1993 DODGE TRUCK brake fluid

i - 12
BRAKES

•
Fig.
6 integral Cylinder
Components

Cylinder Cleaning And Inspection Clean the cylinder body and cover with brake fluid
or brake cleaner only. Do not use any other type of solvents, or cleaning agent. Inspect the cylinder body and bore. Light discolor­
ation of the cylinder bore is normal and is an accept­
able condition. The bore should be smooth and free of
scores, scratches, corrosion and rust. Replace the cyl­
inder if the bore is worn, scored, or corroded.
Do not hone the bore in an attempt to restore the
surface finish. Replace the cylinder if the bore is
damaged in any way. Also replace the cylinder if the
body is cracked, porous, or the compensator port at
the bottom of each reservoir is blocked or damaged.
Inspect the cover and gasket. Replace the gasket if
distorted, cut, or torn. Replace the cover and retain­
ing wire if either component is distorted or damaged
in any way.
Do not reuse the old piston assemblies. Discard
these parts as soon as they are removed. Install re­
placement primary and secondary piston assemblies
only.

INTEGRAL
CYLINDER ASSEMBLY
(1) Coat cylinder bore and replacement piston as­
semblies with liberal quantity of clean brake fluid.
(2) Install secondary piston assembly in bore with
a turning motion. Do not use metal tools of any kind
to help ease piston into bore. Sharp edge tools will
scratch bore and cut piston seals.
(3) If cylinder is equipped with stop screw for sec­
ondary piston, press piston to bottom of bore and in­
stall screw.
(4) Install primary piston in bore.
(5) Press pistons inward with wood dowel and in­
stall piston snap ring. Be sure snap ring is fully
seated.
(6) Install new gasket on cover if necessary.
(7) Install cover retaining wire on cylinder if re­
moved. (8) Fill and bleed master cylinder on bench before
installing it in vehicle. Refer to following procedure.
BLEEDING
NEW
OR
OVERHAULED MASTER

CYLINDER
A new or overhauled master cylinder should be
purged of all air before installation on the vehicle. Cylinder bleeding is performed on the bench. Bleeding tools for the integral master cylinder in­
clude fabricated bleed tubes and a wood dowel.
Bleeding tools for the two-section master cylinder in­ clude bleed tubes C-4029 and a wood dowel (Fig. 7).

CYLINDER BLEEDING PROCEDURE
(1) Mount master cylinder assembly in vise.
(2) Attach bleed tubes to cylinder outlet ports and
insert tubes in reservoir fluid compartments (Fig. 7).
Bleed tubes can be fabricated from steel or copper
tubing and appropriate size fittings.
(3) Fill reservoir with fresh brake fluid. (4) Press cylinder pistons inward with wood dowel.
Then release pistons and allow them to return under spring pressure.
(5) Continue bleeding operations until air bubbles
are no longer visible in fluid.

Fig.
7 Master Cylinder
Bleeding—
Two-Section
Cylinder
Shown

MASTER
CYLINDER INSTALLATION
(1) Bleed master cylinder on bench before installa­
tion. (2) Position master cylinder on studs of power
brake unit. (3) Align power brake push rod with master cylin­
der piston. (4) Install and tighten cylinder attaching nuts to
23 N-m (200 in. lbs.). (5) Connect front and rear brakelines to cylinder.
Start brakeline fittings by hand. (6) Tighten brakeline fittings to 19 N«m (170 in.

lbs.).
(7) Bleed brakes.

•

BRAKES
5 - 13
COMBINATION VALVE OPERATION

METERING (HOLD-OFF) VALVE The metering valve is used to balance brake action
between the front disc and rear drum brakes. The
valve meters (holds-off) full apply pressure to the front disc brakes until the rear brakeshoes are in full
contact with the drums.
The valve is designed to maintain front brake fluid
pressure at 3-30 psi until the hold-off limit of 117 psi is reached. At this point, the metering valve opens completely permitting full fluid apply pressure to the
front disc brakes.
PRESSURE DIFFERENTIAL SWITCH AND VALVE The pressure differential switch is connected to the
brake warning light. The switch is triggered by movement of the switch valve. The purpose of the switch is to monitor fluid pressure in the separate
front/rear brake hydraulic circuits.
A decrease or loss of fluid pressure in either hy­
draulic circuit will cause the switch valve to shuttle
forward or rearward in response to a pressure differ­ ential.
Movement of the switch valve will push the switch
plunger upward. This closes the switch internal con­ tacts completing the electrical circuit to the warning light. The switch valve will remain in an actuated
position until repair restores system pressures to nor­ mal levels.

