brakes DODGE TRUCK 1993 Service Service Manual

•

BRAKES
5 - 29 presses the outboard shoe lining against the opposite
side of the rotor to complete braking action.
The application or release of fluid pressure causes
only a very slight movement of the caliper and pis­
ton. At brake release, the piston and caliper return
to the non-applied position.
The brakeshoes do not retract an appreciable dis­
tance from the rotor. The minimal running clearance
between the lining and rotor provides improved re­ sponse and reduced pedal travel. It also helps in pre­
venting dirt and foreign material from lodging
between the shoe and rotor surfaces.

DISC
BRAKE
LINING WEAR COMPENSATION
Normal lining wear is compensated for by extension
of the caliper piston and by lateral movement of the cal­
iper in the adapter. Piston position is also determined
in part by the square cut piston seal (Fig. 4).
Normal disc brake lining wear will cause the cali­
per piston to extend enough to maintain proper pedal height and brake response. The caliper bore will re­ceive the extra fluid needed to compensate for the ad­
ditional piston extension.
As the piston extends during brake application, the
square-cut seal is deflected outward (Fig. 4). When
brake pressure is released, the seal straightens and
returns to a normal relaxed position. Although the amount of seal movement is quite small, it is enough
to retract the piston to the necessary minimum run­
ning clearance.
As lining wear occurs, the fluid level in the front
brake reservoir will decrease. This is a normal con­ dition and only requires adding enough fluid to re­store proper level. However, when the brakeshoes are
replaced and the caliper pistons bottomed in the

bores,
the added fluid must be compensated for to avoid overfill and overflow. Removing a small
amount of fluid from the front brake reservoir before­
hand will prevent this condition.
PISTON CALIPER
DUST BOOT
RN102

Fig.
4 Caliper
Piston
Seal
Operation

DISC
BRAKE INSPECTION
Inspect the disc brake components whenever the
caliper and brakeshoes are removed during service
operations or routine maintenance. Check condition of the rotor, brakeshoe lining, caliper
and brake hoses. Front wheel bearing adjustment and
condition can also be checked at this time. The bearings
should be repacked and adjusted if necessary.

Brakeshoes
With the caliper and brakeshoes on the vehicle,
check running clearance between the rotor and
brakeshoes. The shoe lining should either be in very light contact with the rotor or have a maximum of
0.127 mm (0.005 in.) running clearance. If clearance
exceeds the stated amount, apply the brakes several
times and recheck clearance. If clearance is still ex­ cessive, either the shoes are severely worn or the cal­
iper piston could be binding in the bore.

Hoses
And Adapter Inspect condition of the brake lines and hoses. Re­
place either front hose if cut, torn, or the reinforcing
fabric is visible. Check condition of the metal brake-
lines.
Replace any line that is badly rusted, leaking
or damaged in any way.
Clean and lubricate the slide surfaces of the caliper
and adapter. Use Mopar high temperature grease for
this purpose. Also verify that the caliper adapter
bolts are secure and tightened to proper torque.
Fluid Level Check the master cylinder fluid level. Maintain
fluid level to the bottom of the indicator rings on the
reservoir. Note that front disc brake fluid level can
be expected to drop slightly as normal lining wear occurs. Use Mopar brake fluid or equivalent meeting SAE and DOT standards J1703 and DOT 3. Use
clean brake fluid from a sealed container only.

Rotors
Check the rotor surfaces for excessive wear, discol­
oration, scoring, rust, scale, or cracks. Also look for
damaged or severely rusted ventilating segments. If
pedal pulsation was experienced, check wheel bear­ ing adjustment and condition. If the bearings are OK, also check rotor runout and thickness variation.

DISC
BRAKESHOE
REMOVAL
(1) If front brakeshoes are to be replaced, remove
approximately 1/3 of fluid from master cylinder front
brake reservoir with suction gun. (2) Raise and support vehicle.
(3) Remove front wheels.
(4) Press caliper pistons to bottom of bore with
large C-clamp. Position clamp screw on outboard
brakeshoe and position clamp frame on rear of cali­
per. (5) Remove bolts securing caliper retainer clips to
caliper. Then remove clips and anti-rattle springs (Fig. 5).

