brakes CHEVROLET DYNASTY 1993 Repair Manual

removal will be necessary. Remove the shoe and lin-
ing assemblies (see Brake Shoe Removal).Combined shoe and lining thickness should be
measured at the thinnest part of the assembly. When a shoe and lining assembly is worn to a
thickness of approximately 7.0 mm (9/32 inch) it
should be replaced. Replace both shoe assemblies (inboard and out-
board) on both wheels whenever shoe assemblies on
either side are replaced. If a shoe assembly does not require replacement.
Reinstall it, making sure each shoe assembly is re-
turned to its original position on the wheel of the ve-
hicle from which it was removed. (See Brake Shoe
Installation).
SERVICE PRECAUTIONS
WARNING: DUST AND DIRT ON BRAKE PARTS
GENERATED DURING THE NORMAL USE AND
WEAR OF MOTOR VEHICLE BRAKE SYSTEMS CAN
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, GRINDIN-
G,AND/OR SHAVING BRAKE LININGS OR PADS
UNLESS 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.
Grease or any other foreign material must be kept
off the caliper assembly, surfaces of the braking disc
and external surfaces of the hub, during service pro-
cedures. Handling the braking disc and caliper should be done
in such a way as to avoid deformation of the disc and
scratching or nicking the brake linings (pads). During removal and installation of a wheel and tire
assembly, use care not to strike the caliper. Before vehicle is moved after any brake service
work, be sure to obtain a firm brake pedal.
BRAKE SHOE REMOVAL
(1) Raise vehicle on jackstands or centered on a
hoist. (2) Remove rear wheel and tire assemblies.
(3) Remove caliper attaching bolts (Fig. 2).
(4) Lift caliper away from adapter rails (Fig. 3).
(5) Remove outboard shoe. By prying the shoe re-
taining clip over the raised area on the caliper. Then
slide the shoe down and off the caliper (Fig. 4). (6) Pull inboard shoe away from piston, until the
retaining clip is free from the cavity in the piston. (Fig.
5).
CLEANING AND INSPECTION
Check for piston seal leaks (brake fluid in and
around boot area and inboard lining) and for any
ruptures of piston dust boot. If the boot is damaged, or
fluid leak is visible, disassemble caliper assembly and
install a new seal and boot (and piston if scored). Refer
to procedure titled Disc Brake Caliper Disassembly.
BRAKE SHOE INSTALLATION
(1) Retract piston.
If the originally removed brake shoe assem-
blies are to be replaced back on vehicle. Be sure
Fig. 2 Removing Caliper Attaching Bolts
5 - 46 BRAKES Ä

each brake shoe assembly is returned to its origi-
nal position on the wheel of the vehicle from
which it was removed. (2) Install inboard brake shoe by inserting shoe
retaining clip into piston cavity. Be sure brake shoe is
seated squarely on the face of the piston. (Fig. 5). (3) Install outboard shoe by sliding retaining clip
over caliper fingers. Be sure the brake shoe is installed
on the caliper, so the retaining clip is past the raised
area on the caliper fingers (Fig. 6). (4) Install lower end of caliper on to adapter. Make sure the lower tabs on the brake shoes and the cast-
ing projections on the caliper are under the adapter
rail (Fig. 7). (5) Rotate caliper down over rotor.
(6) Install caliper attaching bolts and tighten to 22
N Im (193 in. lbs.) torque (Fig. 8).
(7) Install wheel and tire assembly. Tighten stud
nuts in proper sequence until all nuts are torqued to
half specification. This is important. Then repeat
sequence to full specification. (8) Remove jackstands or lower hoist. Before mov-
ing vehicle be sure it has a firm pedal.
Fig. 5 Remove and Install Inboard Brake Shoe
Fig. 6 Installing Outboard Shoe
Fig. 3 Removing Caliper
Fig. 4 Removing Outboard Shoe
Ä BRAKES 5 - 47

