Jeep Wrangler TJ. Manual — part 247
As the dragging brake overheats, efficiency is so
reduced that fade occurs. Since the opposite brake
unit is still functioning normally, its braking effect is
magnified. This causes pull to switch direction in
favor of the normally functioning brake unit.
An additional point when diagnosing a change in
pull condition concerns brake cool down. Remember
that pull will return to the original direction, if the
dragging brake unit is allowed to cool down (and is
not seriously damaged).
REAR BRAKE GRAB OR PULL
Rear grab or pull is usually caused by improperly
adjusted or seized parking brake cables, contami-
nated lining, bent or binding shoes and support
plates, or improperly assembled components. This is
particularly true when only one rear wheel is
involved. However, when both rear wheels are
affected, the master cylinder or proportioning valve
could be at fault.
BRAKES DO NOT HOLD AFTER DRIVING THROUGH DEEP
WATER PUDDLES
This condition is generally caused by water soaked
lining. If the lining is only wet, it can be dried by
driving with the brakes very lightly applied for a
mile or two. However, if the lining is both soaked and
dirt contaminated, cleaning and/or replacement will
be necessary.
BRAKE SQUEAK/SQUEAL
Brake squeak or squeal may be due to linings that
are wet or contaminated with brake fluid, grease, or
oil. Glazed linings and rotors with hard spots can
also contribute to squeak. Dirt and foreign material
embedded in the brake lining will also cause squeak/
squeal.
A very loud squeak or squeal is frequently a sign of
severely worn brake lining. If the lining has worn
through to the brake shoes in spots, metal-to-metal
contact occurs. If the condition is allowed to continue,
rotors and drums can become so scored that replace-
ment is necessary.
BRAKE CHATTER
Brake chatter is usually caused by loose or worn
components, or glazed/burnt lining. Rotors with hard
spots can also contribute to chatter. Additional causes
of chatter are out-of-tolerance rotors, brake lining not
securely attached to the shoes, loose wheel bearings
and contaminated brake lining.
THUMP/CLUNK NOISE
Thumping or clunk noises during braking are fre-
quently not caused by brake components. In many
cases, such noises are caused by loose or damaged
steering, suspension, or engine components. However,
calipers that bind on the slide surfaces can generate
a thump or clunk noise. In addition, worn out,
improperly adjusted, or improperly assembled rear
brake shoes can also produce a thump noise.
BRAKE LINING CONTAMINATION
Brake lining contamination is mostly a product of
leaking calipers or wheel cylinders, worn seals, driv-
ing through deep water puddles, or lining that has
become covered with grease and grit during repair.
Contaminated lining should be replaced to avoid fur-
ther brake problems.
WHEEL AND TIRE PROBLEMS
Some conditions attributed to brake components
may actually be caused by a wheel or tire problem.
A damaged wheel can cause shudder, vibration and
pull. A worn or damaged tire can also cause pull.
Severely worn tires with very little tread left can
produce a grab-like condition as the tire loses and
recovers traction. Flat-spotted tires can cause vibra-
tion and generate shudder during brake operation. A
tire with internal damage such as a severe bruise,
cut, or ply separation can cause pull and vibration.
STANDARD PROCEDURE
STANDARD PROCEDURE - MANUAL BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
(1) Remove reservoir filler caps and fill reservoir.
(2) If calipers, or wheel cylinders were overhauled,
open all caliper and wheel cylinder bleed screws.
Then close each bleed screw as fluid starts to drip
from it. Top off master cylinder reservoir once more
before proceeding.
(3) Attach one end of bleed hose to bleed screw
and insert opposite end in glass container partially
filled with brake fluid (Fig. 1). Be sure end of bleed
hose is immersed in fluid.
(4) Open up bleeder, then have a helper press
down the brake pedal. Once the pedal is down close
the bleeder. Repeat bleeding until fluid stream is
clear and free of bubbles. Then move to the next
wheel.
STANDARD PROCEDURE - PRESSURE
BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
TJ
BRAKES - BASE
5 - 5
BRAKES - BASE (Continued)
Follow the manufacturers instructions carefully
when using pressure equipment. Do not exceed the
tank manufacturers pressure recommendations. Gen-
erally, a tank pressure of 15-20 psi is sufficient for
bleeding.
Fill the bleeder tank with recommended fluid and
purge air from the tank lines before bleeding.
Do not pressure bleed without a proper master cyl-
inder adapter. The wrong adapter can lead to leak-
age, or drawing air back into the system. Use
adapter provided with the equipment or Adapter
6921.
