Performing Disc Brake Service on
ABS/TCS Equipped Vehicles
Many of the most common brake service procedures,
such as pad replacement, rotor service, and wheel bearing
replacement, are not affected by the presence of anti-lock
brakes (ABS) or traction controls (TCS). If the lining or friction
service replacement procedures involve the wheel speed
sensors, treat them gently, and recheck the gap where appli-
cable. Do not drop or hammer on the sensor rings, or use
them to pry on other components. Do not replace any system
hoses with standard (non-ABS) hoses. The higher pressures in
these systems can rupture a standard brake hose.
Checking Caliper and Pad Condition
Calipers are usually trouble free. However, they can
occasionally develop external brake fluid leaks or sticking
apply pistons. Hydraulic system problems were discussed
in Chapter 6. If there are no hydraulic system defects, the
caliper is usually not a source of problems. However, the
caliper should be checked for wear, cracks (especially at
the mounting points), and torn dust boots.
Observing the pad thickness and rotor condition is
the quickest way to determine whether the pads should be
replaced. Uneven wear between the inboard and outboard
pads is a sign of a sticking caliper piston or slide. Uneven
wear on one or both pads indicates that the caliper is mis-
aligned with the rotor.
Note in Figure 13-2 that pad thickness can be visually
checked by observing the pad lining thickness through
openings in the caliper. However, this provides only a gen-
eral idea of pad thickness. If the pads have a wear sensor,
you can check the amount of clearance between the sen-
sor and the rotor. If there is any doubt as to pad condition,
remove the caliper and check by measuring the pads
against specified minimum thickness. Note the condition
of the rotor. If the rotor is scored or appears to have been
overheated, the pads need replacement. Also, make sure
the wheel turns freely. If the wheel will not turn easily, the
caliper piston may be sticking, or there may be a problem
with the wheel bearings.
Front Caliper Removal and Pad
To remove the caliper, first raise and support the vehi-
cle in a safe manner. If a lift is not available, support the
vehicle at the frame with jackstands. Mark the wheel stud
closest to the tire valve stem with crayon to ensure the tire
is reinstalled in the same position. Then remove the tire
and rim.
If the pads are going to be replaced and no other
service is needed, it is not necessary to remove the caliper
hose. If the caliper uses an electrical pad wear sensor, dis-
connect the sensor electrical connector, Figure 13-3.
Use a small prybar, C-clamp, large adjustable pliers,
or other tool to lightly push the pads away from the rotor,
Figure 13-4. This will make caliper removal easier. If the
rotors and pads are badly grooved, the pads may need to
be moved back a considerable distance before they can be
On vehicles equipped with ABS systems, some man-
ufacturers recommend opening the bleeder screw to allow
fluid to escape, rather than pushing it back into the
hydraulic actuator and master cylinder. This minimizes the
chance of contamination, which could cause problems.
Check the service manual before proceeding.
Chapter 13 Disc Brake Service 211
Note: The following procedure is for
replacing the pads without overhauling the
caliper. If the caliper must be overhauled,
refer to Chapter 6.
Warning: Before proceeding, carefully check
the temperature of the hub and rotor
assembly. If the assembly feels hot, allow it
to cool, or use gloves to protect yourself from burns.
Figure 13-2. Brake pad thickness can be checked on this
assembly by looking through the inspection hole in the caliper.
I nspecti i on holeh l
Figure 13-3. A disc brake assembly which uses electric pad
wear sensors. (Land Rover)
Pad P sensor
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