DISASSEMBLING REAR CALIPER ASSEMBLY
CLEANING AND INSPECTION
Check for piston fluid seal leaks (brake fluid in and
around boot area and inboard lining) and for any
ruptures of piston dust boot. If boot is damaged, or
fluid leak is visible, disassemble caliper assembly
and install a new seal and boot,(and piston if scored).
Refer to procedures titled Disc Brake Caliper Disas-
sembly. Check the caliper dust boot and caliper pin bush-
ings to determine if they are in good condition. Re- place if they are damaged, dry, or found to be brittle.
Refer to Cleaning And Inspection Of Brake Caliper. (1) Remove caliper from braking disc (See Brake
Shoe Removal). Hang assembly on a wire hook away
from braking disc, so hydraulic fluid cannot get on
braking disc (See Fig. 4 in Brake Shoe Removal). Place
a small piece of wood between the piston and caliper
fingers. (2) Carefully depress brake pedal to hydraulically
push piston out of bore. (Brake pedal will fall away
when piston has passed bore opening.) Then prop up
the brake pedal to any position below the first inch of
pedal travel, this will prevent loss of brake fluid from
the master cylinder. (3) If both front caliper pistons are to be removed,
disconnect flexible brake line at frame bracket after
removing piston. Plug brake tube and remove piston
from opposite caliper. Using the same process as above
for the first piston removal.
WARNING: UNDER NO CONDITION SHOULD AIR
PRESSURE BE USED TO REMOVE PISTON FROM
CALIPER BORE. PERSONAL INJURY COULD RE-
SULT FROM SUCH A PRACTICE.
(4) Disconnect brake flexible hose from the caliper.
To disassemble, mount caliper assembly in a vise
equipped with protective jaws.
CAUTION: Excessive vise pressure will cause bore
distortion and binding of piston.
Support rear caliper assembly in a vise. Then remove
caliper to piston dust boot and discard (Fig. 1).
Using a plastic trim stick, work piston seal out of its
groove in caliper piston bore (Fig. 2). Discard old seal.
Do not use a screwdriver or other metal
Fig. 7 Installing Caliper
Fig. 8 Installing Attaching Bolts
Fig. 1 Removing Piston Dust Boot
5 - 48 BRAKES Ä

tool for this operation, because of the possibility
of scratching piston bore or burring edges of seal
groove. The double pin caliper uses a sealed for life bushing
and sleeve assembly. If required this assembly can be
serviced using the following procedure. (1) Using your fingers push on one end the inner
sleeve until it pops out of the bushing. Then grasp the
inner sleeve with your fingers and pull the inner sleeve
out from the inside of the bushing (Fig. 3). (2) Using your fingers collapse one side of the bush-
ing. Then pull on the opposite side to remove the
bushing from the caliper assembly (Fig. 4).
CLEANING AND INSPECTION
Clean all parts using alcohol or a suitable solvent
and wipe dry. Clean out all drilled passages and bores
on the caliper assembly body. (Whenever a caliper
has been disassembled, a new boot and seal must
be installed at assembly). Inspect the caliper assembly piston bore for scoring
or pitting. Bores that show light scratches or corrosion,
can usually have the scratches or corrosion removed
using crocus cloth. Bores that have deep scratches or scoring should be
honed. Use Caliper Hone, Special Tool C-4095, or
equivalent providing the diameter of the bore is not
increased more than 0.0254 mm (0.001 inch) (Fig. 5). If the bore does not clean up within this specification,
a new caliper housing should be installed. Install a new
piston if the old one is pitted or scored. When using Caliper Honing Tool, Special Tool
C-4095, coat the stones and bore with brake fluid.
After honing the bore, carefully clean the seal
and boot grooves with a stiff non-metallic rotary
brush. Use extreme care in cleaning the caliper after
honing. Remove all dirt and grit by flushing the
caliper with brake fluid; wipe dry with a clean,
lint free cloth and then clean a second time.
ASSEMBLING REAR DISC BRAKE CALIPER
Clamp caliper in vise (with protective caps on vise
jaws).
Fig. 2 Removing Piston Seal
Fig. 3 Removing Inner Sleeve From Bushing
Fig. 4 Removing Bushings From Caliper
Ä BRAKES 5 - 49

CAUTION: Excessive vise pressure will cause bore
distortion and binding of piston. Dip new piston seal in clean brake fluid and install
in the groove of the caliper bore. Seal should be po-
sitioned at one area in groove and gently worked
around the groove (Fig. 6), using only your fingers
until properly seated. NEVER USE AN OLD PISTON SEAL. (Be sure
that fingers are clean and seal is not twisted or
rolled) (Fig. 6).
Coat new piston boot with clean brake fluid leav-
ing a generous amount inside boot. Position dust boot over piston after coating with
brake fluid. Install piston into caliper bore pushing it past the
piston seal until it bottoms in the caliper bore (Fig.
7).
CAUTION: Force must be applied to the piston uni-
formly to avoid cocking and binding of the piston in
the bore of the caliper.
Position dust boot in counterbore of the caliper pis-
ton bore. Using a hammer and Installer Piston Caliper Boot,
Special Tool C-4383-7 and Handle, Special Tool
C-4171, drive boot into counterbore of the caliper
(Fig. 8).
Fig. 5 Honing Piston Bore
Fig. 6 Installing New Piston Seal
Fig. 7 Pushing Piston into Bore
Fig. 8 Installing Boot in Caliper
5 - 50 BRAKES Ä

