brake light DODGE TOWN AND COUNTRY 2001 User Guide

(6) The half shaft is spring loaded. Compress inner
half shaft joint slightly and pull downward to clear
rear differential output flange. Then pull half shaft
assembly outward to remove (Fig. 3).
INSTALLATION
(1) Install the outer CV joint stub shaft through
the hub bearing (Fig. 4).
(2) The half shaft is spring loaded. Compress inner
half shaft joint slightly and push upward until the
inner CV joint flange engages the rear differential
output flange.(3) Install the inner half shaft retaining bolts (Fig.
5). Torque the bolts to 61 N´m (45 ft.lbs.).
(4) Install the half shaft washer and hub nut.
Torque the hub nut to 244 N´m (180 ft.lbs.).
(5) Install the wave washer, nut lock, and a new
cotter pin (Fig. 6). Be sure to wrap the cotter pin
prongs tightly around the hub nut lock.
(6) Install rear wheel. Torque the lug nuts to 135
N´m (100 ft.lbs.).
Fig. 1 Cotter Pin, Nut Lock, And Wave Washer
1 - HUB NUT
2 - NUT LOCK
3 - COTTER PIN
4 - WAVE WASHER
Fig. 2 Inner Half Shaft Bolts
1 - SHAFT
2 - FLANGE
Fig. 3 Half Shaft Removal
1 - BRAKE BACKING PLATE
2 - HALF SHAFT
Fig. 4 Half Shaft Installation
1 - BRAKE BACKING PLATE
2 - HALF SHAFT
RSHALF SHAFT - REAR3-17
HALF SHAFT - REAR (Continued)
ProCarManuals.com

JUNCTION BLOCK
DESCRIPTION...........................32
OPERATION.............................32
REMOVAL..............................32
INSTALLATION...........................33
MASTER CYLINDER
DESCRIPTION...........................33
OPERATION.............................34
STANDARD PROCEDURE..................34
MASTER CYLINDER BLEEDING...........34
REMOVAL..............................34
DISASSEMBLY...........................35
ASSEMBLY.............................36
INSTALLATION...........................36
POWER BRAKE BOOSTER
DESCRIPTION...........................37
OPERATION.............................37
DIAGNOSIS AND TESTING.................38
POWER BRAKE BOOSTER...............38
REMOVAL..............................38
INSTALLATION...........................40
PROPORTIONING VALVE
DESCRIPTION...........................41
OPERATION.............................42
DIAGNOSIS AND TESTING.................42
PROPORTIONING VALVE (HEIGHT
SENSING).............................42
REMOVAL..............................43
INSTALLATION...........................43
ROTORS
DIAGNOSIS AND TESTING.................44BRAKE ROTOR........................44
STANDARD PROCEDURE..................47
BRAKE ROTOR MACHINING..............47
REMOVAL..............................48
INSTALLATION...........................48
SUPPORT PLATE - DRUM BRAKE
REMOVAL..............................48
INSTALLATION...........................49
WHEEL CYLINDERS
REMOVAL..............................50
INSPECTION............................50
INSTALLATION...........................50
PARKING BRAKE
DESCRIPTION...........................50
OPERATION.............................51
STANDARD PROCEDURE..................51
PARKING BRAKE AUTOMATIC ADJUSTER
MECHANISM RELEASE..................51
PARKING BRAKE AUTOMATIC ADJUSTER
RESET...............................51
LEVER - PARKING BRAKE
REMOVAL..............................52
INSTALLATION...........................53
SHOES - PARKING BRAKE
REMOVAL..............................53
INSTALLATION...........................58
ADJUSTMENTS..........................59
CABLES - PARKING BRAKE
REMOVAL..............................61
INSTALLATION...........................65
ADJUSTMENTS..........................66
BRAKES - BASE
DESCRIPTION - BASE BRAKES
The base brake system consists of the following
components:
²Brake pedal
²Power brake booster
²Master cylinder
²Brake tubes and hoses
²Proportioning valve (non-ABS vehicles only)
²Disc brakes
²Drum brakes
²Brake lamp switch
²Brake fluid level switch
²Parking brakes
Front disc brakes control the braking of the front
wheels; rear braking is controlled by rear drum
brakes or rear disc brakes depending on options.
