2003 CHRYSLER CARAVAN lock

INSTALLATION
INSTALLATION - FRONT DISC BRAKE CALIPER
(DISC/DISC BRAKES)
CAUTION: TRW and Continental Teves brake cali-
pers are not interchangeable. Each caliper is specif-
ically designed for the unique brake system (TRW -
disc/drum brake combination and Continental Teves
- disc/disc brake combination). If calipers are inter-
changed, improper performance, noise and
increased stopping distance can occur.
(1) Completely retract the caliper piston back into
piston bore of the caliper. Use a C-clamp to retract
the piston if necessary. Place a wood block over the
piston before installing the C-clamp to avoid damag-
ing the piston.
CAUTION: Use care when installing the brake cali-
per assembly onto the steering knuckle, so that the
seals on the caliper guide pin bushings do not get
damaged by the steering knuckle bosses.
(2) Carefully position the brake caliper and shoes
over the brake rotor and adapter.
(3) Install the caliper guide pin bolts and tighten
to a torque of 35 N´m (26 ft. lbs.).Extreme caution
should be taken not to cross thread the caliper
guide pin bolts.
(4) Install the anti-rattle clip on the outboard side
of the caliper. Start the clip into the holes on the cal-
iper, then stretch the clip legs past the abutments on
the caliper adapter.
CAUTION: When connecting the brake hose to the
caliper, install new brake hose to caliper special
copper washers.
(5) Install the brake hose on the caliper. To do
this, first place one NEW special fitting washer on
each side of the hose fitting, then slide the banjo bolt
through the fitting. Next, thread the banjo bolt into
the threaded port on the rear of the brake caliper.
Tighten the banjo bolt to a torque of 47 N´m (35 ft.
lbs.).
(6) Install the wheel and tire assembly. Tighten
the wheel mounting stud nuts in proper sequence
until all nuts are torqued to half specification, then
repeat the tightening sequence to the full specified
torque of 135 N´m (100 ft. lbs.).
(7) Lower the vehicle.
(8) Remove the brake pedal depressor (holding)
tool.
(9) Bleed the hydraulic brake circuit to the brake
caliper. (Refer to 5 - BRAKES - STANDARD PROCE-
DURE)(10) Road test the vehicle and make several stops
to wear off any foreign material on the brakes and to
seat the brake shoe linings.
INSTALLATION - FRONT DISC BRAKE CALIPER
(DISC/DRUM BRAKES)
CAUTION: TRW and Continental Teves brake cali-
pers are not interchangeable. Each caliper is specif-
ically designed for the unique brake system (TRW -
disc/drum brake combination and Continental Teves
- disc/disc brake combination). If calipers are inter-
changed, improper performance, noise and
increased stopping distance can occur.
(1) Completely retract the caliper piston back into
the bore of the caliper. Use a C-clamp to retract the
piston if necessary. Place a wood block over the pis-
ton before installing the C-clamp to avoid damaging
the piston.
CAUTION: Use care when installing the caliper onto
the disc brake adapter to avoid damaging the boots
on the caliper guide pins.
(2) Install the disc brake caliper over the brake
shoes on the brake caliper adapter.
(3) Align the caliper guide pin bolt holes with the
guide pins. Install the caliper guide pin bolts and
tighten them to a torque of 35 N´m (26 ft. lbs.) (Fig.
32).
(4) Install the banjo bolt connecting the brake hose
to the brake caliper (Fig. 32). Install NEW copper
washers on each side of the hose fitting as the banjo
bolt is guided through the fitting. Thread the banjo
bolt into the caliper and tighten it to a torque of 47
N´m (35 ft. lbs.).
(5) Install the tire and wheel assembly. Tighten
the wheel mounting nuts to a torque of 135 N´m (100
ft. lbs.).
(6) Lower the vehicle.
(7) Remove the brake pedal holding tool.
(8) Bleed the caliper as necessary. (Refer to 5 -
BRAKES - BASE - STANDARD PROCEDURE).
(9) Road test the vehicle and make several stops to
wear off any foreign material on the brakes and to
seat the brake shoes.
DISC BRAKE CALIPER - REAR
REMOVAL - REAR DISC BRAKE CALIPER
NOTE: Handling of the rotor and caliper, must be
done in such a way as to avoid damage to the rotor
and scratching or nicking of lining on the brake
shoes.
RSBRAKES - BASE5-27
DISC BRAKE CALIPER - FRONT (Continued)
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(3) Install the disc brake caliper over the brake
shoes on the brake caliper adapter.
