1993 DODGE TRUCK Service Repair Manual

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.

5
- 40
BRAKES

•

Fig.
6 Removing/Installing
Support
Key Retaining
Screw
If the shoe lining will be reused, do not intermix
the shoes. Keep them with the caliper they were re­ moved from.
Examine the caliper piston area for evidence of

leaks.
Also check condition of the piston boot. Over­
haul the caliper if leakage is evident or the boot is
cut or torn.
Clean rust and corrosion from the support key and
the caliper and adapter slide surfaces (machined
ways) with a wire brush. Then lubricate the slide surfaces with Mopar multi-mileage grease, or equiv­
alent.

DISC
BRAKESHOE
INSTALLATION
(1) Install anti-rattle spring on inboard brakeshoe
and install shoe in adapter. Be sure spring remains
in place and is positioned as shown (Fig. 9). Loop
portion of spring should face away from the rotor.
BRASS
ROD



Fig.
7
Removing
Caliper
Support
Key And
Spring

Fig.
8 Removing/Installing Outboard
Brakeshoe
(2) Install outboard shoe in caliper. Free play
should not exist between shoe retaining flanges and
machined surfaces on caliper. If shoe cannot be
pressed into place by hand, use a C-Clamp. If a C-Clamp is used, protect shoe with wood block (Fig.
10).

(3) Position caliper over rotor and in adapter (Fig.

11).
Be careful to avoid damaging piston dust boot
during installation.

CAUTION:
Verify
that
the brake
hose
is straight

and
not twisted, kinked, or
touching
any
chassis
components.

•

BRAKES
5 - 41

Fig.
9 Removing/Installing Inboard
Brakeshoe

Fig.
10 Seating Outboard
Brakeshoe
In Caliper (4) Seat caliper in adapter.
(5) Place support spring on support key. Then in­
sert spring and key between caliper and adapter.
(6) Tap support key and spring into place with pin
punch or drift (Fig. 12). (7) Align notch in support key with screw hole in
caliper.
(8) Install support key retaining screw. Tighten
screw to 20 N»m (15 ft. lbs.) torque. Be sure shoul­
der on screw is fully seated in support key
notch.
(9) Install wheel and tire assembly and lower vehi­

cle.
(10) Top off master cylinder fluid level.
(11) Pump brake pedal to seat shoes and restore
normal pedal height. Do not move vehicle until firm
pedal is obtained.
CALIPER

Fig.
11 Caliper
Installation
CALIPER

Fig.
12 Installing
Support
Key And
Spring

CALIPER
OVERHAUL
CALIPER REMOVAL
(1) Raise vehicle and support on hoist or jack-
stands.
(2) Remove wheel and tire assemblies.
(3) Clean brake hose and tubing connections at
calipers and brake hoses.
(4) Remove screw retaining caliper support key
and spring and tap support key and spring out with
a drift or pin punch.
(5) Remove calipers and brakeshoes from adapters (6) Disconnect caliper brake hoses at frame brack­
ets and remove calipers. (7) Cover brake lines to prevent dirt entry.

5
- 42
BRAKES

•
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. 13). Towels will prevent piston damage when it
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. 13).

CAUTION:
Do not
blow
the
piston
out of the
cali­

per.
This
practice
will
usually
result
in
severe
pis­

ton
damage.
Use only
enough
air
pressure
to
ease

the
piston
out of the
bore.
In
addition,
do not at­

tempt
to catch the
piston
as it
leaves
the
caliper
bore.
This
practice
will
result
in
personal
injury.
PISTON
J9105-66

Fig.
13 Caliper
Piston
Removal (4) Remove dust boot from caliper.
(5) Remove caliper piston seal from caliper bore
with small wood or plastic tool. Do not use metal tools to remove seal. Metal tools can scratch or score bore surface. (6) Remove bleed screw from caliper.