SPECIFICATIONS
BRAKE COMPONENTS
SPECIFICATIONS
DESCRIPTION
SPECIFICATION
Disc Brake Caliper
Type
Sliding
Disc Brake Rotor
Type
Front
Ventilated
Disc Brake Rotor
Type
Rear
Solid
Disc Brake Rotor
Diameter
Front
279.4 x 23.876 mm (11 x
0.94 in.)
Disc Brake Rotor
Diameter
Rear
285 x 12 mm (11 x 0.472
in.)
Disc Brake Rotor
Ventilated
Front
Max. Runout
0.12 mm (0.005 in.)
Disc Brake Rotor
Solid
Rear
Max. Runout
0.102 mm (0.004 in)
Disc Brake Rotor
Ventilated
Front
Max. Thickness Variation
0.013 mm (0.0005 in.)
Disc Brake Rotor
Solid
Rear
Max Thickness Variation
0.018 mm (0.0007 in)
Disc Brake Rotor
Ventilated
Front
Min. Thickness
22.7 mm (0.8937 in.)
Disc Brake Rotor
Solid
Rear
Min. Thickness
11.00 mm (0.433 in.)
Brake Drum
Diameter
228.6 x 63.5 mm (9 x 2.5
in.)
Brake Booster
Type
Tandem Diaphragm
Fig. 1 Bleed Hose Setup
1 - BLEED HOSE
2 - FLUID CONTAINER PARTIALLY FILLED WITH FLUID
5 - 6
BRAKES - BASE
TJ
BRAKES - BASE (Continued)
TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION
N·m
Ft. Lbs.
In. Lbs.
Brake Pedal
Support Bolt
28
21
—
Brake Booster
Mounting Nuts
39
29
—
Master Cylinder
Mounting Nuts
17
13
—
Master Cylinder
Brake Lines
19
14
—
Combination Valve
Mounting Nuts
20
15
—
Combination Valve
Brake Lines
19
14
—
Caliper
Mounting Bolts
Front
15
11
—
Caliper
Mounting Bolts
Rear
25
—
220
Caliper
Brake Hose Banjo Bolt
Front
31
23
—
Caliper
Brake Hose Banjo Bolt
Rear
31
23
—
Wheel Cylinder
Mounting Bolts
10
7
—
Wheel Cylinder
Brake Line
16
12
—
Parking Brake
Lever Bolts
12
9
—
Parking Brake
Lever Bracket Bolts
12
9
—
Parking Brake
Cable Retainer Nut
1.5
—
14
TJ
BRAKES - BASE
5 - 7
BRAKES - BASE (Continued)
SPECIAL TOOLS
BASE BRAKES
BRAKE LINES
DESCRIPTION
Flexible rubber hose is used at both front brakes
and at the rear axle junction block. Double walled
steel tubing is used to connect the master cylinder to
the major hydraulic braking components and then to
the flexible rubber hoses. Double inverted style and
ISO style flares are used on the brake lines.
OPERATION
The hoses and lines transmit the brake fluid
hydraulic pressure to the calipers and or wheel cyl-
inders.
DIAGNOSIS AND TESTING - BRAKE LINE AND
HOSES
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
engine oil change, or whenever the vehicle is in for
service.
Inspect the hoses for surface cracking, scuffing, or
worn spots. Replace any brake hose immediately if
the fabric casing of the hose is exposed due to cracks
or abrasions.
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.
Factory replacement brake lines and hoses are rec-
ommended to ensure quality, correct length and supe-
rior fatigue life. Care should be taken to make sure
that brake line and hose mating surfaces are clean
and free from nicks and burrs. Also remember that
right and left brake hoses are not interchangeable.
Use new copper seal washers at all caliper connec-
tions. Be sure brake line connections are properly
made (not cross threaded) and tightened to recom-
mended torque.
STANDARD PROCEDURE
STANDARD PROCEDURE - BRAKE TUBE
FLARING
A preformed metal brake tube is recommended and
preferred for all repairs. However, double-wall steel
tube can be used for emergency repair when factory
replacement parts are not readily available.
Special bending tools are needed to avoid kinking
or twisting of metal brake tubes. Special flaring tools
are needed to make a double inverted flare or ISO
flare (Fig. 2).
STANDARD PROCEDURE - DOUBLE INVERTED
FLARING
A preformed metal brake tube is recommended and
preferred for all repairs. However, double-wall steel
tube can be used for emergency repair when factory
replacement parts are not readily available.
(1) Cut off damaged tube with Tubing Cutter.
(2) Ream cut edges of tubing to ensure proper
flare.
Installer Caliper Dust Boot C-4842
Handle C-4171
Adaptor Cap Pressure Bleeder 6921
5 - 8
BRAKES - BASE
TJ
BRAKES - BASE (Continued)
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