PREVENTIVE MAINTENANCE AIR SYSTEM
Regional Haul
(R05/10) Y53-6033 – 195 –
CAUTION: When draining the engine cooling
system is required, to prevent damage from
freezing, the compressor must also be
drained at the cylinder head and block.
Engine damage could occur if the cooling
system is not periodically drained and main-
tained. See “
Engine Cooling System,” Page 175,
and the Maintenance Manual for further infor-
mation.
Air Dryer
WARNING! Use of incorrect air dryer could
cause air system failure, leading to loss of
vehicle control and serious personal injury or
death. If your vehicle is equipped with a Ben-
dix AD-IS air dryer, it is important that future
replacements be identical or similar in design.
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 of a wet tank, forward dry
tank, and rear dry tank. The dry tanks have a single-check
valve in the tank inlet. The check valves prevent a com-
plete 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: A small amount of oil in the system may 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 25,000 miles/40,000 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 res-
ervoir 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 high-
way vehicle. This may be due to accessory air
demands or some other unusual air requirement that
doesn’t allow the compressor to load/unload in a nor-
mal 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