(4) Align the caliper guide pin bolt holes with the
guide pins. Install the caliper guide pin bolts and
tighten them to a torque of 35 N´m (26 ft. lbs.) (Fig.
43).
(5) Install the tire and wheel assembly. Tighten
the wheel mounting nuts to a torque of 135 N´m (100
ft. lbs.).
(6) Lower the vehicle.
(7) Pump the brake pedal several times before
moving the vehicle to set the shoes to the brake
rotor.
DRUM
REMOVAL
(1) Raise the vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(2) Remove the tire and wheel assembly from the
vehicle
(3) Remove the rear brake shoe adjusting hole
cover plug.
(4) Insert a thin screwdriver into brake adjusting
hole and hold adjusting lever away from notches of
adjusting screw star wheel.
(5) Insert another thin screwdriver into brake
adjusting hole and engage notches of brake adjusting
screw star wheel. Release brake adjustment by pry-
ing down with adjusting tool.
(6) Remove rear brake drum from rear hub/bear-
ing assembly.NOTE: It may be necessary to insert M8 X 1.25 MM
bolts into the two removal holes on the drum to
force the drum off the hub.
INSTALLATION
(1) Adjust brake shoe assemblies so as not to inter-
fere with brake drum installation.
(2) Install the rear brake drums on the hubs.
(3) Adjust drum brake shoes as necessary per pro-
cedure found in the Adjustment section of this ser-
vice manual group (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/DRUM -
ADJUSTMENTS).
(4) Install wheel and tire assembly.
(5) Tighten the wheel mounting stud nuts in
proper sequence until all nuts are torqued to half
specification. Then repeat the tightening sequence to
the full specified torque of 135 N´m (100 ft. lbs.).
(6) Lower the vehicle.
FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder, propor-
tioning valve, caliper seals, wheel cylinder seals,
Antilock Brake hydraulic unit and all hydraulic fluid
hoses.
STANDARD PROCEDURE - BRAKE FLUID
LEVEL CHECKING
Check master cylinder reservoir fluid level a mini-
mum of twice annually.
Fluid reservoirs are marked with the words FULL
and ADD to indicate proper brake fluid fill level of
the master cylinder.
If necessary, add brake fluid to bring the level to
the bottom of the FULL mark on the side of the mas-
ter cylinder fluid reservoir.
Use only Mopartbrake fluid or equivalent from a
sealed container. Brake fluid must conform to DOT 3
specifications (DOT 4 or DOT 4+ are acceptable).
DO NOTuse brake fluid with a lower boiling
point, as brake failure could result during prolonged
hard braking.
Fig. 44 Guide Pins And Boots
1 - PINS
2 - BOOTS
5 - 32 BRAKES - BASERS
DISC BRAKE CALIPER GUIDE PINS (Continued)
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Use only brake fluid that was stored in a tightly-
sealed container.
DO NOTuse petroleum-based fluid because seal
damage will result. Petroleum based fluids would be
items such as engine oil, transmission fluid, power
steering fluid etc.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications (DOT 4 and DOT 4+ are
acceptable) and SAE J1703 standards. No other type
of brake fluid is recommended or approved for usage
in the vehicle brake system. Use only MopartBrake
Fluid or equivalent from a tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
JUNCTION BLOCK
DESCRIPTION - NON-ABS JUNCTION BLOCK
A junction block is used on vehicles that are not
equipped with antilock brakes (ABS). The junction
block mounts in the same location as the integrated
control unit (ICU) does on vehicles equipped with
ABS. This allows for use of the same brake tube con-
figuration on all vehicles. The junction block is
located on the driver's side of the front suspension
cradle/crossmember below the master cylinder (Fig.
45).
It has six threaded ports to which the brake tubes
connect. Two are for the primary and secondary
brake tubes coming from the master cylinder. The
remaining four are for the chassis brake tubes going
to each brake assembly.
OPERATION - NON-ABS JUNCTION BLOCK
The junction block distributes the brake fluid com-
ing from the master cylinder primary and secondary
ports to the four chassis brake tubes leading to the
brakes at each wheel. Since the junction blockmounts in the same location as the ABS integrated
control unit (ICU), it allows for the common use of
brake tubes going to the brakes whether the vehicle
is equipped with or without ABS.
NOTE: Although the brake tubes coming from the
master cylinder to the junction block or ABS ICU
may appear to be the same, they are not. They are
unique to each brake system application.