Use the following steps, to install the Guide Pin
Sleeve Bushings into the caliper assembly. (1) Fold the bushing in half lengthwise at the solid
middle section of the bushing (Fig. 9).
(2) Using your fingers insert the folded bushing into
the caliper assembly (Fig. 10). Do not use a sharp
object to perform this step do to possible damage
to the bushing.
(3) Unfold the bushing using your fingers or a
wooden dowel until the bushing is fully seated into the
caliper assembly. Flanges should be seated evenly on
both sides of the bushing hole in the caliper assembly
(Fig. 11). Install the Guide Pin Sleeve into the guide bushing
using the following procedure. (1) Install the sleeve into one end of the bushing
until the seal area of the bushing is past the seal
groove in the sleeve (Fig. 12).
(2) Holding the convoluted end of the bushing with
one hand. Push the sleeve through the bushing (Fig.
13) until the one end of the bushing is fully seated
into the seal groove on the one end of the sleeve. (3) Holding the sleeve in place work the other end
of the bushing over the end of the sleeve and into the
Fig. 11 Bushing Correctly Installed In Caliper
Fig. 12 Installing Caliper Sleeves
Fig. 9 Folded Caliper Guide Pin Bushing
Fig. 10 Installing Caliper Guide Pin Sleeve Bushings
Ä BRAKES 5 - 51

seal grove (Fig. 13). Be sure the other end of the
bushing did not come out of the seal grove in the sleeve.(4) When the sleeve is seated properly into the
bushing. The sealed for life bushing can be held be-
tween your fingers and easily slid back and forth
without the bushing seal unseating from the sleeve. Before installing caliper assembly on vehicle, inspect
braking disc. If any conditions as described in Check-
ing Braking Disc for Runout and Thickness are present
the braking disc, must be replaced or refaced. If the
braking disc does not require any servicing, install
caliper assembly. Install brake hose onto caliper using banjo bolt.
Torque the brake hose to caliper assembly banjo bolt to
33 N Im (24 ft. lbs.). New seal washers MUST al-
ways be used when installing brake hose to cali-
per. Bleed the brake system (see Bleeding Brake System).
Pump the brake pedal several times to be sure that the
vehicle has a firm pedal, before the vehicle is moved or
driven.
Fig. 13 Installed Caliper Bushing Sleeve
5 - 52 BRAKES Ä

BRAKE DISC (ROTOR) INDEX
page page
Braking Disc Removal ..................... 54
General Information ....................... 53
Inspection Diagnosis ...................... 53 Installing Braking Disc
..................... 54
Refinishing Braking Disc ................... 55
Service Procedures ....................... 53
GENERAL INFORMATION
Any servicing of the braking disc requires extreme
care to maintain the braking disc within service toler-
ances to ensure proper brake action.
CAUTION: If the braking disk (rotor) needs to be
replaced with a new part. The protective coating on
the braking surfaces of the rotor MUST BE REMOVED
with an appropriate solvent, to avoid contamination
of the brake shoe linings.
When replacing a rotor with a new part do NOT
reface the new rotor. Rotor already has the re-
quired micro finish when manufactured, only
remove the protective coating.
INSPECTION DIAGNOSIS
Before refinishing or refacing a braking disc, the disc
should be checked and inspected for the following
conditions: Braking surface scoring, rust, impregnation of lining
material and worn ridges. Excessive lateral rotor runout or wobble.
Thickness variation (Parallelism).
Dishing or distortion (Flatness).
If a vehicle has not been driven for a period of time.
The discs will rust in the area not covered by the brake
lining and cause noise and chatter when the brakes are
applied. Excessive wear and scoring of the disc can cause
temporary improper lining contact if ridges are not
removed before installation of new brake shoe assem-
blies. Some discoloration or wear of the disc surface is
normal and does not require resurfacing when linings
are replaced. Excessive runout or wobble in a disc can increase
pedal travel due to piston knock back. This will in-
crease guide pin bushing wear due to tendency of
caliper to follow disc wobble. Thickness variation in a disc can also result in pedal
pulsation, chatter and surge due to variation in brake
output. This can also be caused by excessive runout in
braking disc or hub. Dishing or distortion can be caused by extreme heat
and abuse of the brakes.
SERVICE PROCEDURES
CHECKING BRAKING DISC FOR RUNOUT AND THICKNESS
On vehicle, braking disc (rotor) runout is the com-
bination of the individual runout of the hub face and
the runout of the disc. (The hub and disc are separa-
ble). To measure runout on the vehicle, remove the
wheel and reinstall the lug nuts tightening the disc
to the hub. Mount Dial Indicator, Special Tool
C-3339 with Mounting Adaptor, Special Tool SP-1910
on steering arm. Dial indicator plunger should con-
tact disc (braking surface) approximately one inch
from edge of disc (See Fig. 1). Check lateral runout
(both sides of disc) runout should not exceed 0.13 mm
(0.005 inch).
If runout is in excess of the specification, check the
lateral runout of the hub face. Before removing disc
from hub, make a chalk mark across both the disc
and one wheel stud on the high side of runout. So
you'll know exactly how the disc and hub was origi-
nally mounted (Fig. 2). Remove disc from hub. Install Dial Indicator, Special Tool C-3339 and
Mounting Adaptor, Special Tool SP-1910 on steering
Fig. 1 Checking Braking Disc for Runout
Ä BRAKES 5 - 53

