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Cylinders &
Sensors
Master cylinder
The master cylinder is the heart of the system, pumping brake fluid when you
step on the pedal to apply the brakes. Brake fluid can pick up moisture and
contaminates and should be replaced about every 25,000 miles or at lining
replacement, whichever is sooner. A low fluid level may indicate a leak or
excessive brake lining wear. An immediate visual inspection of the brakes at
all four wheels, the linings, the hoses, and the steel brake lines is
recommended.
Caution: not all fluids are compatible. Use only the fluid type listed on
the lid of the master cylinder (example, DOT 3).
Calipers and wheel cylinders
The disc brake calipers and the drum brake wheel cylinders convert the
pressurized brake fluid into muscle power to apply the brakes. Visually
inspect for leaks around the rubber seals, and rebuild or replace if leaks
are detected.
ABS sensors and controller
ABS systems monitor wheel speed, tell the computerized controller when a
wheel or wheels are about to lock-up, and modulate the brakes. When the
brakes are being modulated (an ABS event), it is often possible to feel this
as a pulsing of the brake pedal. These systems are electronically
controlled, have extremely high reliability, and are self-diagnosing. The
amber ABS lamp comes on for a bulb check at start-up and will light if there
is a malfunction that shuts down the system. Some malfunctions, such as a
loose wire or an improperly adjusted wheel bearing, may be temporarily
self-correcting. The computer stores a record of these malfunctions in order
to advise the technician of any needed service.
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