FORD 1998 Expedition - Manual (Page 105)

BRAKES
Your service brakes are self-adjusting. Refer to the scheduled
maintenance guide for scheduled maintenance.
Occasional brake noise is normal and often does not indicate a
performance concern with the vehicle’s brake system. In normal
operation, automotive brake systems may emit occasional or intermittent
squeal or groan noises when the brakes are applied. Such noises are
usually heard during the first few brake applications in the morning;
however, they may be heard at any time while braking and can be
aggravated by environmental conditions such as cold, heat, moisture,
road dust, salt or mud. If a “metal-to-metal,” “continuous grinding” or
“continuous squeal” sound is present while braking, the brake linings
may be worn-out and should be inspected by a qualified service
technician.
Anti-lock brake system (ABS)
On vehicles equipped with an anti-lock braking system (ABS), a noise
from the hydraulic pump motor and pulsation in the pedal may be
observed during ABS braking events. Pedal pulsation coupled with noise
while braking under panic conditions or on loose gravel, bumps, wet or
snowy roads is normal and indicates proper functioning of the vehicle’s
anti-lock brake system. The ABS performs a self-check at 17 km/h (10
mph) after you start the engine and begin to drive away. A brief
mechanical noise may be heard during this test. This is normal. If a
malfunction is found, the ABS warning light will come on. If the vehicle
has continuous vibration or shudder in the steering wheel while braking,
the vehicle should be inspected by a qualified service technician.
The ABS operates by detecting the
onset of wheel lockup during brake
applications and compensating for
this tendency. The wheels are
prevented from locking even when
the brakes are firmly applied. The
accompanying illustration depicts
the advantage of an ABS equipped
vehicle (on bottom) to a non-ABS
equipped vehicle (on top) during
hard braking with loss of front braking traction.
Driving
105