knuckle. Position stem so it contacts hub face near
outer diameter. Care must be taken to position stem
outside the stud circle but inside the chamfer on the
hub rim. Clean hub surface before checking. (See
Fig. 3)
Runout should not exceed 0.08 mm (0.003 inch). If
runout exceeds this specification, hub must be re-
placed. See Suspension Group 2. If hub runout does
not exceed this specification, install disc on hub with
chalk marks two wheel studs apart (Fig. 4). Tighten
nuts in the proper sequence and torque to specifica-
tions. Finally, check runout of disc to see if runout is
now within specifications. If runout is not within specifications. Install a new
braking disc or reface disc, being careful to remove
as little as possible from each side of disc. Remove
equal amounts from each side of disc. Do not reduce
thickness below minimum thickness cast into the un-
machined surface of the rotor. Thickness variation measurements of disc should
be made in conjunction with runout. Measure thick-
ness of disc at 12 equal points with a micrometer at
a radius approximately 25.4 mm (1 inch) from edge
of disc (Fig. 5). If thickness measurements vary by
more than 0.013 mm (0.0005 inch) disc should be re-
moved and resurfaced (Figs. 6 and 7), or a new disc
installed. If cracks or burned spots are evident in the
disc, disc must be replaced. Light scoring and/or wear is acceptable. If heavy
scoring or warping is evident, the disc must be refin-
ished or replaced (See Refinishing/Refacing Braking
Disc). If cracks are evident in the disc, replace the
disc.
BRAKING DISC REMOVAL
(1) Raise vehicle on hoist or jackstands. Remove
wheel and tire assembly. (2) Remove caliper assembly, as described under
Brake Shoe Removal in this Group, (but do not dis-
connect brake line). Suspend caliper from wire hook
or loop to avoid strain on flexible hose. (3) Remove braking disc from the hub.
INSTALLING BRAKING DISC
(1) Slide braking disc on hub. Clean both sides of
braking disc with alcohol or suitable solvent. (2) Install caliper assembly, as described in Brake
Shoe Installation paragraph.
Fig. 2 Marking Braking Disc and Wheel Stud
Fig. 3 Checking Hub for Runout
Fig. 4 Index Braking Disc and Wheel Stud
5 - 54 BRAKES Ä

REFINISHING BRAKING DISC
REFACING BRAKING DISC
Refacing of the braking disc is not required each
time the shoe assemblies are replaced. If the braking disc surface is deeply scored or
warped or there is a complaint of brake roughness or
pulsation the rotor should be resurfaced or refaced
(Figs. 6 and 7). When refacing a braking disc the required 0.10
mm (0.004 inch) TIR (Total Indicator Reading) and
0.013 mm (0.0005 inch) thickness variation limits
MUST BE MAINTAINED. Extreme carein the op-
eration of braking disc turning equipment is re-
quired. The collets, shafts and adapters used on the brake
lathe and the bearing cups in the rotor MUST be
clean and free from any chips or contamination. When mounting the disc on the brake lathe, strict
attention to the brake lathe manufacturer's operat-
ing instructions is required. If the disc is not mounted properly the run-out will
be worse after refacing than before refacing. The use of a double straddle cutter (Fig. 6) that
machines both sides of the disc at the same time is
highly recommended.
RESURFACING BRAKING DISC
This operation can be used when disc surface is
rusty, has lining deposits or excessive runout or
thickness variation is evident. A sanding disc attachment will remove surface con-
tamination without removing much braking disc ma-
terial. It will generally follow variations in thickness that
are in the disc. The following chart shows the location of measure-
ments and specifications when servicing the braking
disc. All braking discs have markings for minimum
allowable thickness cast on an un-machined sur-
face of the braking disc (Fig. 8). The thickness
Fig. 5 Checking Disc for Thickness
Fig. 6 Refacing Braking Disc
Fig. 7 Resurfacing Braking Disc (Final Finish)
Ä BRAKES 5 - 55