REMOVAL - NON-ABS JUNCTION BLOCK
(1) Using a brake pedal depressor, move and lock
the brake pedal to a position past its first 1 inch of
travel. This will prevent brake fluid from draining
out of the master cylinder when the brake tubes are
removed from the junction block.
(2) Disconnect the battery negative cable.
(3) If the vehicle is equipped with speed control,
perform the following:
(a) Disconnect the battery positive cable.
(b) Remove the battery (Refer to 8 - ELECTRI-
CAL/BATTERY SYSTEM/BATTERY - REMOVAL).
(c) Disconnect the vacuum hose connector at the
tank built into the battery tray.
(d) Remove the screw securing the coolant filler
neck to the battery tray.
(e) Remove the battery tray (Refer to 8 - ELEC-
TRICAL/BATTERY SYSTEM/TRAY - REMOVAL).
(f) Remove the fasteners and move the speed
control servo off to the side, out of the way.
CAUTION: Before removing the brake tubes from
the junction block, the junction block and the brake
tubes must be thoroughly cleaned. This is required
to prevent contamination from entering the brake
hydraulic system.
(4) Remove the four chassis brake tubes from the
top of the junction block (Fig. 45).
(5) Remove the primary and secondary brake
tubes from the top of the junction block.
(6) Remove the bolts attaching the junction block
mounting bracket to the front suspension crossmem-
ber (Fig. 45), then remove the junction block.
INSTALLATION - NON-ABS JUNCTION BLOCK
(1) Install the junction block and mounting bracket
on the front suspension crossmember (Fig. 45).
Install the mounting bolts and tighten to a torque of
28 N´m (250 in. lbs.).
(2) Install the primary and secondary brake tubes
from the master cylinder in their ports. Tighten tube
nuts to a torque of 17 N´m (145 in. lbs.).Take care
not to twist tubes when tightening tube nuts.
They must be properly positioned to allow free
RSBRAKES - BASE5-33
FLUID (Continued)
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movement with rubber isolated suspension
crossmember.
(3) Install the four chassis brake tubes into the
outlet ports of the junction block. Tighten all 6 tube
nuts to a torque of 17 N´m (145 in. lbs.).
(4) If the vehicle is equipped with speed control,
perform the following:
(a) Install the speed control servo with its
mounting nuts.
(b) Connect the wiring harness to the speed con-
trol servo.
(c) Install the battery tray (Refer to 8 - ELEC-
TRICAL/BATTERY SYSTEM/TRAY - INSTALLA-
TION).
(d) Install the screw securing the coolant filler
neck to the battery tray.
(e) Reconnect the vacuum hose connector at the
tank built into the battery tray.
(f) Install the battery (Refer to 8 - ELECTRI-
CAL/BATTERY SYSTEM/BATTERY - INSTALLA-
TION).
(g) Install the battery shield.
(5) Remove the brake pedal holder.
(6) Connect negative cable back on negative post of
the battery.
(7) Bleed the brake system thoroughly to ensure
that all air has been expelled from the hydraulic sys-
tem. (Refer to 5 - BRAKES - STANDARD PROCE-
DURE).
(8) Road test the vehicle to verify proper operation
of the brake system.
MASTER CYLINDER
DESCRIPTION
DESCRIPTION
The master cylinder is located on the power brake
booster in the engine compartment on the driver's
side (Fig. 46). This vehicle uses 3 different master
cylinders. Master cylinder usage depends on what
type of brake system the vehicle is equipped with.
CAUTION: Master cylinders are not interchangeable
between systems. Performance and stopping dis-
tance issues will result if the incorrect master cyl-
inder is installed on the vehicle.
For information on master cylinder application,
bore and type, view the following table:
BRAKE SYSTEMMASTER CYLINDER
BORE/TYPE
Disc/Drum - ABS23.8 mm (15/16 in.)
Conventional
Compensating Port
Disc/Drum - Non-ABS23.8 mm (15/16 in.)
Conventional
Compensating Port
Disc/Disc - ABS25.4 mm (1.0 in.)
Conventional
Compensating Port
Disc/Disc ABS With
Traction Control25.4 mm (1.0 in.) Dual
Center Port
Fig. 45 NON-ABS JUNCTION BLOCK
1 - MASTER CYLINDER
2 - JUNCTION BLOCK
3 - SUSPENSION CROSSMEMBER
4 - MOUNTING BOLTS
Fig. 46 Master Cylinder And Booster Location
1 - MASTER CYLINDER
2 - POWER BRAKE BOOSTER
5 - 34 BRAKES - BASERS
JUNCTION BLOCK (Continued)
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CAUTION: Before removing the master cylinder
from the power brake vacuum booster, the master
cylinder and vacuum booster must be thoroughly
cleaned. This must be done to prevent dirt particles
from falling into the power brake vacuum booster.