The hydraulic brake system is diagonally split on
both the non-antilock braking systems and antilock
braking systems. That means the left front and right
rear brakes are on one hydraulic circuit and the right
front and left rear are on the other.For information on the brake lamp switch, (Refer
to 8 - ELECTRICAL/LAMPS/LIGHTING - EXTERI-
OR/BRAKE LAMP SWITCH - DESCRIPTION)
Vehicles equipped with the optional antilock brake
system (ABS) use a system designated Mark 20e. It
is available with or without traction control. This
system shares most base brake hardware used on
vehicles without ABS. ABS components are described
in detail in ANTILOCK BRAKE SYSTEM.
OPERATION - BASE BRAKES
When a vehicle needs to be stopped, the driver
applies the brake pedal. The brake pedal pushes the
input rod of the power brake booster into the booster.
The booster uses vacuum to ease pedal effort as force
is transferred through the booster to the master cyl-
inder. The booster's output rod pushes in the master
cylinder's primary and secondary pistons applying
hydraulic pressure through the chassis brake tubes
to the brakes at each tire and wheel assembly.
The parking brakes are foot-operated. When
applied, the parking brake lever pulls on cables that
actuate brake shoes at each rear wheel. These shoes
come in contact with a hub mounted drum (drum for
5 - 2 BRAKES - BASERS
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RED BRAKE WARNING INDICATOR LAMP
CONDITION POSSIBLE CAUSES CORRECTION
RED BRAKE WARNING
LAMP ON1. Parking brake lever not fully
released.1. Release parking brake lever.
2. Parking brake warning lamp
switch on parking brake lever.2. Inspect and replace switch as necessary.
3. Brake fluid level low in reservoir. 3. Fill reservoir. Check entire system for
leaks. Repair or replace as required.
4. Brake fluid level switch. 4. Disconnect switch wiring connector. If
lamp goes out, replace switch.
5. Mechanical instrument cluster
(MIC) problem.5. Refer to appropriate Diagnostic
information.
6. Amber ABS Warning Indicator
Lamp also illuminated.6. Refer to appropriate Diagnostic
information.
BRAKE NOISE
CONDITION POSSIBLE CAUSES CORRECTION
CLICK OR SQUAWK ON
PEDAL APPLICATION1. Brake lamp switch. 1. Replace switch.
2. Brake Transmission Shift Interlock
Linkage.2. Lubricate BTSI linkage.
3. Pedal pivot bushings 3. Lubricate pivot bushings. Replace if
necessary.
DISC BRAKE CHIRP 1. Excessive brake rotor runout. 1. Follow brake rotor diagnosis and testing.
Correct as necessary.
2. Lack of lubricant on brake caliper
slides.2. Lubricate brake caliper slides.
3. Caliper/shoes not fully seated. 3. Reseat caliper/shoes.
DISC BRAKE RATTLE OR
CLUNK1. Broken or missing anti-rattle
spring clips on shoes.1. Replace brake shoes.
2. Caliper guide pins/bolts loose. 2. Tighten guide pins/bolts.
DISC BRAKE SQUEAK AT
LOW SPEED (WHILE
APPLYING LIGHT BRAKE
PEDAL EFFORT)1. Brake shoe linings. 1. Replace brake shoes.
DRUM BRAKE CHIRP 1. Lack of lubricant on brake shoe
support plate where shoes ride.1. Lubricate shoe contact areas on brake
shoe support plates.
DRUM BRAKE CLUNK 1. Drum(s) have threaded machined
braking surface.1. Reface or replace drake drums as
necessary.
DRUM BRAKE HOWL OR
MOAN1. Lack of lubricant on brake shoe
support plate where shoes ride and
at the anchor.1. Lubricate shoe contact areas on brake
shoe support plates and at the anchor.
2. Rear brake shoes. 2. Replace rear brake shoes.
DRUM BRAKE SCRAPING
OR WHIRRING1. ABS wheel speed sensor or tone
wheel.1. Inspect, correct or replace faulty
component(s).
5 - 4 BRAKES - BASERS
BRAKES - BASE (Continued)
ProCarManuals.com

(20) Road test vehicle. The automatic adjuster will
continue the brake adjustment during the road test
of the vehicle.
ADJUSTMENT - REAR DRUM BRAKE SHOES
NOTE: Normally, self-adjusting drum brakes do not
require manual brake shoe adjustment. Although, in
the event of a brake shoe replacement, it is advis-
able to make the initial adjustment manually to
speed up the adjusting time.
