1993 DODGE TRUCK brakes

5
- 20
BRAKES

•
POWER BRAKE BOOSTER—BRAKE PEDAL

INDEX

page
Brake Pedal
Installation
21

Brake Pedal Removal
21

General
Information
.......................
20
page
Power Brake Booster
Installation
.............
21

Power Brake Booster Removal
21

GENERAL
INFORMATION
Power brakes
are
standard
on all AD
models.
A

single
or
dual diaphragm, vacuum power brake
booster
is
used. AD
and W150
models
are
equipped with
a
single
diaphragm booster unit
(Fig. 1). D and
W250/350
models
are
equipped with
a
dual diaphragm booster. The booster unit consists
of a
single housing
di­

vided into separate chambers
by one or two
internal
diaphragms.
The
outer edge
of the
diaphragm
is se­

cured
to the
housing. The booster push
rod,
which connects
the
booster
to

the brake pedal
and
master cylinder,
is
attached
to

the center
of the
diaphragm.
A
check valve
is
used
in

the booster outlet connected
to the
engine intake manifold. Power assist
is
produced
by a
combination
of
vac­
uum
and
atmospheric pressure
to
boost brake assist. The power brake booster
is not a
repairable
component.
The
booster must
be
replaced
as an
assembly
if
diagnosis indicates
a
malfunction
has occurred.
AD models with
the
Cummins diesel engine
are

equipped with
a
dual diaphragm power brake
booster.
A
separate vacuum pump assembly supplies the vacuum needed
for
booster operation
(Fig. 2).

The diesel vacuum pump
and the
power steering
pump
are
combined into
a
single assembly. Both
pumps
are
operated
by a
drive gear pressed onto
the

vacuum pump shaft.
The
drive gear
is
operated
by

the camshaft gear. A suspended-type brake pedal
is
used
for all
appli­
cations.
The
pedal
is
attached
to the
pedal support
bracket with
a
pivot shaft.
The
pedal, bolt
and
bush­ ings
are all
serviceable components.
RESERVOIR
PEDAL
SHAFT

RETAINER
SCREW

MASTER
CYLINDER

AND BOOSTER
ASSEMBLY <5>

I
RETAINER
CLIP

TIGHTENING
TORQUE

'A>
200
IN.-LBS.
(23 N-m)

¥>
35
IN.-LBS.
(4 N.m)
LOCKNUT
«
RK721

Fig.
1
Power
Brake
Booster
And
Pedal
Mounting

•

BRAKES
5 - 21

VACUUM

GEAR
ADAPTER
J9105-94

Fig. 2
Diesel
Vacuum
And
Power
Steering
Pump
Assembly
POWER BRAKE BOOSTER REMOVAL

(1) Disconnect vacuum hoses from booster check
valve. (2) Remove nuts attaching master cylinder to
booster and move cylinder away from booster. (3) Inside vehicle, remove clip that secures booster
push rod to brake pedal (Fig. 1). Use screwdriver to ease clip off pedal pivot pin. (4) Remove locknuts from booster mounting studs.
(5) Slide booster away from dash and out of engine
compartment.
POWER BRAKE BOOSTER
INSTALLATION

(1) If new booster is not equipped with check valve
and seal, transfer these parts to new booster. (2) Align and position booster on dash panel.
(3) Install locknuts on booster mounting studs fin­
ger tight. (4) Install booster push rod on brake pedal pin and
secure the rod with a new retaining clip. (5) Tighten booster locknuts to 25 Nth (220 in.
lbs.) torque. (6) Install master cylinder on booster. Then install
and tighten cylinder mounting nuts to 19-23 Nnn
(170-200 in. lbs.) torque. (7) Connect vacuum hose to booster check valve.

BRAKE PEDAL REMOVAL
(1) Disconnect booster push rod from pedal. (2) Remove screw attaching pedal shaft to brake
support. (3) Pull pedal shaft out of support just enough to
remove brake pedal. (4) Slide pedal off shaft and remove it from vehi­

cle.
BRAKE PEDAL
INSTALLATION
(1) Lubricate pedal shaft and bore in brake pedal
with Mopar multi-mileage grease. (2) Position pedal on shaft. Then slide shaft
through pedal and into support. (3) Secure pedal shaft to support with retaining
screw. (4) Attach push rod to pedal.
(5) Verify correct pedal and brake operation before
moving vehicle.