(12) Clean area where master cylinder assembly
attaches to power brake booster. Use only a solvent
such as MopartBrake Parts Cleaner or equivalent.
(13) Disconnect primary and secondary brake
tubes from ABS integrated control unit or non-ABS
junction block (Fig. 59). Install sealing plugs in the
now open brake tube ports and install caps on ends
of tubes.
NOTE: It is not necessary to remove the brake
tubes from the master cylinder when removing the
master cylinder from the vacuum booster.
(14) Remove two nuts attaching master cylinder to
power brake booster (Fig. 59).
(15) Slide master cylinder straight out of power
brake booster. Remove master cylinder with primary
and secondary tubes from vehicle.
CAUTION: A seal on the rear of the master cylinder
is used to create the seal for holding vacuum in the
power brake vacuum booster. The vacuum seal on
the master cylinder MUST be replaced whenever the
master cylinder is removed from the power brake
vacuum booster.
(16) Disconnect vacuum hose from check valve
located on vacuum booster.DO NOT REMOVE
CHECK VALVE FROM POWER BRAKE
BOOSTER.(17) Inside vehicle, remove silencer panel under
instrument panel below steering column.
(18) Locate the booster input rod to brake pedal
connection under the instrument panel. Position a
small screwdriver between the center tang on the
power brake booster input rod to brake pedal pin
retaining clip (Fig. 60).
(19) Rotate screwdriver enough to allow retaining
clip center tang to pass over end of brake pedal pin.
Then pull retaining clip off brake pedal pin.Discard
retaining clip. It is not to be reused. Replace
only with a new retaining clip when assem-
bling.
(20) Slide booster input rod off pedal pin.
(21) Remove the four nuts attaching power brake
booster to dash panel (Fig. 61).
(22) Slide power brake booster forward and remove
through engine compartment (Fig. 62).
CAUTION: Do not attempt to disassemble the power
brake vacuum booster. It is serviced ONLY as a
complete assembly.
REMOVAL - RHD
CAUTION: Reserve vacuum in power brake booster
must be pumped down (removed) before removing
master cylinder from booster. This is necessary to
prevent booster from sucking in any contamination
as master cylinder is removed. This can be done
simply by pumping the brake pedal, with the vehi-
cle's engine not running, until a firm feeling brake
pedal is achieved.
Fig. 59 Master Cylinder Mounting
1 - MASTER CYLINDER MOUNTING NUTS
2 - MASTER CYLINDER
3 - SECONDARY TUBE NUT AT ICU
4 - PRIMARY TUBE NUT AT ICU
Fig. 60 Vacuum Booster Input Rod Retaining Pin
1 - BRAKE PEDAL
2 - INPUT ROD
3 - SCREWDRIVER
4 - RETAINING CLIP
5 - BRAKE PEDAL PIN
RSBRAKES - BASE5-43
POWER BRAKE BOOSTER (Continued)
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INSTALLATION
INSTALLATION - LHD
(1) Position power brake booster on dash panel
using the reverse procedure of its removal (Fig. 62).
It may be necessary to push in on booster input rod
as it is guided through the dash panel.
(2) Install the four nuts mounting the booster to
the dash panel (Fig. 61). Tighten the mounting nuts
to a torque of 29 N´m (250 in. lbs.).
(3) Using lubriplate, or equivalent, coat the sur-
face of the brake pedal pin where it contacts the
booster input rod.
CAUTION: When installing the brake pedal pin on
the power brake booster input rod, do not re-use
the old retaining clip.
(4) Install booster input rod on brake pedal pin
and install a NEW retaining clip (Fig. 68).
CAUTION: Do not reuse the original brake lamp
switch. The switch can only be adjusted once. That
is during initial installation of the switch. If the
switch is not adjusted properly or has been
removed for some service, a new switch must be
installed and adjusted.
(5) Remove and replace the brake lamp switch
with a NEW switch. (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/BRAKE LAMP
SWITCH - REMOVAL), (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/BRAKE LAMP
SWITCH - INSTALLATION)
(6) Install the silencer panel below the steering
column.(7) Connect vacuum hose to check valve on power
brake booster.
CAUTION: The master cylinder (and its rear seal) is
used to create the seal for holding vacuum in the
vacuum booster. The vacuum seal on the master
cylinder MUST be replaced with a NEW seal when-
ever the master cylinder is removed from the vac-
uum booster.