5 - 31
BRAKES

Fig.
5 Removing/installing Retainer Clips and Anti-Rattle Springs (6) Remove caliper by tilting it rearward and lift­
ing up and off rotor (Fig. 6).

Fig.
6 Caliper Removal/Installation
(7) Remove outboard brakeshoe from caliper (Fig.

7).
Use pry tool to remove shoe from caliper if
flanges are tight,
(8) Remove inboard brakeshoe from caliper mount­
ing adapter (Fig. 8). (9) Support caliper on box, stool, or front control
arm. Do not allow brake hose to support weight
of caliper. This practice could damage hose.
(10) Remove O-ring from caliper adapter. •

Fig.
7
Removing
Outboard
Brakeshoe
Fig.
8 Removing/Installing Inboard
Brakeshoe

CLEANING
AND
INSPECTION
Replace bonded disc brakeshoes if the lining is
worn to a thickness of 4 mm (3/16 in.) or less. Re­
place riveted shoes if the lining is worn to within 1.5
mm (1/16 in.) of the rivet heads.
If shoe replacement is necessary, replace the shoes
on both sides at the same time. Do not replace the shoes on one side only. This practice could result in
unequal braking effort and brake pull. Note that it is
normal for the inboard shoe lining to exhibit slightly more wear than the outboard shoe lining. Check for piston seal leaks which will be evident
by brake fluid in and around the boot area and in-

•

BRAKES
5 - 31 board lining. Also check condition of the caliper pis­
ton dust boot. If leakage is evident or if the boot is
cut, torn, or damaged in any way, it will be neces­sary to overhaul the caliper.
Remove the O-ring from the caliper adapter and clean
the slide surfaces of the adapter and the machined ways on the caliper with a wire brush and sandpaper.

DISC
BRAKESHOE
INSTALLATION
(1) Install inboard brakeshoe in adapter (Fig. 8).
(2) If new brakeshoes are being installed, remove
protective paper from noise suppression gasket on outboard shoe. (3) Install and adjust outboard brakeshoe in cali­
per as follows: (a) Check vertical movement of outboard shoe in
caliper. Shoe should fit tightly and not exhibit ver­
tical movement (free play). Flange must also fit
tightly on caliper finger to eliminate free play and
prevent shoe rattle (Fig. 9). (b) If free play is evident, remove shoe from cal­
iper. (c) Bend shoe retaining flange and trial fit shoe
in caliper. Continue bending flange until shoe is
light interference fit in caliper (Fig. 10). (d) Reinstall outboard brakeshoe in caliper. If
shoe is difficult to install, use C-clamp to seat shoe
(Fig. 11).

OUTBOARD SHOE MACHINED
Fig.
9 Outboard
Brakeshoe
Positioned
On Caliper
Finger

(4) Lubricate slide surfaces of caliper mounting
adapter and machined ways on caliper with Mopar
high temperature, or multi-mileage grease.
(5) Install O-ring in adapter, if removed.
(6) Carefully install caliper over rotor and into
adapter. Do not displace or damage the piston dust boot when installing the caliper.
Fig. 10
Adjusting Outboard
Brakeshoe
Retaining

Flange
Fig.
11 Seating Outboard
Brakeshoe

(7) Align caliper in adapter and install caliper re­
tainer clips and anti-rattle springs (Fig. 5). Tighten
retainer screws to 20 N«m (180 in. lbs.) torque.
(8) Install wheels and lower vehicle.
(9) Top off master cylinder fluid level. (10) Apply brakes several times to seat caliper pis­
tons and brakeshoes and obtain firm pedal. Do this
before moving vehicle.

CALIPER
REMOVAL
(1) Raise vehicle and remove front wheels.
(2) If caliper will only be removed for shoe replace­
ment or access to other component, press caliper pis­
ton to bottom of bore with large C-clamp. (3) Remove caliper retainer clips and anti-rattle
springs. (4) Disconnect brake hose fitting at caliper. (5) Remove caliper from rotor.
(6) Remove brakeshoes from caliper and adapter.

