Exhaust Brake - freightliner S2 Operator's Manual

Hydraulic and Air Brake Systems
the ATC system automatically limits wheel spin dur-
ing reduced-traction situations. In normal braking ap-
plications, the standard air brake system is in effect.
During reduced-traction situations, the ATC solenoid
valve controls air pressure to the modulator valves
and they in turn increase, hold, or reduce pressure to
the appropriate brake chambers to provide better
traction whenever wheel spin occurs.
When the ATC system is in the NORMAL mode, it
will apply gentle braking to the spinning wheel, to
feed power to the wheel(s) with better traction. If
both wheels are spinning, the system will signal the
engine to reduce power.
ATC may include a deep snow and mud option to
increase available traction on extra soft surfaces like
snow, mud, or gravel. If so equipped, a momentary
contact rocker switch labeled ATC will be located on
the dash. Pressing the switch will temporarily allow
more wheel spin. The activation of the deep snow
and mud option is indicated by a flashing WHEEL
SPIN lamp. Pressing the switch again will cycle the
system back to normal operation.
NOTICE
The deep snow and mud option is intended to be
used under specific slippery conditions that re-
quire momentary increased wheel spin. Using
this option for an extended period of time may
damage the vehicle brake system.
After the ignition switch is turned on, the ABS indica-
tor light and the WHEEL SPIN indicator light illumi-
nate for about three seconds. After three seconds,
the warning lights go out if all of the ABS compo-
nents are working.
During vehicle operation, solid illumination of the
ABS light indicates a problem with the vehicle ABS.
Repair the ABS immediately to ensure full braking
capability.
If equipped with ATC, an amber WHEEL SPIN indica-
tor light illuminates if one of the drive wheels spins
during acceleration. When the light illuminates, par-
tially release the throttle pedal to stop the spinning
wheel. The light goes out when the wheel stops spin-
ning.
If slippery road conditions continue, turn on the differ-
ential lock switch. See Chapter 11
structions.
13.5
for axle switch in-
NOTICE
Do not turn the differential lock switch on while
the WHEEL SPIN indicator light is on. To do so
could damage the rear axle.
Automatic Slack Adjusters
NOTICE
Manually adjusting an automatic slack adjuster to
bring the pushrod stroke within legal limits is
likely masking a mechanical problem. Adjustment
is not repairing. In fact, continual adjustment of
automatic slack adjusters may result in prema-
ture wear of the adjuster itself. Further, the im-
proper adjustment of some automatic slack ad-
justers may cause internal damage to the
adjuster, thereby preventing it from properly
functioning.
Automatic slack adjusters should never be manually
adjusted except during routine maintenance of the
foundation brakes (e.g., replacing shoes), during
slack adjuster installation, or in an emergency situa-
tion.
When the brake pushrod stroke exceeds the legal
brake adjustment limit on a vehicle, there is likely a
mechanical problem with the foundation brake com-
ponents or the adjuster is improperly installed.
Visit a repair facility as soon as possible when
brakes equipped with automatic slack adjusters are
determined to be out of adjustment.

Exhaust Brake

General Information
An exhaust brake is an optional auxiliary braking sys-
tem that assists, but does not replace, the service
brake system. The driver can use the exhaust brake,
in combination with the accelerator and clutch pedal
(if so equipped), to make maximum use of the ex-
haust brake in off-highway and mountain driving as
well as in traffic or high-speed highway driving.
The exhaust brake is controlled by a dash-mounted
rocker switch, shown in
vehicle when the accelerator is released.
To turn the exhaust brake on, press on the upper
part of the rocker switch. When the exhaust brake
Fig. 13.3, to help slow the