As th e dr agging brake overhea ts, efficiency is so
reduced th at fade occurs. Sin ce th e opposite br ake
unit is st ill functioning normally, it s bra king effect is
magnified. This ca uses pull t o switch direction in
favor of t he nor mally funct ioning brake unit.
An a ddition al point when diagn osing a ch ange in
pu ll condition concer ns br ake cool down. Remember
that pull will return t o the original direction, if the
dr agging brake unit is a llowed to cool down (an d is
not seriously dama ged).
REAR BRAKE GRAB OR PULL
Rear grab or pu ll is usu ally caused by improperly
adju st ed or seized pa rking brake cables, contami-
nated lining, bent or bin ding shoes and su pport
plates, or impr oper ly assembled components. This is
pa rticula rly true when only one r ear wheel is
involved. However, wh en both rear wheels are
affected, th e ma st er cylin der or proport ioning va lve
could be at fau lt.
BRAKES DO NOT HOLD AFTER DRIVING THROUGH DEEP
WATER PUDDLES
This condition is gener ally caused by wa ter soaked
lin ing. If the lining is only wet, it can be dried by
dr iving wit h the brakes very lightly applied for a
mile or two. However, if th e lining is both soaked and
dirt cont aminat ed, clea ning and/or replacem ent will
be necessa ry.
BRAKE LINING CONTAMINATION
Brake lining contamination is mostly a pr odu ct of
leaking calipers or worn sea ls, driving thr ough deep
water puddles, or l ining that has become cover ed
with grea se and grit during r epair. Cont aminat ed lin -
ing should be replaced to avoid fu rther br ake prob-
lems .
WHEEL AND TIRE PROBLEMS
Som e condition s att ribu ted to brake component s
may actu ally be caused by a wheel or tire pr oblem.
A damaged wheel can cause shudder, vibra tion a nd
pu ll. A wor n or damaged tir e can also cau se pu ll.
Severely worn tires with very little tr ead left ca n
pr odu ce a gra b-like condition as the tir e loses a nd
recovers traction. Flat-spotted tires ca n cau se vibra-
tion and generate sh udder dur ing bra ke operat ion. A
tire with inter nal da mage such as a sever e bruise,
cut, or ply separ ation can cause pu ll a nd vibration.
BRAKE NOISES
Som e brake noise is common with rea r dr um
brakes an d on some disc brakes du ring the first few
st ops aft er a vehicle has been par ked ov ernight or
st ored. This is primarily due to th e formation of t race
corrosion (ligh t rust) on metal su rfaces. This light
corrosion is typically clea red from the metal surfaces
after a few brake applications causing t he noise to
subside.
BRAKE SQUEAK / SQUEAL
Brake squea k or squeal m ay be due t o linings th at
are wet or contaminated with brake fluid, grease, or
oil. Glazed linin gs an d rotors with hard spots can
also con tribute t o squea k. Dirt an d foreign ma terial
embedded in th e brake lining will also cause squea k/
squeal.
A very loud squeak or squeal is fr equen tly a sign of
severely worn brake lining. If the lining has worn
through t o the br ake pads i n spot s, met al-t o-meta l
contact occurs. If the condition is allowed t o cont inue,
rotors can become so scored tha t replacem ent is nec-
ess a r y.
BRAKE CHATTER
Brake chatter is usua lly caused by loose or worn
components, or glazed/bur nt lining. Rotors with hard
spots can also cont ribu te to cha tter. Addit iona l causes
of chatter are out-of-tolerance rotors, brake lin ing not
securely at tached to t he shoes, loose wheel bearings
and contaminated brake lining.
THUMP / CLUNK NOISE
Thum ping or clunk noises dur ing br aking a re fre-
qu en t ly not caused by br ake component s. In many
cases, such noises a re ca used by loose or da maged
st eering, su spen sion, or engine components. However,
calipers that bind on th e slide surfa ces can gener ate
a thump or clunk noise.
STAN DARD PROCEDU RE
STANDARD PROCEDURE - MANUAL BLEEDING
Use approved br ake fluid (Refer t o LUBRICATION
& MAINTENANCE /FLUID TYPES - DESCRIP-
TION). Use fresh, clea n fluid fr om a sealed conta iner
at all times.
(1) Remove reser voir filler caps and fill reservoir.
(2) If calipers, or wheel cylin ders were overha uled,
open all caliper and wheel cylinder bleed screws.
Then close each bleed screw as fluid sta rts to drip
from it. Top off master cylinder reservoir once more
before pr oceeding.
(3) Attach one end of bleed hose to bleed screw
and insert opposit e end in glass contain er par tia lly
filled with brake fluid (Fig. 1). Be sur e end of bleed
hose is immersed in fluid.
5-4 BRAKES- BASE VA
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