5
- 32
BRAKES

•
CALIPER
OVERHAUL

CALIPER DISASSEMBLY (1) Drain
old
fluid
out of
caliper.
(2)
Pad
outboard shoe side
of
caliper interior with
a minimum
2.54 cm (1 in.)
thickness
of
shop towels (Fig.
12).
Towels will prevent piston damage when
piston comes
out of
bore.
(3) Remove caliper piston with short bursts
of
com­
pressed
air.
Apply
air
pressure through fluid inlet
port
of
caliper
(Fig. 12).

CAUTION:
Do
not
blow
the
piston
out of the
caliper.

This
practice
will
usually
result
in
severe piston
damage.
Use
only enough
air
pressure
to
ease
the
piston
out of the
bore.
In
addition,
do not
attempt
to

catch
the
piston
as it
leaves
the
caliper
bore. This
practice
will
result
in
personal
injury.
Fig.
12
Caliper Piston Removal
(4) Remove piston dust boot. Collapse boot with
screwdriver
or
punch
and
remove boot
(Fig. 13).

(5) Remove caliper piston seal with wood pencil
or

plastic tool
(Fig. 14). Do not use
metal tools
as
they could scratch piston bore.
CLEANING
AND
INSPECTION Clean
the
caliper components
(Fig. 15)
with Mopar
brake cleaner, fresh brake fluid,
or
denatured alcohol only.
Do not use
gasoline, kerosene, thinner,
or any
similar type
of
solvent. These products
can
leave
a

residue that
is
damaging
to
pistons
and
seals. Dry
the
caliper
and
piston with compressed
air or

allow them
to air dry. Do not use
rags
or
shop tow­

els.
Lint from such materials
can
adhere
to the
cali­
per
and
piston. Fig. 14 Removing Caliper Piston Seal
Inspect
the
caliper piston.
The
piston
is
made from
a phenolic resin (plastic material)
and
should
be

smooth
and
clean. Replace
the
piston
if
cracked
or
scored.
Do not
attempt
to
restore
a
scored piston
by

sanding
or
polishing.
The
piston must
be
replaced
if

damaged.
If
the
caliper piston must
be
replaced, install
the same
type
of
piston
in the
caliper.
Never
in­

terchange phenolic resin
and
steel
pistons.
The
piston seals,
seal
grooves,
caliper bore
and pis-

•

BRAKES

5
- 33

BLEEDER
CALIPER
INBOARD
ANTI-RATTLE

PISTON
SPRING
RH242A
Fig.
15
Caliper Components ton tolerances
are
different
for
resin
and
steel
pistons
and
calipers.
Do not
intermix these com­
ponents
at any
time. Inspect
the
caliper piston bore.
The
bore
can be

lightly polished with Honing Tool C-4095
to
remove
very minor surface imperfections
(Fig. 16).
How­
ever,
the
caliper must
be
replaced
if the
bore
is
severely corroded, rusted, scored,
or if
polishing
would increase bore diameter more than 0.025
mm (0.001
in.).

Fig. 16 Lightly Polishing Piston Bore With Tool
C-4095

CALIPER ASSEMBLY (1) Coat caliper piston bore,
new
piston seal
and

piston with brake fluid.
(2) Install
new
piston seal
in
caliper bore.
Be
sure
seal
is
fully seated
in
groove
(Fig. 17).
(3) Install
new
dust boot
on
caliper piston. Seat
boot
in
piston groove.
(4) Start caliper piston
in
bore with
a
rotating
mo­

tion. When piston
is
started
in
seal, push piston only
part
way
into bore
(Fig. 18).
Maintain uniform pres­ sure
on
piston
to
avoid cocking
it in
bore.
Fig.
17 Installing Caliper
Piston
Seal

Fig.
18 Installing Caliper
Piston

(5) Press caliper piston
to
bottom
of
bore
and
seat
piston dust boot with Installer C-4690
and
Tool Han­ dle C-4171
(Fig. 19).
(6) Install caliper bleed screw
if
removed.

CALIPER
INSTALLATION
(1) Clean slide surfaces
of
caliper mounting
adapter with wire brush. Then lubricate adapter
slide surfaces with Mopar multi-mileage,
or
high
temperature grease.
(2) Install inboard brakeshoe
in
adapter.
(3) Install outboard brakeshoe
in
caliper.
Be
sure
shoe
is
light press
fit in
caliper. Refer
to
installation
procedure
in
Brakeshoe Replacement section. (4) Lubricate caliper slide surfaces Mopar multi-
mileage,
or
high temperature grease. (5) Install O-ring
in
adapter,
if
removed.

