet
ports of the hydraulic assembly. These valves limit
brake pressure to the rear brakes after a certain
pressure is reached. This improves front to rear brake
balance during normal braking.
Screw in proportioning valves can be identified by
the numbers stamped on the body of the valve. The
first digit represents the slope, the second digit repre-
sents the split (cut-in) point, and the arrow represents
the flow direction of the valve. Be sure that the
numbers listed on the replacement valve are the
same as on the valve that is being removed. See
(Fig. 3) for detail of the valve identification.
HYDRAULIC SYSTEM SERVICE PROCEDURES
BRAKE WARNING SYSTEM
CHECKING BRAKE WARNING SWITCH UNIT
The Red Brake Warning light will come on when
the parking brake is applied with the ignition key
turned ON. The same light will also illuminate
should one of the two service brake hydraulic sys-
tems fail.
CAUTION:Make sure air does not enter the hydrau-
lic system during this test procedure. See bleeding
without a pressure bleeder at the beginning of this
section for master cylinder fluid level checking pro-
cedures.
To test the service brake warning system lamp.
Raise the vehicle on a hoist and open a wheel cylin-
der bleeder while a helper depresses the brake pedal
and observes the warning light. If the light fails to light, inspect for a burned out
bulb, disconnected socket, or a broken or discon-
nected wire at the switch. If the bulb is not burned
out and the wire continuity is uninterrupted. Check
the service brake warning switch operation with a
test lamp between the switch terminal and a known
good ground. Be sure to fill master cylinder and
bleed brake system after correction has been made, if
necessary.
PROPORTIONING VALVES
TESTING PROPORTIONING VALVE UNIT
If premature rear wheel skid occurs on hard brake
application, it could be an indication that a malfunc-
tion has occurred with the proportioning valve unit. The proportioning valve is designed with two sep-
arate systems. One half controls the right rear
brake, and the other half controls the left rear brake.
Therefore, a road test to determine which rear brake
slides first is essential.
RIGHT REAR WHEEL SLIDES FIRST To test the proportioning valve when the right rear
wheel slides first, leave the front brakes connected to
the valve, proceed as follows: (1) Install one gauge and (TEE) of set C-4007-A
between the brake line from the master cylinder sec-
ondary port and the brake valve assembly. (2) Install the second gauge of set C-4007-A to the
right rear brake outlet port (Fig. 4). Using an
adapter tube, made from a short piece of brake tube
and (2) 3/8 x 24 tube nuts. Connect the hose to the
valve. Bleed the hose and gauge. (3) Have a helper exert pressure on the brake
pedal (holding pressure) to get a reading on the valve
inlet gauge and check the reading on the outlet
Fig. 3 ABS PROPORTIONING VALVE IDENTIFICA- TION
Ä BRAKES 5 - 27

FRONT DISC BRAKES INDEX
page page
General Information ....................... 31
Service Precautions ....................... 34 Shoe and Lining Wear
.................... 33
GENERAL INFORMATION
The single piston, floating caliper disc brake as-
sembly (Fig. 1 and 2) consists of:
² The driving hub
² Braking disc (rotor)
² Caliper assembly
² Shoes and linings
² Adapter for mounting the caliper assembly to the
steering knuckle WARNING: THE PISTONS THAT ARE USED
IN THE 2 DIFFERENT CALIPER ASSEMBLIES
ARE UNIQUE TO THE CALIPER THEY ARE
USED IN. THE DIMENSIONS OF THESE PIS-
TONS ARE DIFFERENT, DO NOT INTER-
CHANGE THE CALIPER PISTONS.
IMPROPER USE COULD CAUSE A COM-
PLETE FAILURE OF THE BRAKE SYSTEM. The double pin Kelsey-Hayes Family Caliper, is
mounted to the adapter using bushings, sleeves and
2 through bolts threaded into the adapter (Fig. 3 and
5). The adapter is then mounted to the steering
knuckle using 2 attaching bolts. The double pin Kelsey-Hayes Non-Family Caliper,
is mounted directly to the steering knuckle of the ve-
hicle using bushings, sleeves and 2 through bolts (Fig. 4). The adapter is not used on the vehicles
equipped with the Non-Family caliper assembly.
Two machined abutments on the caliper mounting
adapter or steering knuckle, (Fig. 3 and 4) position
the caliper fore and aft. The guide pin bolts, sleeves
and bushings control the float, side to side movement
of the caliper. The piston seal, is designed to pull the
piston back into the bore of the caliper when the
brake pedal is released. This maintains proper brake
shoe to rotor clearance (Fig. 6). Vehicles equipped with Kelsey-Hayes double pin
family calipers, have 1 anti-rattle clip attached to
the top of the adapter (Fig. 1). All of the braking force is taken up directly by the
adapter or the steering knuckle depending on the
type of caliper assembly the vehicle is equipped with. The caliper is a one piece casting with the inboard
side containing a single piston cylinder bore. The front disc brake caliper phenolic piston is 2 dif-
ferent sizes depending on the vehicle that the caliper
assembly is used on. The AC, AG & AY body use a
60 mm piston, and the AA, AP, AG & AJ body use a
54 mm piston.
Fig. 1 Front Disc Brake Assembly (Family Caliper Typical)
Ä BRAKES 5 - 31