NOTE: Before raising the vehicle, verify the parking
brake lever is fully released.
(1) Raise the vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(2) Remove rubber plug from rear brake adjusting
hole in the rear brake support plate.
(3) Insert a thin screwdriver through the adjusting
hole in the support plate and against the star wheel
of the adjusting screw. Move handle of the tool
upward rotating the star wheel until a slight drag is
felt when tire and wheel assembly is rotated.
(4) Insert a second thin screwdriver or piece of
welding rod into brake adjusting hole and push the
adjusting lever out of engagement with the star
wheel.Care should be taken so as not to bend
adjusting lever or distort lever spring.
(5) While holding the adjusting lever out of
engagement, back off the star wheel just enough to
ensure a free wheel with no brake shoe drag.
(6) Repeat the above adjustment at the other rear
wheel.
(7) Install the adjusting hole rubber plugs back in
the rear brake support plates.
(8) Lower the vehicle.
DISC BRAKE CALIPERS -
FRONT
REMOVAL - FRONT DISC BRAKE CALIPER
(DISC/DISC BRAKES)
(1) Depress the brake pedal past its first inch of
travel and hold it in this position using a brake pedal
depressor (holding) tool. This is done to isolate the
master cylinder from the brake hydraulic system dis-
allowing the brake fluid to completely drain out of
the brake fluid reservoir.
(2) Raise the vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(3) Remove front wheel and tire assembly.(4) Remove the banjo bolt connecting the brake
hose to the brake caliper. There are two washers (one
on each side of the brake hose fitting) that will come
off with the banjo bolt. Discard these washers.
(5) Remove the 2 caliper guide pin bolts.
(6) Remove the brake caliper from the adapter.
REMOVAL - FRONT DISC BRAKE CALIPER
(DISC/DRUM BRAKES)
(1) Using a brake pedal holding tool, depress the
brake pedal past its first one inch of travel and hold
it in this position. This will isolate the master cylin-
der from the brake hydraulic system and will not
allow the brake fluid to drain out of the master cyl-
inder reservoir when the lines are opened.
(2) Raise the vehicle. Refer to HOISTING in
LUBRICATION AND MAINTENANCE.
(3) Remove the front tire and wheel assembly.
(4) Remove the banjo bolt connecting the brake
hose to the brake caliper (Fig. 32). There are two
washers (one on each side of the flex hose fitting)
that will come off with the banjo bolt. Discard the
washers.
(5) Remove the two brake caliper guide pin bolts
(Fig. 32).
(6) Remove the disc brake caliper from the disc
brake adapter.
Fig. 32 Brake Caliper Mounting (Typical)
1 - BRAKE HOSE
2 - ADAPTER MOUNTING BOLTS
3 - BANJO BOLT
4 - CALIPER GUIDE PIN BOLTS
5 - 22 BRAKES - BASERS
BRAKE PADS/SHOES - REAR DRUM (Continued)
ProCarManuals.com

DISASSEMBLY - CALIPER GUIDE PIN
BUSHINGS (DISC/DISC BRAKES)
Before disassembling the brake caliper, clean and
inspect it. Refer to CLEANING or INSPECTION in
this section.
(1) Using your fingers, collapse one side of the rub-
ber guide pin bushing. Pull the guide pin bushing out
the other side of the brake caliper mounting boss.
(2) Repeat this procedure on the remaining bush-
ing.
DISASSEMBLY - CALIPER PISTON AND SEAL
WARNING: UNDER NO CONDITION SHOULD HIGH
PRESSURE AIR EVER BE USED TO REMOVE A PIS-
TON FROM A CALIPER BORE. PERSONAL INJURY
COULD RESULT FROM SUCH A PRACTICE.
NOTE: Before disassembling the brake caliper,
clean and inspect it. Refer to CLEANING AND
INSPECTION in this section.
NOTE: The safest way to remove the piston from
the caliper bore is to use the hydraulic pressure of
the vehicle's brake system.
(1) Following the removal procedure in DISC
BRAKE SHOES found in this section, remove the
caliper from the brake rotor and hang the assembly
on a wire hook away from rotor and body of the vehi-
cle so brake fluid cannot get on these components.
