Dodge RAM TRUCK 1500 1995 Service Manual page 178

5 - i SERVICE BRAKE DIAGNOSIS
B R
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 few
minutes. However, if the lining is thoroughly wet and
dirty, disassembly and cleaning will be necessary.
BRAKE NOISE
Squeak/Squeal
Factory installed brakelining is made from as­
bestos free materials. These materials have dif­
ferent operating characteristics than previous
brakelining material. Under certain conditions,
asbestos free lining may generate some squeak,
groan or chirp noise. This noise is considered
normal and does not indicate a problem. The
only time inspection is necessary, is when noise
becomes constant or when grinding, scraping
noises occur.
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 can 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 brakeshoes in spots, metal-to-metal
contact occurs. If the condition is allowed to continue,
rotors and drums can become so heavily scored that
replacement is necessary.
Thump/Clunk
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 pins, or slide surfaces,
can generate a thump or clunk noise. Worn out, im­
properly adjusted, or improperly assembled rear
brakeshoes can also produce a thump noise.
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.
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. Se­
verely worn tires with very little tread left can pro­
duce a grab-like condition as the tire loses and
recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe bruise
or ply separation can cause pull and vibration.
CONTAMINATED BRAKELINING
Contaminated brakelining will cause pull, noise,
grab, and will increase stopping distance. Road
splash and leaking caliper, wheel cylinder, or axle
seals are the primary causes.
Brakelining contaminated by water only can be sal­
vaged. The lining can either be air dried or dried us­
ing heat.
In cases where brakelining is contaminated by oil,
grease, or brake fluid, the lining should be replaced.
Replacement is especially necessary when fluids/lu­
bricants have actually soaked into the lining mate­
rial. However, grease or dirt that gets onto the lining
surface (from handling) during brake repairs, can be
cleaned off. Simply spray the lining surface clean
with Mopar brake cleaner.
BRAKE FLUID CONTAMINATION
The basic causes of brake fluid contamination are
threefold. The first involves allowing dirt, debris, or
other materials to enter the cylinder reservoir when
the cover is off. The second involves filling, or adding
non-recommended fluid to the system. A third cause
involves a loose reservoir, or mispositioned cover seal;
either condition will allow moisture and dirt to enter
the fluid.
Brake fluid contaminated with only dirt, or debris
usually retains a normal appearance. Generally, the
foreign material will remain suspended in the fluid
and be visible. The fluid and foreign material can be
removed from the reservoir with a suction gun but
only if the brakes have not been applied. If the
brakes are applied after contamination, system flush­
ing will be required. The master cylinder will also
have to be flushed or replaced if the contaminants
cannot be removed. Foreign material lodged in the
reservoir compensator/return ports can cause brake
drag by restricting fluid return after brake applica­
tion.
Brake fluid contaminated by a non-recommended
fluid, may appear highly discolored, milky, oily look­
ing, or foamy. In some cases, the fluid may even ap­
pear to contain sludge. However, be advised that
brake fluid will darken in time and occasion­
ally be cloudy in appearance. These are normal
conditions and should not be mistaken for con­
tamination.
If some type of oil has been added to the system,
the fluid will separate into distinct layers. To verify