5
- 34
BRAKES

•
boot
>TALLir TOOL
Fig.
19 Seating
Piston
Dust
Boot

(6) Install caliper over rotor and into adapter.
(7) Align caliper in adapter and install caliper re­
tainer clips and anti-rattle springs. Tighten retainer clip screws to 20 N*m (180 in. lbs.) torque.
(8) Connect brake hose to caliper. Tighten fitting
bolt to 47 N»m (35 ft. lbs.) torque. Be sure hose is clear of chassis and suspension components and
use new seal washers to secure hose fitting to caliper. Do not reuse old washers.
(9) Fill master cylinder with Mopar brake fluid or
equivalent meeting SAE and DOT standards J1703 and DOT 3.
(10) Bleed brakes. Refer to procedure in Service
And Adjustments section.
(11) Install wheels and lower vehicle.
(12) Apply brakes several times to seat caliper pis­
tons and brakeshoes. Be sure firm pedal is obtained
before moving vehicle.

ROTOR REMOVAL
(1) Raise and support vehicle.
(2) Remove wheel and tire assembly.
(3) Remove caliper assembly. Do not allow brake
hose to support caliper. Support caliper on stool, or suspend caliper with wire attached to nearby body or
suspension component. (4) Remove grease cap, cotter pin, nut lock, adjust­
ing nut, thrust washer and outer wheel bearing. (5) Remove rotor from spindle.
(6) Remove rotor shield and seal if either is to be
serviced.
ROTOR
INSPECTION AND
SERVICE

rotor condition The rotor braking surfaces should not be refinished
unless actually necessary. Light surface rust and scale can be removed in a lathe equipped with dual
sanding discs.
Rotor surfaces can be restored by machining in a
disc brake lathe if surface scoring and wear are light.
The rotor should be replaced if:
• severely scored
• tapered
• has hard spots
• is cracked
• too thin • machining would cause rotor thickness to fall be­
low minimum thickness requirements Check rotor lateral runout and thickness variation
if pedal pulsation or an occasional low pedal condi­
tion was experienced. Measure runout with a dial in­ dicator. Measure thickness with a micrometer at a
minimum of four points around the braking surfaces.

CHECKING
ROTOR
MINIMUM
THICKNESS
Measure rotor thickness at the center of the brake-
shoe contact surface. Replace the rotor if it is worn
below minimum thickness, or if refinishing would re­ duce thickness below the allowable minimum. Rotor
minimum thickness is usually specified on the rotor
hub (Fig. 20).
Fig.
20 Typical Location Of Rotor
Minimum

Thickness
Limit
ROTOR RUNOUT Check rotor lateral runout with Dial Indicator
C-3339 as shown in the top view (Fig. 21). Excessive

•

BRAKES
5 - 35 lateral runout will cause brake pedal pulsation and
rapid, uneven wear of the brakeshoes. Position the dial indicator plunger approximately
25.4
mm (1 in.)
from the rotor outer edge.
Be sure wheel bearing adjustment is correct
before checking rotor runout. Incorrect adjust­
ment can create a condition similar to excessive
lateral runout- Maximum allowable rotor runout for all models is

0.102
mm
(0.004
in.).
Fig. 21 Checking Rotor Runout And Thickness Variation

ROTOR
THICKNESS VARIATION Variations in rotor thickness will cause pedal pul­
sation, noise and shudder.
Measure rotor thickness at 6 to 12 points around
the rotor face (Fig. 21). Position the micrometer ap­
proximately 19,05 to
25.4
mm
(3/4
to 1 in.) from the rotor outer circumference for each measurement as
shown in the bottom view (Fig. 21).
Thickness should not vary by more than
0.013
mm

(0.0005
in.) from point-to-point on the rotor. Refinish
or replace the rotor if necessary.