CAUTION: When removing the vacuum seal from
the master cylinder do not use a sharp tool.
(8) Using a soft tool such as a trim stick, remove
the vacuum seal from the master cylinder mounting
flange.
(9) Install a NEW vacuum seal on rear mounting
flange of the master cylinder (Fig. 69).
(10) Position master cylinder on studs of booster,
aligning push rod on booster with master cylinder
piston.
(11) Install the two nuts mounting the master cyl-
inder to the booster (Fig. 59). Tighten both mounting
nuts to a torque of 25 N´m (225 in. lbs.).
(12) Connect wiring harness connector to brake
fluid level switch in the master cylinder fluid reser-
voir (Fig. 58).
(13) Connect primary and secondary brake tubes
to ABS ICU or non-ABS junction block (Fig. 59).
Tighten the tube nuts to 17 N´m (145 in lbs.).
(14) Install wiper module (unit). (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/WIPER MOD-
ULE - INSTALLATION)
(15) If equipped with speed control, install speed
control servo and connect wiring connector. Tighten
Fig. 67 RHD Booster Removal/Installation
1 - POWER BRAKE BOOSTER
2 - MASTER CYLINDER
Fig. 68 Retaining Pin Installed On Brake Pedal Pin
1 - BRAKE PEDAL
2 - RETAINING CLIP
3 - BOOSTER INPUT ROD
5 - 46 BRAKES - BASERS
POWER BRAKE BOOSTER (Continued)
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(12) If the vehicle is equipped with the 2.5L diesel
engine, install the coolant recovery pressure con-
tainer and bracket. (Refer to 7 - COOLING/ENGINE/
COOLANT RECOVERY PRESS CONTAINER -
INSTALLATION)
(13) If equipped with speed control, install speed
control servo and connect wiring connector. Tighten
the mounting nuts to a torque of 14 N´m (124 in.
lbs.).
(14) Install the battery tray. Install the two nuts
and one bolt attaching the battery tray to the vehicle.
Tighten the bolt and nuts to a torque of 14 N´m (124
in. lbs.).
(15) If vehicle is equipped with speed control, con-
nect the servo vacuum hose to the vacuum tank on
the battery tray.
(16) Install the battery, clamp and mounting nut.
(17) Install the positive battery cable on the bat-
tery.
(18) Install the negative battery cable on the bat-
tery.
(19) Install the battery thermal guard shield.
CAUTION: Do not reuse the original brake lamp
switch. The switch can only be adjusted once. That
is during initial installation of the switch. If the
switch is not adjusted properly or has been
removed for some service, a new switch must be
installed and adjusted.
(20) Remove and replace the brake lamp switch
with a NEW switch. (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/BRAKE LAMP
SWITCH - REMOVAL), (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/BRAKE LAMP
SWITCH - INSTALLATION)(21) Bleed the base brakes as necessary. (Refer to
5 - BRAKES - STANDARD PROCEDURE)
(22) Road test vehicle to ensure proper operation
of the brakes.
PROPORTIONING VALVE
DESCRIPTION - PROPORTIONING VALVE
(HEIGHT SENSING)
NOTE: Only vehicles without antilock brakes (ABS)
have a proportioning valve. Vehicles with ABS uti-
lize electronic brake distribution which is controlled
through the ABS integrated control unit.
Vehicles not equipped with ABS use a height sens-
ing proportioning valve. It is mounted to the body of
the vehicle above the rear axle (Fig. 72). It has an
actuator lever that attaches to the rear axle and
moves with the axle to help the valve sense the vehi-
cle height.
CAUTION: The height sensing proportioning valve
is not adjustable. No attempt should be made to
adjust it. It is replaced as a complete assembly.
CAUTION: The use of after-market load leveling or
load capacity increasing devices on this vehicle are
prohibited. Using air shock absorbers or helper
springs on this vehicle will cause the height sens-
ing proportioning valve to inappropriately reduce
the hydraulic pressure to the rear brakes. This inap-
propriate reduction in hydraulic pressure potentially
could result in increased stopping distance of the
vehicle.
OPERATION - PROPORTIONING VALVE
(HEIGHT SENSING)
Vehicles not equipped with ABS use a height sens-
ing proportioning valve.