COMBINATION VALVE TESTING
TESTING METERING VALVE Metering valve operation can be checked visually
and with the aid of a helper.
Observe the metering valve stem while a helper
applies and releases the brakes. If the valve is oper­
ating correctly, the stem will extend slightly when
the brakes are applied and retract when the brakes are released.
If the valve is faulty, replace the entire combina­
tion valve as an assembly.
TESTING PRESSURE DIFFERENTIAL SWITCH (1) Have helper sit in drivers seat to observe brake
warning light and to operate brake pedal.
(2) Raise vehicle on hoist.
(3) Connect bleed hose to left or right rear wheel
cylinder. Then immerse hose end in glass jar par­
tially filled with brake fluid.
(4) Have helper press and hold brake pedal all the
way down and observe warning light.
(a) If warning light illuminates, switch is operat­
ing correctly. (b) If light fails to illuminate, check circuit fuse,
bulb and wiring. Repair as necessary and repeat test steps (3) and (4). (5) If warning light still fails to illuminate, check
brakelight and park brake switches (and wiring) with test lamp. Repair or replace parts as necessary and test differential pressure switch operation again.
(6) If warning light still does not illuminate,
switch is faulty. Replace combination valve, bleed
brakes and verify proper switch and valve operation.

COMBINATION VALVE REMOVAL/INSTALLATION
VALVE REMOVAL (1) Raise vehicle on hoist.
(2) Mark or tag brake lines connected to valve for
assembly reference.
(3) Disconnect lines at valve (Fig. 8).
(4) Disconnect wires from differential pressure
switch.
(5) Remove bolts attaching valve to frame bracket
and remove valve.
VALVE INSTALLATION (1) Mount new valve on bracket and tighten valve
and bracket screws/nuts securely.
(2) Connect brakelines to valve. Tighten fittings to
16 N*m (145 in. lbs.)
(3) Connect wires to pressure differential switch
terminal. (4) Bleed brakes.
(5) Lower vehicle and verify proper brake opera­
tion.

BRAKE
LINES AND
HOSES

BRAKE LINE AND HOSE INSPECTION Flexible rubber hose is used at both front brakes
and at the rear axle junction block. Inspect the hoses
whenever the brake system is serviced, at every en­ gine oil change, or whenever the vehicle is in for ser­

vice.

Inspect the hoses for surface cracking, scuffing, or
worn spots. Replace any brake hose immediately if
the fabric casing of the hose is exposed by cracks or abrasion.
Also check brake hose installation. Faulty installa­
tion can result in kinked, twisted hoses, or contact with the wheels and tires or other chassis compo­
nents.
All of these conditions can lead to scuffing,
cracking and eventual failure.
The steel brake lines should be inspected periodi­
cally for evidence of corrosion, twists, kinks, leaks, or
other damage. Heavily corroded lines will eventually
rust through causing leaks. In any case, corroded or damaged brake lines should be replaced.

5
- 26
BRAKES

Fig. 13 Positioning Gasket On Pump Mounting
Flange
(2) Insert pump assembly upper attaching bolt in
mounting flange and gasket. Use sealer or grease to
hold bolt in place if necessary.
(3) Position pump assembly on engine and install
upper bolt (Fig. 14). Tighten upper bolt only enough
to hold assembly in place at this time. •
Fig. 14 Installing Pump Assembly On Engine (4) Working from under vehicle, install pump as­
sembly lower attaching bolt. Then tighten upper and
lower bolt to 77 N»m (57 ft. lbs.) torque. (5) Position bracket on steering pump inboard
stud. Then install remaining adapter attaching nut
on stud. Tighten nut to 24 N«m (18 ft. lbs.) torque.
(6) Connect oil feed line to vacuum pump connec­
tor. Tighten line fitting securely.
(7) Install oil pressure sender and connect sender

