service CHEVROLET DYNASTY 1993 Repair Manual

TESTING APPLICATION ADJUSTER OPERATION
Place the vehicle on a hoist with a helper in the
driver's seat to apply the brakes. Remove the access
plug from the rear adjustment slot in each brake
support plate (Fig. 4) to provide access to the ad-
juster star wheel. Then, to eliminate the possibility
of maximum adjustment, where the adjuster does not
operate because the closest possible adjustment has
been reached. Back the star wheel off approximately
30 notches. It will be necessary to hold the adjuster
lever away from the star wheel to permit this adjust-
ment. Spin the wheel and brake drum in the reverse di-
rection, and with a greater than normal force apply
the brakes suddenly. This sudden application of force
will cause the secondary brake shoe to leave the an-
chor. The wrap up effect will move the secondary
shoe, and the cable will pull the adjuster lever up.
Upon application of the brake pedal, the lever should
move upward, turning the star wheel. Thus, a defi-
nite rotation of the adjuster star wheel can be ob-
served if the automatic adjuster is working properly.
If one or more adjusters do not function properly, the
respective drum must be removed for adjuster servic-
ing.
BLEEDING BRAKE SYSTEM
CAUTION: For bleeding of the Anti-Lock brake hy-
draulic system. See the Anti-Lock Brake system
service procedures in this group which refers to the
particular Anti-Lock brake system being serviced.
PRESSURE BLEEDING
Before removing the master cylinder cover, wipe it
clean to prevent dirt and other foreign matter from
dropping into the master cylinder. CAUTION: Use bleeder tank Special Tool C-3496-B
with adapter Special Tool C-4578 to pressurize the
system for bleeding.
Follow pressure bleeder manufacturer's instruc-
tions, for use of pressure bleeding equipment. When bleeding the brake system. Some air may be
trapped in the brake lines or valves far upstream. As
much as ten feet from the bleeder screw (Fig. 6).
Therefore, it is essential to have a fast flow of a large
volume of brake fluid when bleeding the brakes to
ensure all the air gets out.
The following wheel sequence for bleeding the
brake hydraulic system should be used to ensure ad-
equate removal of all trapped air from the hydraulic
system.
² Right rear wheel
² Left front wheel
² Left rear wheel
² Right front wheel
To bleed the brake system. Attach a clear plastic
hose to the bleeder screw starting at the right rear
wheel and feed the hose into a clear jar containing
fresh brake fluid (Fig. 7). Next, open the bleeder screw at least one full turn
or more to obtain an adequate flow of brake fluid
(Fig. 8).
CAUTION: Just cracking the bleeder screw often re-
stricts fluid flow, and a slow, weak fluid discharge
will NOT get all the air out.
After 4 to 8 ounces of fluid has been bled through
the brake system at this wheel. And an air-free flow
is maintained in the clear plastic hose and jar, this
will indicate a good bleed. Repeat the procedure at all the other remaining
bleeder screws. Then check the pedal for travel. If
pedal travel is excessive or has not been improved.
Enough fluid has not passed through the system to
Fig. 5 Brake Drum Adjustment With Tool C-3784
Fig. 6 Trapped Air in Brake Line
5 - 6 BRAKES Ä