5
- 22
BRAKES

POWER BRAKE
VACUUM
PUMP—DIESEL ENGINE

INDEX

page

General
Information
22
Low
Vacuum
Warning
Switch
22
Pump
Adapter
Replacement
. 25

Vacuum
Pump
Diagnosis
..................
23

Vacuum
Pump
Operation
..................
23
page

Vacuum
Pump
Replacement
24

Vacuum
Pump
Serviceability
22
Vacuum—Steering
Pump
Assembly
Installation
. . 26

Vacuum—Steering
Pump
Assembly
Removal
... 23

GENERAL
INFORMATION
The power brake booster vacuum pump
and the

power steering pump
are
combined into
a
single
as­
sembly
on
diesel models
(Fig. 1).
Both pumps
are op­

erated
by a
drive gear attached
to the
vacuum pump shaft. The vacuum pump
is a
constant displacement,
vane-type pump. Vacuum
is
generated
by
four vanes
mounted
in the
pump rotor.
The
rotor
is
located
in

the pump housing
and is
pressed onto
the
pump shaft. The vacuum
and
steering pumps
are
operated
by a

single drive gear pressed onto
the
vacuum pump
shaft.
The
drive gear
is
operated
by the
camshaft
gear. The vacuum
and
power steering pump shafts
are

connected
by a
coupling. Each pump shaft
has an
adapter with drive lugs that engage
in the
coupling. The vacuum pump rotating components
are
lubri­
cated
by
engine
oil.
Lubricating
oil is
supplied
to the

pump through
an oil
line
at the
underside
of the

pump housing. The complete assembly must
be
removed
in
order
to service either pump. However,
the
power steering
pump
can
removed
and
serviced separately when necessary.

VACUUM
PUMP
SERVICEABILITY
The vacuum pump
is not a
serviceable component.
If diagnosis indicates
a
pump malfunction,
the
pump must
be
replaced
as an
assembly.
Do not
disassemble
or attempt
to
repair
the
pump.
The combined vacuum
and
steering pump assembly
must
be
removed
for
access
to
either pump. However,
the vacuum pump
can be
removed without having
to
disassemble
the
power steering pump. If
the
power steering pump requires service, simply
remove
the
assembly
and
separate
the two
pumps. Refer
to the
pump removal
and
installation proce­dures
in
this section.

LOW
VACUUM
WARNING
SWITCH
A vacuum switch
is
used
to
monitor output
of the

vacuum pump.
The
switch
is in
circuit with
the
brake warning light.
VACUUM

PUMP

DRIVE

GEAR
PUMP

ADAPTER
POWER

STEERING
PUMP

J9105-94

Fig.
1
Diesel
Vacuum
And
Power
Steering
Pump
Assembly

A vacuum hose connects
the
switch
to the
power
brake booster.
A
wire harness connects
the
switch
to
the brake warning light.
The switch
is
mounted
on the
driver side inner
fender panel just below
the
hood hinge
(Fig. 2),
b

LOW

VACUUM

WARNING
SWITCH
SWITCH

HARNESS

J9105-95

Fig.
2
Diesel
Vacuum
Switch
Location

•

BRAKES
5 - 23
VACUUM PUMP OPERATION

Vacuum pump output is transmitted to the power
brake booster through a supply hose. The hose is con­ nected to an outlet port on the pump housing and to
the check valve in the power brake booster.
Pump output ranges from a minimum of 8.5 to 25
inches vacuum. The pump rotor and vanes are rotated by the pump
drive gear. The drive gear is operated by the cam­
shaft gear. Booster vacuum level is monitored by a warning
switch (Fig. 2). The switch consists of a vacuum
chamber that measures vacuum level and a sensor in
circuit with the brake warning light. The vacuum chamber is connected to the booster
check valve by a vacuum supply hose. A wire har­
ness connects the switch sensor to the brake warning
light. If booster vacuum falls below 8.5 inches for 8-10 seconds or more, the switch sensor completes
the circuit to the warning light causing it to illumi­

nate.