wires.
(8) Connect steering pump pressure and return
lines to pump. Tighten pressure line fitting to 30
N-m (22 ft. lbs.) torque.
(9) Connect vacuum hose to vacuum pump.
(10) Connect battery cables, if removed.
(11) Fill power steering pump reservoir.
(12) Purge air from steering pump lines. Start en­
gine and slowly turn steering wheel left and right to circulate fluid and purge air from system.
(13) Stop engine and top off power steering reser­
voir fluid level.
(14) Start engine and check brake and steering op­
eration. Verify that power brake booster is providing
vacuum assist and firm brake pedal is obtained.
Then verify that steering action is correct. Do this
before moving vehicle.
(4) Clean and lubricate pump shaft with engine

oil.
(5) Install spacers on steering pump studs (Fig.

12).
(6) Install O-ring on adapter (Fig. 11).
(7) Position adapter on pump studs.
(8) Install attaching nuts on outboard stud and on
the two upper pump studs. Do not install nut on
lower, inboard stud at this time. Tighten nuts to 24
N-m (18 ft. lbs.) torque. (9) Install coupling on pump shaft. Be sure cou­
pling is securely engaged in shaft drive tangs. (10) Install vacuum pump on adapter. Rotate drive
gear until tangs on pump shaft engage in coupling.
Verify that pump is seated before installing attach­
ing nuts. (11) Install and tighten vacuum pump attaching

nuts.

VACUUM-STEERING PUMP ASSEMBLY INSTALLATION

(1) Position new gasket on vacuum pump mount­
ing flange (Fig. 13). Use Mopar perfect seal, or sili­
cone adhesive/sealer to hold gasket in place.

•

BRAKES
5 - 27 CHRYSLER
DISC
BRAKE

INDEX

page
Caliper
Installation
. 33

Caliper Overhaul
32

Caliper Removal
31
Disc
Brake Inspection
29

Disc
Brakeshoe
Installation
, 31

GENERAL
INFORMATION

DISC BRAKE COMPONENTS The Chrysler disc brake consists of a sliding type,
single piston caliper and a ventilated disc brake rotor
(Figs.
1 and 2).
Each caliper is mounted on an adapter attached to
the steering knuckle (Fig. 2). Each- caliper slide lat­ erally on surfaces machined on the caliper and
mounting adapter. The adapters support the caliper and maintain fore and aft alignment of the caliper
and brakeshoes. Two retainer clips are used to main­
tain caliper alignment but permit lateral movement needed for caliper operation.
Non-metallic caliper pistons are used for all applica­

tions.
The pistons are made of a phenolic resin material.
Ventilated, cast iron disc brake rotors are used for all
applications. The rotors are serviceable and can be ma­
chined to restore surface finish when necessary. RETAINER CLIP

SPLASH

SHIELD RK71
Fig. 1 Chrysler Disc Brake Caliper Mounting—Rear View
page

Disc
Brakeshoe Removal
29

General
Information
....................... 27

Rotor Inspection
and
Service
................ 34

Rotor
Installation
. 35

Rotor Removal
34
SHIELD
RK72

Fig. 2 Chrysler Disc Brake Caliper Mounting—Front View The outboard brake shoe has flanges that locate
and position the shoe on the caliper fingers (Fig. 3).
Braking force on this shoe is taken by the caliper.
The inboard shoe is held in position by the adapter and reacts directly on the adapter.
The caliper is a one-piece casting with the inboard
side containing the single piston cylinder bore (Fig.

3).
A square cut piston seal is located in a machined
groove in the cylinder bore. A rubber dust boot is used to prevent dirt, water, road splash from enter­
ing the caliper piston bore. The boot is located in a
counterbore machined into the outboard end of the
caliper piston bore.
DISC BRAKE OPERATION The significant feature of caliper operation is that the
caliper is free to move laterally on the slide surfaces. 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 to press 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

•

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-