BRAKE HOSE AND TUBING
INSPECTION OF BRAKE HOSE AND TUBING
Flexible rubber hose is used at both front brakes and
at the rear axle. Inspection of brake hoses should be
performed whenever the brake system is serviced and
every 7,500 miles or 12 months, whichever comes first
(every engine oil change). Inspect hydraulic brake
hoses for severe surface cracking, scuffing, or worn
spots. Should the fabric casing of the rubber hose be
exposed due to cracks or abrasions in the rubber hose
cover, the hose should be replaced immediately. Even-
tual deterioration of the hose can take place with
possible burst failure. Faulty installation can cause
twisting and wheel, tire or chassis interference. The steel brake tubing should be inspected periodi-
cally for evidence of physical damage or contact with
moving or hot components.
INSTALLATION OF BRAKE HOSE
Always use factory recommended brake hose to en-
sure quality, correct length and superior fatigue life.
Care should be taken to make sure that the tube and
hose mating surfaces are clean and free from nicks and
burrs. Front right and left side hoses are not
interchangeable. Connections should be correct and properly made.
Use new copper seal washers on all connections using
Banjo Bolts and tighten all fittings to their specified
torques. The flexible front hydraulic brake hose should al-
ways be installed on the vehicle by first attaching the
Banjo connector to the caliper assembly. Then bolt the
intermediate hose bracket to the strut assembly allow-
ing the bracket to position the hose to prevent twisting.
Attach the hose to the body bracket and steel brake
tubing. Tighten all fittings to specified torque. The
body bracket and hose end are keyed so that they will
only fit one way. Install rear brake hoses first to the trailing arm
tubes and then to the floor pan tubes. Minimize hose
twisting. Vehicles equipped with rear disc brakes have
brake hoses attached to the caliper on each side. The
brake hose should be first attached by the Banjo bolt to
the caliper and then secured to the hose bracket with
the retaining clip. The attach the steel brake tubing to
the hose fitting.
REPAIR AND INSTALLATION OF BRAKE TUB- ING
Only double wall 4.75mm (3/16 in.) steel tubing
should be used for replacement. Care should be taken
when replacing brake tubing, to be sure the proper
bending and flaring tools and procedures are used, to
avoid kinking. Do not route the tubes against sharp edges, moving components or into hot areas. All
tubes should be properly attached with recommended
retaining clips.
TYPES OF TUBING FLARES
Two different tubing flares (Fig. 13) are used on 93
M.Y. vehicles. On some ABS brake systems the tub-
ing connections made to the hydraulic assembly use
an ISO flare. All other ABS brake system compo-
nent, tubing connections are made using a double in-
verted flare. On non-ABS brake systems all
component tubing connections use only the double in-
verted flare. No ISO flares are used.
CAUTION: ALWAYS USE THE PROPER FLARING
TOOL AND PROCEDURE, FOR THE TYPE OF
BRAKE SYSTEM THAT IS BEING SERVICED TO IN-
SURE THE INTEGRITY OF THE HYDRAULIC SYS-
TEM.
TO REPAIR OR FLARE TUBING
Using Tubing Cutter, Special Tool C-3478-A or
equivalent, cut off damaged seat or tubing (Fig. 14).
Ream out any burrs or rough edges showing on in-
side of tubing (Fig. 15). This will make the ends of
tubing square (Fig. 15) and ensure better seating of
flared end tubing. PLACE TUBE NUT ON TUB-
ING BEFORE FLARING THE TUBING.
DOUBLE INVERTED TUBING FLARES.
To make a double inverted tubing flare (Fig. 13 &
16). Open handles of Flaring Tool, Special Tool
C-4047 or equivalent. Then rotate jaws of tool until
the mating jaws of tubing size are centered between
vertical posts on tool. Slowly close handles with tub-
Fig. 13 Identifying Hydraulic Brake Tubing Flares
Ä BRAKES 5 - 11

ing inserted in jaws but do not apply heavy pressure
to handle as this will lock tubing in place.Place gauge (Form A) on edge over end of brake
tubing. Push tubing through jaws until end of tubing
contacts the recessed notch in gauge matching the
tubing size. Squeeze handles of flaring tool and lock
tubing in place. Place 3/16 inch plug of gauge (A)
down in end of tubing. Swing compression disc over
gauge and center tapered flaring screw in recess of
disc. Screw in until plug gauge has seated on jaws of
flaring tool. This action has started to invert the ex- tended end of the tubing. Remove gauge and continue
to screw down until tool is firmly seated in tubing.
Remove tubing from flaring tool and inspect seat. Refer
to routing diagrams (Figs. 18 to 21) for proper routing
and clip location. Replace any damaged tube routing
clips.
ISO TUBING FLARES
CAUTION: All ISO style tubing flares (Fig. 13 & 16 ) are
of metric dimensions. When performing any service
procedures on vehicles using ISO style tubing flares,
metric size tubing of 4.75 mm MUST be used with
metric ISO tube flaring equipment.
To create a (metric) ISO style tubing flare, Use
Snap-On Flaring Tool TFM-428, or equivalent. See
(Fig. 17) and proceed with the steps listed below. Be
sure to place the tubing nut on the tube before
flaring the tubing. (1) Carefully prepare the end of the tubing to be
flared. Be sure the end of the tubing to be flared is
square and all burrs on the inside of the tubing are
removed (Fig. 15). This preparation is essential to
obtain the correct form of a (metric) ISO tubing
flare. (2) Open the jaws of the Flaring Tool. Align the
mating size jaws of the flaring tool around the size of
the tubing to be flared. Close the jaws of the Flaring
Tool around the tubing to keep it from sliding out of the
flaring tool, but do not lock the tubing in place. See
(Fig. 17)
Fig. 14 Cutting and Flaring of Brake Line Tubing
Fig. 15 Brake Tube Preparation For Flaring
Fig. 16 Double Flare And ISO-Flare Tubing Connec- tions
5 - 12 BRAKES Ä

