Peterbilt Model 320 Operator's Manual after 8-07 - Peterbilt Motors ...

PART 8: MAINTENANCE AND SERVICE
Any deviation from the Bendix AD-IS type air dryer would
require changes to the vehicle air system. Some vehicles
use a dual air system consisting ofawettank,forwarddry
tank, and rear dry tank. The dry tanks have a single-check
valve in the tank inlet. The check valves prevent a complete
loss of air in the event of an air system failure (tank or
hose failure). This ensures a controlled stop (with reduced
braking capability). Other vehicles use a Bendix AD-IS air
dryer which eliminates the need for a wet tank and check
valves in the dry tanks.
NOTE:Asmallamountofoilinthesystemmay
be normal and should not, by itself, be considered
reason to replace a desiccant cartridge; oil-stained
desiccant can function adequately.
Every 900 operating hours or 30,000 miles/48,000 km or
3 months, check for moisture in the air brake system by
opening reservoirs, drain cocks, or valves and checking for
the presence of water. A tablespoon of water in a reservoir
would point to the need for a desiccant cartridge change.
However, the following should be considered first:
• Air usage is exceptionally high/abnormal for a highway
vehicle. This may be due to accessory air demands or
some other unusual air requirement that doesn’t allow
Clutch Adjustment
the compressor to load/unload in a normal fashion or
it may be due to excessive leaks in the air system.
• When more than a 30-degree F (17-degree C) range
of temperature occurs in one day, small amounts of
water can accumulate in the air brake system due to
condensation. Under these conditions, the presence
of small amounts of moisture is normal and should not
be considered as an indication that the dryer is not
performing properly.
• An outside air source may have been used to charge
the air system, in which case this air did not pass
through the drying bed.
Transmission And Drive Train
Clutch Adjustment
Clutchpedalfreetravelisusually13/4in.to2in.(34to51
mm). This should be your guide for determining whether
your truck needs clutch adjustment. Some vehicles have
automatic clutch adjustment. If yours doesn’t have this feature,
adjustment will have to be done by a trained certified
mechanic. Have the adjustment done before clutch pedal
free travel is reduced to the minimum allowable 1/2 in. (13
mm).
R(08/07) Y53-6015 – 165 –