CLEANING
AND INSPECTION Clean the slide surfaces of the caliper with a wire
brush and emery cloth. Then clean the caliper and
piston with Mopar brake cleaner, fresh brake fluid, or denatured alcohol only. Do not use any other type
of solvent or cleaning agent.
Dry the caliper and piston with compressed air or
allow them to air dry. Do not use rags or towels to
dry the caliper and piston. Lint from such materials
can adhere to the piston and caliper. Inspect the caliper piston, piston bore and the seal
and boot grooves. Replace the piston if corroded, pit­
ted, scored, or worn. Do not attempt to restore the
piston surface by sanding. Replace the piston if nec­ essary.
Very light scratches or corrosion in the piston bore
can usually be cleaned up with a fiber brush, or by
polishing with a honing tool or crocus cloth. How­ ever, the caliper should be replaced if the bore is se­
verely corroded, scored, or if honing and polishing
would increase bore diameter by more than 0.050
mm (0.002 in.).
Dark brown or black stains on the piston are
caused by the piston seal and are a normal condition.
In addition, light discoloration of the piston bore is also normal. This discoloration is acceptable as long as the bore and piston surfaces are in good condition.
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
ton tolerances are different for resin and steel
pistons and calipers. Do not intermix these com­ ponents at any time.
The caliper bore can be lightly polished to remove
minor scratches or corrosion. However, polishing op­
erations should not remove any more than 0.012 mm (0.0005 in.) from the bore surface. Replace the caliper
if the bore is severely scored or corroded. Use crocus
cloth or 400 grit honing stones soaked in fresh brake
fluid to polish the bore surface. Be sure to flush and
clean the caliper thoroughly afterward. All residue generated by polishing must be removed to avoid po­
tential damage to the piston, seal and bore after as­ sembly. Inspect and clean the inboard shoe anti-rattle
spring, support key spring, retaining screw and cali­
per support key (Fig. 14). Replace these components if worn or damaged.
SHOE
AND
SHOE
AND
CALIPER
BLEEDER
SCREW

SEAL
BOOT
ANTI-RATTLE
SPRING
RN1059
Fig.
14 Caliper
Components

•

BRAKES
5 - 43
CAMPER
ASSEMBLY
(1) Mount caliper in vise equipped with protective

jaws.
Do not overtighten vise. Excessive pressure could cause bore distortion and piston binding. (2) Lubricate new piston seal and piston bore with
fresh brake fluid. (3) Install new piston seal in bore groove (Fig. 15).
Position seal in one area of groove and gently work it around and into remainder of groove until seated. Be
sure seal is not twisted or rolled over.

Fig.
15 Installing Caliper
Piston
Seal

(4) Lubricate new dust boot with fresh brake fluid
and install it in caliper (Fig. 16). Work boot into
groove with fingers. Boot will seem larger than
groove diameter at first but will snap into place
when properly positioned.
(5) Plug fluid inlet port and install bleeder screw. (6) Coat caliper piston with brake fluid.
(7) Start piston into dust boot and bore (Fig. 16).
Spread dust boot with fingers. Then work piston
through boot and into bore. Air trapped below piston
will force boot around it and into groove as piston is installed.
(8) Remove plug from inlet port and loosen bleeder
screw.
(9) Carefully press piston into bore with turning
motion until fully bottomed. Apply force uniformly to avoid cocking piston (Fig. 16).
(10) Seat dust boot with suitable size installer tool
if necessary.

CALIPER
INSTALLATION
(1) Install brakeshoes in caliper and adapter.
Fig.
16 Installing Caliper
Piston

(2) Connect brake hose to brake line on frame
bracket. Tighten hose fitting to 13-20 N«m (115-175 in. lbs.) torque.
(3) Connect brake hose to caliper. Use new seal
washers when connecting fitting to caliper. Do not
tighten hose fitting at this time.
(4) Lubricate caliper and adapter slide surfaces
with Mopar high temperature grease, or an equiva­ lent grease.
(5) Install and secure caliper in adapter.
(6) Fill master cylinder and bleed brakes.
(7) Install wheel and tire assemblies and lower ve­
hicle.

