219
2008 IMPERIAL
CHASSIS INFORMATION — 10
Inspect
the
Outside Diameter (OD)
of
the air springs. Check for irregular wear,
heat cracking or chaf
fi
ng.
Inspect
air lines to ensure contact does
not exist between air line and OD of the
air springs. Air lines can rub a hole in an
air spring very quickly.
Ensure there is suf
fi
cient clearance
around the complete circumference
of the air spring while at maximum
diameter.
Inspect
the OD of piston for buildup of
foreign materials. On a reversible sleeve
style air spring, the piston is the bottom
component of the air spring.
The correct ride height should be
maintained. All motorhomes with air
springs have a speci
fi
ed ride height
established by the manufacturer. This
height should be maintained within ¼
inch. This dimension can be checked
with the motorhome loaded or empty.
The leveling valves (or height control
valves) assist in ensuring the total air
spring system works as required. Clean,
inspect
and replace if necessary.
Make sure to check shock absorbers for
leaking hydraulic oil and worn or broken
end connectors. If a broken shock is
found, replace it immediately. The shock
absorber will normally limit the rebound
of an air spring and keep it from over
extending.
Check the tightness of all mounting
hardware (nuts and bolts). If loose,
tighten.
DO NOT
over-tighten.
Cleaning:
The approved cleaning method is to use soap
and water, methyl alcohol, ethyl alcohol or
isopropyl alcohol. Unapproved cleaning methods
include all organic solvents, open
fl
ames,
abrasive and direct pressurized steam cleaning.
HEIGHT CONTROL VALVES
Height Control Valves (HCV)
in
fl
ate or
de
fl
ate air springs to maintain proper suspension
height throughout the load range. Two Height
Control Valves are installed at the rear drive
axle to control rear suspension height and left
or right tilt of the motorhome. A separate HCV
is installed to control front suspension height.
The three HCVs mount to the main frame of the
motorhome, above the axles, with a linkage rod
connecting the valve to the axle.
Actuating components inside of the valves
are oil dampened to reduce valve reaction to
momentary suspension bounce and rebound.
When a constant suspension change occurs,
such as a load change or weight transfer through
a sustained corner, the valve reacts by adding or
purging air from the air springs as needed.
The air springs mount between the axle H-
frame assembly and the two main frame rails.
Air spring support plates mount to the main
frame and the H-frame. There is a speci
fi
ed
distance the air spring must maintain between
the mounting plates. Other than speci
fi
ed
distance between the plates will compromise
ride quality and handling, and affect shock
absorber travel, drive shaft angle, as well as
various other running gear components.
BRAKE SYSTEMS
Air Brakes
The air brake system on the motorhome differs
from a conventional automotive hydraulic braking
system and should be treated differently. Proper
maintenance and lubrication are the keys to keeping
the air brake system in proper working order.
The air system supplies air to the foot brake
or treadle valve. Pushing down on the treadle
valve supplies an air charge signal to a sealed
brake chamber, consisting of a spring and air
bladder. The air charge signal pushes on the
bladder and extends a threaded rod connected to
the automatic slack adjuster, which rotates the
S-cam and expands the shoes against the drum.
Air disc brakes follow much the same principle,
with the exception of the threaded rod directly
activating calipers.
Consideration needs to be given to stopping
distances and air system pressures. The
motorhome requires longer stopping distances.
Each brake application uses air from the
air system, and engine speed is directly
proportional to how fast that air system is
replenished. Prepare for downhill grades. It
may be necessary to select a lower gear and/or
use the engine brake. Use individual, short
brake applications down long hills rather than
riding the brakes. This will extend the life of
the brake lining. Avoid overheating the brakes.
Hot brakes have less stopping power. When
maneuvering the motorhome around small
areas, or backing into spaces, several individual
brake applications might be made. Watch the
air gauge. When preparing to back into a space,
swing the motorhome so it is aligned with the
parking slot before backing up.