ROTOR
REFINISHING Rotor braking surfaces can be refinished by sand­
ing and/or machining in a disc brake lathe. The lathe
must be capable of machining both rotor surfaces si­
multaneously with dual cutter heads (Fig. 22). A
brake lathe capable of machining only one side at a
time will produce a tapered rotor.
The disc brake lathe should also be equipped with
a grinder attachment, or dual sanding discs for final
cleanup or light refinishing (Fig. 22).
If the rotor surfaces only need minor cleanup of
rust, scale, or scoring, use abrasive discs to clean up
the rotor surfaces. However, when a rotor is scored or
worn, machining with cutting tools will be required.
CAUTION:
Do not
refinish
a
rotor
if
machining

would
cause
rotor
thickness
to
fall
below minimum
allowable.

Fig.
22 Rotor
Refinishing
Equipment

ROTOR
INSTALLATION
(1) Inspect and repack wheel bearings if necessary.
Install new grease seal if inner bearing is removed
for repacking.
(2)
Install rotor on spindle.

(3)
Install outer bearing, thrust washer and nut.

(4)
Tighten wheel bearing adjusting nut to
27-34

Nth
(240-300
in. lbs.) while turning rotor. (5) Recheck rotor runout as described previously.

5
- 36
BRAKES

• (6) Loosen wheel bearing adjusting nut completely.
Then retighten nut finger tight. Wheel bearing end
play should be maximum of 0.002 to 0.076 mm (0.0001 to 0.003 in.).
(7) Install nut lock on bearing adjusting nut. Align
lock slots with cotter pin hole and secure nut and
lock with new cotter pin. (8) Clean grease cap. Then coat interior of cap with wheel bearing grease.
(9) Install caliper, wheel and tire assembly and
lower vehicle.
(10) Check and adjust master cylinder fluid level.
(11) Apply brakes several times to seat brake-

shoes.
Be sure to obtain firm pedal before moving ve­
hicle.

•

BRAKES
5 - 37
BENDIX
DISC
BRAKE

INDEX

page
Caliper Overhaul
41
Disc
Brake Inspection
39

Disc
Brakeshoe
Installation
40
Disc
Brakeshoe Removal
. 39

GENERAL
SERVICE
INFORMATION
The Bendix disc brake assembly consists of a single
piston, sliding type caliper and ventilated rotor (Fig. 1). A splash shield is used to protect the rotor. The
shield is bolted to the adapter and protects the bear­
ings and inboard surface of the rotor from road splash. The wheel protects the outboard surface of
the rotor and brake assembly. The caliper slides laterally on surfaces machined
into the caliper and mounting adapter. The adapter
is bolted to the steering knuckle (Fig. 2). The caliper
is positioned in the adapter with a support key and spring (Fig. 1). A retaining screw is used to secure
the support key. The inboard brakeshoe is mounted in the caliper
adapter. The outboard brakeshoe is mounted in the
caliper. The linings are riveted to the shoes, and the
inner and outer shoes are not interchangeable.

DISC
BRAKE OPERATION
The significant feature of caliper operation is that
the caliper is free to move laterally on the adapter slide surfaces (Fig. 3).
Fig.
1
Bendix
Disc
Brake Caliper
page
General Service
Information
37
Rotor Inspection
and
Service
................ 43

Rotor
Installation
45

Rotor Removal
45

Fig.
2 Caliper
Mounting
Adapter Attachment
At brake application, fluid pressure is exerted
equally against the caliper piston and all surfaces of
the caliper piston bore.
Pressure applied to the piston is transmitted di­
rectly to the inboard brakeshoe pressing the shoe lin­ ing against the rotor. At the same time, pressure applied to the caliper bore surfaces, causes the cali­
per to slide inward laterally. The inward movement
presses the lining of the outboard shoe against the
opposite side of the rotor to complete braking action (Fig. 3).
Any application or release of brake fluid pressure
causes only a very modest movement of the caliper and piston. At brake release, the piston and caliper
return to the non-applied position.
The brakeshoes do not retract an appreciable dis­
tance from the rotor. The minimal running clearance
provides the improved response and reduced pedal
travel; It also helps in preventing dirt and foreign
material from lodging between the shoe and rotor surfaces.