Remove the brake shoes, and place a small piece of
wood between the piston and caliper fingers.
(2) Carefully depress the brake pedal to hydrauli-
cally push piston out of its bore. Once completed,
apply and hold down the brake pedal to any position
beyond the first inch of pedal travel using a brake
pedal holding tool. This will prevent the fluid in the
master cylinder reservoir from completely draining
out.
(3) Disconnect the brake fluid flex hose from the
caliper assembly and remove it from the vehicle.
CAUTION: Do not use excessive force when clamp-
ing caliper in vise. Excessive vise pressure will
cause bore distortion.(4) Mount the caliper in a vise equipped with pro-
tective jaws.
(5) Remove the piston dust boot from the caliper
and discard.
NOTE: Do not use a screw driver or other metal tool
for seal removal. Using such tools can scratch the
bore or leave burrs on the seal groove edges.
(6) Using a soft tool such as a plastic trim stick,
work the piston seal out of its groove in caliper pis-
ton bore (Fig. 33). Discard the old seal.
(7) Clean the piston bore and drilled passage ways
using alcohol or a suitable solvent. Wipe it dry using
only a lint-free cloth.
(8) Inspect the piston bore for scoring or pitting.
Bores that show light scratches or corrosion can usu-
ally be cleared of the light scratches or corrosion
using crocus cloth.
Fig. 33 Removing Piston Seal
1 - PLASTIC TRIM STICK
2 - CALIPER
3 - PISTON SEAL GROOVE
4 - PISTON SEAL
RSBRAKES - BASE5-23
DISC BRAKE CALIPERS - FRONT (Continued)
ProCarManuals.com

DISASSEMBLY - CALIPER PISTON AND SEAL
WARNING: UNDER NO CONDITION SHOULD HIGH
PRESSURE AIR EVER BE USED TO REMOVE A PIS-
TON FROM A CALIPER BORE. PERSONAL INJURY
COULD RESULT FROM SUCH A PRACTICE.
NOTE: Before disassembling the brake caliper,
clean and inspect it. Refer to CLEANING AND
INSPECTION in this section.
NOTE: The safest way to remove the piston from
the caliper bore is to use the hydraulic pressure of
the vehicle's brake system.
(1) Following the removal procedure in DISC
BRAKE SHOES found in this section, remove the
caliper from the brake rotor and hang the assembly
on a wire hook away from rotor and body of the vehi-
cle so brake fluid cannot get on these components.
Remove the brake shoes, and place a small piece of
wood between the piston and caliper fingers.
(2) Carefully depress the brake pedal to hydrauli-
cally push piston out of its bore. Once completed,
apply and hold down the brake pedal to any position
beyond the first inch of pedal travel using a brake
pedal holding tool. This will prevent the fluid in the
master cylinder reservoir from completely draining
out.(3) Disconnect the brake fluid flex hose from the
caliper assembly and remove it from the vehicle.
CAUTION: Do not use excessive force when clamp-
ing caliper in vise. Excessive vise pressure will
cause bore distortion.
(4) Mount the caliper in a vise equipped with pro-
tective jaws.
(5) Remove the piston dust boot from the caliper
and discard.
NOTE: Do not use a screw driver or other metal tool
for seal removal. Using such tools can scratch the
bore or leave burrs on the seal groove edges.
(6) Using a soft tool such as a plastic trim stick,
work the piston seal out of its groove in caliper pis-
ton bore (Fig. 39). Discard the old seal.
(7) Clean the piston bore and drilled passage ways
using alcohol or a suitable solvent. Wipe it dry using
only a lint-free cloth.
(8) Inspect the piston bore for scoring or pitting.
Bores that show light scratches or corrosion can usu-
ally be cleared of the light scratches or corrosion
using crocus cloth.
Fig. 38 Removing/Installing Caliper
1 - LIFT THIS END OF CALIPER AWAY FROM ADAPTER FIRST
2 - DISC BRAKE CALIPER
3 - ADAPTER ABUTMENT
4 - OUTBOARD BRAKE SHOE HOLD DOWN CLIP
5 - OUTBOARD BRAKE SHOE
6 - ROTOR
7 - ADAPTER
Fig. 39 Removing Piston Seal
1 - PLASTIC TRIM STICK
2 - CALIPER
3 - PISTON SEAL GROOVE
4 - PISTON SEAL
RSBRAKES - BASE5-27
DISC BRAKE CALIPERS - REAR (Continued)
ProCarManuals.com

DIAGNOSIS AND TESTING - POWER BRAKE
BOOSTER
BASIC TEST
(1) With engine off, depress and release the brake
pedal several times to purge all vacuum from the
power brake booster.