ROTOR INSPECTION AND
SERVICE

ROTOR
CONDITION
Rotor condition and tolerances can be checked with
the rotor mounted on the axle. However, wheel bear­ ing end play should be reduced to zero before check­
ing lateral runout.
The rotor braking surfaces should not be machined
unless actually necessary. Light surface rust and scale can be removed in a lathe equipped with dual
sanding discs.
Worn, or scored rotor surfaces can be restored by
machining in a disc brake lathe but only if surface scoring and wear are light.
The rotor should be replaced if:
• severely scored
• tapered
• has hard spots
• cracked
• warped
• too thin
• machining would cause rotor thickness to fall be­
low minimum thickness requirements

5
- 44
BRAKES

• 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.
The rotor measurement points are shown in Figure
17.
Fig. 17 Rotor Measurement
Points
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.

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. 18). Position the micrometer ap­
proximately 25.4 mm (1 in.) from the rotor outer cir­ cumference for each measurement (Figs. 17 and 19). Thickness should not vary by more than 0.025 mm
(0.001 in.) from point-to-point on the rotor. Refinish
or replace the rotor if necessary.
ROTOR RUNOUT Check rotor lateral runout with Dial Indicator
C-3339 (Fig. 18). Excessive 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.) in from the rotor edge. Be sure
wheel bearing end play is reduced to zero before
checking runout. Maximum allowable runout is 0.127 mm (0.005 in.).
Fig. 18 Checking Rotor Runout And
Thickness
Variation

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-

•

BRAKES
5 - 45 multaneously with dual cutter heads. Equipment ca­
pable of machining only one side at a time will
produce a tapered rotor. The lathe should also be equipped with a grinder
attachment or dual sanding discs for final cleanup or
light refinishing.
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
the rotor to
fall
below minimum allow­
able
thickness.

ROTOR REMOVAL
(1) Raise and support front of vehicle.
(2) Remove wheel and tire assemblies.
(3) Remove support key retaining screw (Fig. 6).
(4) Remove caliper support key and spring with
pin punch or drift (Fig. 19).

Fig.
19
Removing
Caliper
Support
Key And
Spring
(5) Remove caliper and brakeshoes from adapter.
Do not allow brake hose to support caliper
weight. Support caliper on stool, or secure cali­
per to nearby frame or chassis component with
wire.
(6) Remove hub cap. (7) Remove drive flange snap ring with Tool
C-4020 (Fig. 20).
(8) Remove flange nuts and lock washers and re­
move drive flange. Discard the flange gasket.
(9) Straighten tang on lock ring. (10) Loosen outer locknut and adjusting nut with
Tool DD-1241-JD (Fig. 19). Then remove outer lock- nut, lock ring, inner adjusting nut and outer bearing. (11) Remove hub and rotor from spindle.
Fig.
20
Removing
Drive Flange
Snap
Ring

(12) Remove seal and inner bearing from hub if
bearing or seal requires service.
(13) If wheel bearing races require service, remove
them with suitable remover tools or with brass drift. (14) Clean rotor and hub and wheel bearings in
solvent.

ROTOR
INSTALLATION
(1) Repack wheel bearings and coat spindle with
Mopar high temperature bearing grease. (2) Install new bearing races, bearings and seals in
hubs if necessary. (3) Install hub on spindle and install outer bearing
and inner adjusting nut. (4) Tighten adjusting nut to 68 Nrni (50 ft. lbs.)
with Special Tools DD-1241-JD and C-3952 to seat
bearings. (5) Adjust wheel bearings as follows: (a) Back off adjusting nut.
(b) Retighten adjusting nut to 54 N*m (40 ft. lbs.)
while rotating hub and rotor. (c) Back off adjusting nut approximately 135 to
150 degrees. (d) Install lock ring and locknut.
(6) Tighten lock nut to a minimum of 88 N»m (65
ft. lbs.). Bearing end play should be 0.025 - 0.25 mm (0.001 - 0.010 in.). (7) Bend one tang of lock ring over adjusting nut
and another tang over locknut to secure them. (8) Install new gasket on hub and install drive
flange, lock washers and nuts. Tighten nuts to 41 - 54 N«m (30 - 40 ft. lbs.). (9) Install flange snap ring with Tool C-4020.
(10) Install hub cap.
(11) Install caliper and brakeshoes. Tighten sup­
port retaining screw to 20 Nnn (15 ft. lbs.) torque. (12) Install wheel and tire assembly and lower ve­
hicle.