The height sensing proportioning valve operates
similarly to a standard proportioning valve in the fol-
lowing way. As hydraulic pressure is applied to the
valve, full input hydraulic pressure is supplied to the
rear brakes up to a certain pressure point, called the
split point. Beyond the split point, the proportioning
valve reduces the amount of hydraulic pressure to
the rear brakes according to a given ratio. Thus, on
light brake applications, approximately equal
hydraulic pressure will be transmitted to both the
front and rear brakes. Upon heavier brake applica-
tions, the hydraulic pressure transmitted to the rear
brakes will be lower than the front brakes. This will
prevent premature rear wheel lockup and skid.
Fig. 71 Vacuum Seal (Typical)
1 - MASTER CYLINDER ASSEMBLY
2 - VACUUM SEAL
5 - 48 BRAKES - BASERS
POWER BRAKE BOOSTER (Continued)
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Here is how the height sensing proportioning valve
differs from a standard proportioning valve. As the
height of the rear suspension changes, the height
sensing portion of the proportioning valve changes
the split point of the proportioning valve. When the
height of the rear suspension is low, the proportion-
ing valve interprets this as extra load and the split
point of the proportioning valve is raised to a higher
pressure to allow for more rear braking. When the
height of the rear suspension is high, the proportion-
ing valve interprets this as a light load and the split
point of the proportioning valve is lowered to a lower
pressure and rear braking is reduced.
The height sensing proportioning valve regulates
the pressure by sensing the load condition of the
vehicle through the movement of the proportioning
valve actuator lever (Fig. 72). As the position of the
rear axle changes, depending on the load the vehicle
is carrying, the movement is transferred to the pro-
portioning valve. The proportioning valve adjusts the
hydraulic pressure accordingly.
The height sensing proportioning valve allows the
brake system to maintain the optimal front to rear
brake balance regardless of the vehicle load condi-
tion. Under a light load condition, hydraulic pressure
to the rear brakes is minimized. As the rear load con-
dition increases, so does the hydraulic pressure to
the rear brakes.
DIAGNOSIS AND TESTING - PROPORTIONING
VALVE (HEIGHT SENSING)
CAUTION: The use of aftermarket load leveling or
load capacity increasing devices on this vehicle is
prohibited. Using air shock absorbers or helpersprings on this vehicle will cause the height sens-
ing proportioning valve to inappropriately reduce
the hydraulic pressure to the rear brakes. This inap-
propriate reduction in hydraulic pressure potentially
could result in increased stopping distance of the
vehicle.
When a premature rear wheel skid is obtained on a
brake application, it may be an indication that the
hydraulic pressure to the rear brakes is above the
specified output from the proportioning valve. This
condition indicates a possible malfunction of the
height sensing proportioning valve, which will
require testing to verify that it is properly controlling
the hydraulic pressure allowed to the rear brakes.
Premature rear wheel skid may also be caused by
contaminated front or rear brake linings.
Prior to testing a proportioning valve for function,
check that all tire pressures are correct. Also, ensure
the front and rear brake linings are in satisfactory
condition.It is also necessary to verify that the
brakes shoe assemblies on a vehicle being
tested are either original equipment manufac-
turers (OEM) or original replacement brake
shoe assemblies meeting the OEM lining mate-
rial specification. This vehicles brake system is
not balanced for aftermarket brake shoe assem-
bly lining material.
If both front and rear brakes check OK, proceed
with the following test procedure for the height sens-
ing proportioning valve.
(1) Road test the vehicle to determine which rear
wheel brake is exhibiting premature wheel skid.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE)
(3) Remove the chassis brake tube going to the
rear brake in question at the proportioning valve.
Remove the chassis brake tube coming from the junc-
tion block at the proportioning valve (Fig. 73).
(4) Install the appropriate fittings from Pressure
Test Fittings, Special Tool 6833, into the open ports
of the proportioning valve.
(5) Install the previously removed brake lines into
the Pressure Test Fittings. Tighten all tube nuts to
17 N´m (145 in. lbs.).
(6) Install a pressure gauge from Gauge Set, Spe-
cial Tool C-4007-A into the open port on each pres-
sure test fitting. Bleed air out of hose from pressure
test fittings to pressure gauges at the pressure
gauges. Then bleed air out of the brake line being
tested at that rear wheel brake bleeder.
NOTE: Actuator rod is a linear spring and is meant
to flex by design. When rod is raised, it will have
some curvature to it.
Fig. 72 HEIGHT SENSING PROPORTIONING VALVE
1 - PROPORTIONING VALVE
2 - ACTUATOR LEVER
3 - AXLE BRACKET
4 - REAR AXLE
RSBRAKES - BASE5-49
PROPORTIONING VALVE (Continued)
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