(2) Depress and hold the pedal with light effort (15
to 25 lbs. pressure), then start the engine.
The pedal should fall slightly, then hold. Less effort
should be needed to apply the pedal at this time. If
the pedal fell as indicated, perform the VACUUM
LEAK TEST listed after the BASIC TEST. If the
pedal did not fall, continue on with this BASIC TEST.
(3) Disconnect the vacuum hose on the vacuum
check valve, then place a vacuum gauge in line
between the vacuum hose and the valve.
(4) Start the engine.
(5) When the engine is at warm operating temper-
ature, allow it to idle and check the vacuum at the
gauge.
If the vacuum supply is 12 inches Hg (40.5 kPa) or
more, the power brake booster is defective and must
be replaced. If the vacuum supply is below 12 inches
Hg, continue on with this BASIC TEST.
(6) Shut off the engine.
(7) Connect the vacuum gauge to the vacuum ref-
erence port on the engine intake manifold.
(8) Start the engine and observe the vacuum
gauge.
If the vacuum is still low, check the engine tune
and repair as necessary. If the vacuum is above 12
inches Hg, the hose or check valve to the booster has
a restriction or leak.
Once an adequate vacuum supply is obtained,
repeat the BASIC TEST.
VACUUM LEAK TEST
(1) Disconnect the vacuum hose on the vacuum
check valve, then place a vacuum gauge in line
between the vacuum hose and the valve.
(2) Start the engine.
(3) Allow the engine to warm up to normal operat-
ing temperature and engine idle.
(4) Using vacuum line pliers, close off the vacuum
supply hose near the booster, but before the vacuum
gauge, then observe the vacuum gauge.
If the vacuum drop exceeds 1.0 inch Hg (3.3 kPa)
in one minute, repeat the above steps to confirm the
reading. The vacuum loss should be less than 1.0
inch Hg in one minute time span. If the loss is more
than 1.0 inch Hg, replace the power brake booster. If
it is not, continue on with this test.
(5) Remove the pliers from the hose temporarily.
(6) Apply light effort (approximately 15 lbs. of
force) to the brake pedal and hold the pedal steady.Do not move the pedal once the pressure is applied
or the test results may vary.
(7) Have an assistant reattach the vacuum line
pliers to the vacuum supply hose.
(8) Allow 5 seconds for stabilization, then observe
the vacuum gauge.
If the vacuum drop exceeds 3.0 inches Hg (10 kPa)
in 15 seconds, repeat the above steps to confirm the
reading. The vacuum loss should be less than 3.0
inches Hg in 15 seconds time span. If the loss is
more than 3.0 inches Hg, replace the power brake
booster. If it is not, the booster is not defective.
(9) Remove the pliers and vacuum gauge.
REMOVAL - POWER BRAKE BOOSTER
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.
(1) With engine not running, pump the brake
pedal until a firm pedal is achieved (4-5 strokes).
(2) Remove negative battery cable terminal from
battery.
(3) Remove positive battery cable terminal from
battery.
(4) Remove battery thermal guard shield.
(5) Remove battery clamp, nut and battery from
the battery tray.
(6) Remove screw securing engine coolant filler
tube to battery tray.
(7) If the vehicle is equipped with speed control,
disconnect the vacuum hose at the vacuum tank built
into the battery tray.
(8) Remove the two nuts and one bolt securing bat-
tery tray in place. Remove battery tray.
(9) If vehicle is equipped with speed control:
(a) Disconnect wiring harness connector from
the speed control servo.
(b) Remove the two servo mounting nuts.
(c) Lay speed control servo off to the side, out of
the way.
(10) Remove the wiper module (unit). (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/WIPER MOD-
ULE - REMOVAL)
(11) Disconnect wiring harness connector from
brake fluid level switch in master cylinder fluid res-
ervoir (Fig. 54).
5 - 38 BRAKES - BASERS
POWER BRAKE BOOSTER (Continued)
ProCarManuals.com

(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. 57).
