(3) During roa d test , make nor mal and fir m brake
st ops in 25-40 mph ra nge. Note fa ulty br ake opera-
tion su ch as low peda l, hard pedal, fade, peda l pulsa-
tion, pu ll, grab, drag, noise, etc.
(4) Attem pt t o stop t he vehicle with t he parking
brake on ly a nd note gra b, drag, noise, etc.
PEDAL FALLS AWA Y
A br ake pedal tha t fa lls awa y un der steady foot
pr essu re is gener ally th e result of a system lea k. Th e
leak point could be a t a br ake line, fitting, hose, or
caliper/wh eel cylinder. If leakage is severe, fluid will
be evident a t or aroun d t he leaking componen t.
In tern al lea kage (sea l by-pass) in the master cylin -
der caused by wor n or damaged pist on cups, may
also be the pr oblem cause.
An interna l leak in the ABS or RWAL system may
also be the pr oblem with no ph ysical evidence.
LOW PEDAL
If a low pedal is experienced, pump the peda l sev-
eral tim es. If the peda l comes ba ck up wor n linings,
rotors, dru ms, or rea r brakes out of a djustm ent ar e
the most likely causes. The proper cour se of a ction is
to inspect and repla ce all worn com ponent a nd make
the pr oper a djust ments.
SPONGY PEDAL
A spongy peda l is most oft en caused by air in the
system. However, th in br ake drums or substandar d
brake lines a nd hoses can a lso cau se a spongy peda l.
The pr oper course of a ction is to bleed t he syst em,
and replace thin dr ums an d subst andar d qu ality
brake h oses if suspected.
HARD PEDAL OR HIGH PEDAL EFFORT
A h ard peda l or high pedal effor t may be due to
lin ing t hat is water soaked, contamin ated, glazed, or
badly wor n. The power booster or check valve could
also be faulty.
PEDAL PULSATION
Pedal pu lsation is caused by com pon ents that are
loose, or beyond tolera nce limits.
The primar y cause of pulsation are disc br ake
rotors with excessive later al ru nout or thickn ess vari-
ation, or ou t of round bra ke drum s. Other causes are
loose wheel bea rings or calipers and worn, dam aged
tires.
NOTE: Some pedal pulsation may be felt during
ABS activation.
BRAKE DRAG
Brake drag occurs when th e lining is in con st ant
contact with the rotor or dr um. Dra g can occur at one
wheel, all wh eels, fronts only, or rears on ly.
Drag is a produ ct of incomplete brake shoe relea se.
Drag can be minor or severe enough to overh eat th e
lin ings, rotor s a nd drum s.
Minor drag will usu ally cau se slight su rface char-
ring of t he lining. It can a lso generate h ard spots in
rotors and dru ms from the overh eat-cool down pro-
cess. In most cases, the rotors, drums, wh eels an d
tires a re quite wa rm to the touch after the vehicle is
st opped.
Severe dr ag can char the br ake lin ing a ll the way
through. It can also distort and score rotors and
dr ums to the point of replacem ent. Th e wheels, tir es
and br ake com pon ents will be extremely hot . In
severe cases, th e lining m ay gen erat e sm oke as it
chars fr om overhea tin g.
Common ca uses of bra ke dr ag a re:
• Seized or improper ly adjusted parkin g br ake
cables.
• Loose/worn wheel bearing.
• Seized ca liper or wh eel cylin der piston.
• Ca liper binding on corroded bu sh ings or rusted
slide surfaces.
• Loose caliper moun tin g.
• Dr um brake shoes bindin g on wor n/dama ged
su pport plates.
• Mis-assembled compon ents.
• Lon g booster output r od.
If brake drag occu rs a t all wheels, the problem
may be rela ted t o a blocked m aster cylinder return
por t, or faulty power booster (binds-does not release).
BRAKE FADE
Brake fade is usually a pr odu ct of overheating
caused by brake dra g. However, brake overh eating
and resultin g fa de ca n also be caused by riding the
brake pedal, making repeated high deceleration stops
in a sh ort t ime spa n, or constant braking on steep
mountain roa ds. Refer to the Brake Drag information
in this section for ca uses.
BRAKE PULL
Front br ake pull condit ion could result from:
• Con taminat ed lining in one caliper
• Seized ca liper pist on
• Binding ca liper
• Loose caliper
• Ru st y caliper slide surfaces
• Improper br ake pads
• Da maged rotor
A worn , da maged wheel bearing or su spen sion
component are further causes of pull. A dama ged
front tire (bruised, ply separation ) can also cause
pull.
A common and frequen tly m isdiagnosed pu ll condi-
tion is where direct ion of pu ll changes aft er a few
st ops. The cause is a com bina tion of brake dr ag fol-
lowed by fade a t one of t he bra ke units.
VA BRAKES - BASE 5 - 3
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