REAR WHEEL DRUM BRAKES INDEX
page page
Brake Drum Refacing ..................... 21
Brake Shoe Assemblies ................... 19 Description
............................. 18
Service Procedures ....................... 18
DESCRIPTION
Rear wheel drum brakes (Fig .2&3)aretwoshoe,
internal expanding type with an automatic adjuster
screw assembly that is activated each time the
brakes are applied. The automatic adjuster screw is
located directly below the wheel cylinder as shown in
figure (Fig .2&3).
WARNING: DUST AND DIRT ON BRAKE PARTS
GENERATED DURING THE NORMAL USE AND
WEAR OF MOTOR VEHICLE BRAKE SYSTEMS MAY
CONTAIN ASBESTOS FIBERS. BREATHING EXCES-
SIVE CONCENTRATIONS OF ASBESTOS FIBERS
CAN CAUSE SERIOUS BODILY HARM, SUCH AS
ASBESTOSIS AND CANCER. EXTREME CARE
SHOULD BE EXERCISED WHILE SERVICING
BRAKE ASSEMBLIES OR COMPONENTS. DO NOT CLEAN BRAKE ASSEMBLIES OR COM-
PONENTS WITH COMPRESSED AIR OR BY DRY
BRUSHING; USE A VACUUM CLEANER SPECIFI-
CALLY RECOMMENDED FOR USE WITH ASBES-
TOS FIBERS. IF A SUITABLE VACUUM CLEANER IS
NOT AVAILABLE, CLEANING SHOULD BE DONE
WET USING A WATER DAMPENED CLOTH. DO NOT CREATE DUST BY SANDING, GRINDING,
AND/OR SHAVING BRAKE LININGS OR PADS UN-
LESS SUCH OPERATION IS DONE WHILE USING
PROPERLY EXHAUST VENTILATED EQUIPMENT. DISPOSE OF ALL DUST AND DIRT SUSPECTED
TO CONTAIN ANY ASBESTOS FIBERS IN SEALED
BAGS OR CONTAINERS TO MINIMIZE DUST EXPO-
SURE TO YOURSELF AND OTHERS. FOLLOW ALL RECOMMENDED PRACTICES PRE-
SCRIBED BY THE OCCUPATIONAL SAFETY AND
HEALTH ADMINISTRATION AND THE ENVIRON-
MENTAL PROTECTION AGENCY. FOR THE HAN-
DLING, PROCESSING, AND DISPOSITION OF DUST
OR DIRT WHICH MAY CONTAIN ASBESTOS FI-
BERS. IT IS RECOMMENDED NOT TO BREATH ANY
TYPE OF BRAKE LINING MATERIAL DUST EVEN
ASBESTOS FREE, DUE TO THE FIBROUS NATURE
OF THE MATERIALS BEING USED.
SERVICE PROCEDURES
REAR BRAKE DRUM REMOVAL
If the rear brake drum is difficult to remove, fur-
ther clearance can be obtained by backing off the
brake automatic adjuster screw. Remove rubber plug
from the top of the support plate and rotate the au-
tomatic adjuster screw assembly with an upward mo-
tion, using the Brake Adjuster, Special Tool C-3784. See adjusting rear service brakes in the Service
Adjustments section in this group of the service man-
ual for the specific adjustment procedure. Remove wheel bearing grease cap (Fig. 1).
Remove cotter pin, nut lock, retaining nut, thrust
washer and outer bearing cone (Fig. 1). Remove brake drum and hub and bearing assembly
from the rear spindle (Fig. 1). Inspect brake linings for wear, shoe alignment and
contamination.
BRAKE DRUM INSTALLATION
Install brake drum and hub and bearing assembly
on rear spindle. Install outer wheel bearing, thrust washer and nut.
Tighten wheel bearing adjusting nut to 27 to 34
N Im (240 to 300 in. lbs.) torque while rotating hub.
This seats the bearings. Back off adjusting nut 1/4 turn (90É) then tighten
adjusting nut finger tight. Position lock on nut with one pair of slots in-line
with cotter pin hole. Install cotter pin.
Fig. 1 Brake Drum and Hub Assembly
5 - 18 BRAKES Ä

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