(22) Slide power brake booster forward and remove
through engine compartment (Fig. 58).
CAUTION: Do not attempt to disassemble the power
brake vacuum booster it is serviced ONLY as a
complete assembly.INSTALLATION - POWER BRAKE BOOSTER
(1) Position power brake booster on dash panel
using the reverse procedure of its removal (Fig. 58).
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. 57). 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. 59).
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.
Fig. 57 BOOSTER MOUNTING
1 - DASH BRACKET
2 - POWER BRAKE BOOSTER
3 - BRAKE PEDAL ASSEMBLY
Fig. 58 BOOSTER REMOVAL/INSTALLATION
Fig. 59 Retaining Pin Installed On Brake Pedal Pin
1 - BRAKE PEDAL
2 - RETAINING CLIP
3 - BOOSTER INPUT ROD
5 - 40 BRAKES - BASERS
POWER BRAKE BOOSTER (Continued)
ProCarManuals.com

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.
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 thevehicle through the movement of the proportioning
valve actuator lever (Fig. 61). 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 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.
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.
Fig. 61 HEIGHT SENSING PROPORTIONING VALVE
1 - PROPORTIONING VALVE
2 - ACTUATOR LEVER
3 - AXLE BRACKET
4 - REAR AXLE
5 - 42 BRAKES - BASERS
PROPORTIONING VALVE (Continued)
ProCarManuals.com

(4) Bleed the brake system thoroughly to ensure
that all air has been expelled from the hydraulic sys-
tem. (Refer to 5 - BRAKES - BASE - STANDARD
PROCEDURE).
(5) Lower the vehicle to the ground.
(6) Road test the vehicle to verify proper operation
of the brake system.
ROTORS
DIAGNOSIS AND TESTING - BRAKE ROTOR
Any servicing of the rotor requires extreme care to
maintain the rotor within service tolerances to
ensure proper brake action.
Excessive runout or wobble in a rotor can increase
pedal travel due to piston knock-back. This increases
guide pin sleeve wear due to the tendency of the cal-
iper to follow the rotor wobble.
When diagnosing a brake noise or pulsation, the
machined disc braking surface should be checked and
inspected.
BRAKING SURFACE INSPECTION
Light braking surface scoring and wear is accept-
able. If heavy scoring or warping is evident, the rotor
must be refaced or replaced. (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/ROTORS - STAN-
DARD PROCEDURE).
Excessive wear and scoring of the rotor can cause
improper lining contact on the rotor's braking sur-
face. If the ridges on the rotor are not removed beforenew brake shoes are installed, improper wear of the
shoes will result.
If a vehicle has not been driven for a period of
time, the rotor's braking surface will rust in the
areas not covered by the brake shoes at that time.
Once the vehicle is driven, noise and chatter from
the disc brakes can result when the brakes are
applied.
Some discoloration or wear of the rotor surface is
normal and does not require resurfacing when lin-
ings are replaced. If cracks or burned spots are evi-
dent, the rotor must be replaced.
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 machining the rotor
will cause its thickness to fall below specifications.
CAUTION: Do not machine the rotor if it will cause
the rotor to fall below minimum thickness.
Minimum thickness specifications are cast on the
rotor's unmachined surface (Fig. 63). Limits can also
be found in the table at the end of this brake rotor
information.
ROTOR THICKNESS VARIATION
Thickness variation in a rotor's braking surface
can result in pedal pulsation, chatter and surge. This
can also be caused by excessive runout in the rotor or
the hub.
Rotor thickness variation measurements should be
made in conjunction with measuring runout. Mea-
sure thickness of the brake rotor at 12 equal points
around the rotor braking surface with a micrometer
at a radius approximately 25 mm (1 inch) from edge
of rotor (Fig. 64). If thickness measurements vary by
Fig. 62 PROPORTIONING VALVE MOUNTING
1 - LEFT REAR OUTLET TUBE
2 - RIGHT REAR OUTLET TUBE
3 - RIGHT REAR INLET TUBE
4 - MOUNTING BOLTS
5 - LEFT REAR INLET TUBE
Fig. 63 Minimum Brake Rotor Thickness Markings
(Typical)
1 - ROTOR MINIMUM THICKNESS MARKING
2 - ROTOR
5 - 44 BRAKES - BASERS
PROPORTIONING VALVE (Continued)
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