BRAKES
5 - 39
DISC BRAKE LINING WEAR COMPENSATION
Normal lining wear is compensated for by exten­
sion of the caliper piston and by lateral movement of
the caliper in the adapter. Piston position is also de­ termined in part by the square cut piston seal (Fig.
4).

Normal disc brake lining wear will cause the cali­
per piston to extend enough to maintain proper pedal height and brake response. The caliper bore will re­ceive the extra fluid needed to compensate for the ad­
ditional piston extension.
As the piston extends during brake application, the
square-cut seal is deflected outward (Fig. 4). When
brake pressure is released, the seal straightens and returns to a normal relaxed position. Although the amount of seal movement is quite small, it is enough
to retract the piston to the necessary minimum run­ ning clearance. Fluid level in the front brake reservoir will de­
crease as lining wear occurs, the. This is a normal
condition and only requires adding enough fluid to
restore proper level. However, when the brakeshoes are replaced and the caliper pistons bottomed in the

bores,
the added fluid must be compensated for. This is necessary to avoid overfill and overflow. Removing a small amount of fluid from the front brake reser­
voir beforehand will prevent this condition.

Fig.
4 Caliper
Piston
Seal
Operation

DISC
BRAKE INSPECTION
Inspect the disc brake components whenever the
caliper and brakeshoes are removed during service
operations or routine maintenance. Check condition of the rotor, brakeshoe lining, cal­
iper and brake hoses. Front wheel bearing adjust­
ment and condition can also be checked at this time.
The bearings should be repacked and adjusted if nec­ essary.

Brakeshoes
With the caliper and brakeshoes on the vehicle,
check running clearance between the rotor and
brakeshoes. The shoe lining should either be in very light contact with the rotor or a maximum of 0.127
mm (0.005 in.) running clearance. If clearance ex­ceeds the stated amount, apply the brakes several times and recheck clearance. If clearance is still ex­
cessive, either the shoes are severely worn or the cal­
iper piston could be binding in the bore.

Hoses
And Adapter Inspect condition of the brake lines and hoses. Re­
place either front hose if cut, torn, or the reinforcing
fabric is visible. Check condition of the metal brake-
lines.
Replace any line that is badly rusted, leaking
or damaged in any way.
Clean and lubricate the adapter slide surfaces. Use
Mopar multi-mileage or high temperature grease for
this purpose. Also verify that the caliper adapter
bolts are secure and tightened to proper torque.
Fluid Level Check the master cylinder fluid level. Maintain
fluid level to the bottom of the indicator rings on the
reservoir. Note that front brake fluid level can be ex­
pected to drop slightly as normal lining wear occurs.
Use Mopar brake fluid or equivalent meeting SAE and DOT standards J1703 and DOT 3. Use clean
brake fluid from a sealed container only.

Rotors
Check rotor surfaces for excessive wear, discolora­
tion, scoring, rust, scale, or cracks. Also look for damaged or severely rusted ventilating segments. If
pedal pulsation was experienced, check wheel bear­ ing adjustment and condition. If the bearings are OK, also check rotor runout and thickness variation.

DISC
BRAKESHOE REMOVAL
(1) Remove approximately 1/3 of fluid from master
cylinder front brake reservoir with a suction gun. (2) Raise and support vehicle.
(3) Remove wheel and tire assemblies.
(4) Press caliper pistons to bottom of bore with
large C-clamp (Fig. 5). Position clamp screw on out­
board shoe and clamp frame or rear of caliper hous­ ing. (5) Remove support key retaining screw (Fig. 6).
(6) Remove caliper support key and spring. Use
pin punch or drift to tap key out of caliper (Fig. 7). (7) Lift caliper out of adapter. (8) Remove outboard shoe from caliper (Fig. 8).
(9) Secure caliper to convenient chassis component
with wire. Do not allow brake hose to support caliper weight. (10) Remove inboard shoe and anti-rattle spring
from caliper adapter (Fig. 9). Note position of spring
for installation reference.
CLEANING AND INSPECTION Inspect the shoe lining for wear. Replace riveted
shoes if the lining is worn to within 1.5 mm (1/16 in.)
of the rivet heads. Replace bonded lining if thickness is 3 mm (3/16 in.) or less.