VACUUM PUMP DIAGNOSIS
Vacuum pump diagnosis involves checking pump
output with a vacuum gauge. The low vacuum warn­
ing switch can also be checked with a vacuum gauge.
Refer to the diagnosis procedure in this section. A standard vacuum gauge can be used to check
pump output when necessary. Simply disconnect the
pump supply hose and connect a vacuum gauge to
the outlet port for testing purposes. Vacuum should
hold steady in a range of approximately 8.5 to 25 inches at various engine speeds.
DIAGNOSING LOW VACUUM OUTPUT CONDITION A low booster vacuum condition or a faulty low
vacuum warning switch will cause the brake warn­ ing light to illuminate. If the light does go on and in­
dicates the existence of a low vacuum condition,
check the vacuum pump, booster and warning switch
as follows:
(1) Check vacuum pump oil feed line. Verify that
line connections are secure and not leaking. If leak­ age is noted and pump is noisy, replace pump.
(2) Disconnect supply hose to booster. Connect vac­
uum gauge to this hose and run engine at various
throttle openings. Output should range from 8.5 to 25 inches vacuum. If vacuum is consistently below
8.5 inches, problem is with vacuum hoses or pump
component. If output is within specified limits, con­
tinue testing.
(3) Check booster operation as described in diagno­
sis section. Replace check valve, vacuum hoses, or
booster if necessary. However, if booster operation is correct but warning light is still on, continue testing. (4) Disconnect vacuum hose at warning switch.
Plug hose and connect hand vacuum pump to switch. (5) Start and run engine.
(6) Apply 8.5 to 9 inches of vacuum to warning
switch and observe warning light. If light goes out,
switch vacuum hose is either loose or leaking. If
light remains on, leave engine running and continue
testing.
(7) Apply 20-25 inches vacuum to switch and ob­
serve warning light operation. If light now goes out,
switch is at fault and should be replaced. If light re­
mains on, continue testing.
(8) Reconnect vacuum hoses and replace original
warning switch with known good switch. Run engine and observe warning light operation. If light is now
off, old switch is faulty. If light remains on, problem
is in wiring between switch and warning light.

VACUUM-STEERING PUMP
ASSEMBLY
REMOVAL
(1) Disconnect battery negative cable.
(2) Position drain pan under power steering pump.
(3) Disconnect vacuum and steering pump hoses
from respective pumps (Fig. 3).

Fig.
3
Vacuum
And Steering
Pump Hose
Connections

(4) Disconnect oil pressure sender wires at sender
(Fig. 4).
(5) Remove oil pressure sender (Fig. 4).
(6) Disconnect lubricating oil feed line from fitting
at underside of vacuum pump (Fig. 5).
(7) Remove lower bolt that attaches pump assem­
bly to engine block (Fig. 6).
(8) Remove bottom, inboard nut that attaches
adapter to steering pump (Fig. 6). This nut secures a
small bracket to engine block. Nut and bracket must
be removed before pump assembly can be removed from block.

S
- 24
BRAKES

•

LINE
J9105-96
Fig. 5 Oil Feed Line Connection At Pump (9) Remove upper bolt that attaches pump assem­
bly to engine block (Fig. 7).
(10) Remove pump assembly from vehicle (Fig. 8).

VACUUM PUMP REPLACEMENT
(1) Remove nuts attaching vacuum pump to
adapter (Fig. 8). (2) Remove vacuum pump from adapter (Fig. 9).
Turn pump gear back and forth to disengage pump shaft from coupling if necessary. (3) Inspect adapter O-ring (Fig. 9). Replace O-ring
if cut or torn.
PUMP ASSEMBLY
SOTTOM-INIOAiD
ADAPTER
BRACKET
NUT
J9105-97
Fig. 6 Adapter And
Pump
Mounting Fastener Location Fig. 7 Removing Pump Assembly Upper Mounting
Bolt
(4) Lubricate adapter O-ring with engine oil.
(5) Note position of drive slots in coupling. Then
rotate drive gear to align tangs on vacuum pump shaft with coupling (Fig. 10).
(6) Verify that pump is seated in adapter and cou­
pling.
(7) Install and tighten pump attaching nuts and
washers.

•

BRAKES
5 - 25

ADAPTER
J9105-98

Fig.
8 Pump Assembly Removal

COUPLING

O-RING
PUMP
ADAPTER

J9105-99

Fig.
9
Vacuum
Pump
Removed
From Adapter
ROTATE
DRIVE

GEAR
TO
ALIGN

TANGS
J9105-102

Fig.
10 Aligning Pump Shaft Drive Tangs
PUMP ADAPTER REPLACEMENT

(1) Remove coupling from adapter (Fig. 11).
(2) Remove remaining adapter attaching nuts and
remove adapter from steering pump (Fig. 12). (3) If steering pump will be serviced, remove
spacer from each inboard mounting stud on pump (Fig, 12).
Fig.
11 Removing/Installing
Pump
Drive
Coupling

Fig.
12 Steering
Pump
Mounting
Stud
Spacer
Locations

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