PA1621 Maintenance Manual All Series | January 2017
2 DESCRIPTION
The vehicle is provided with an air suspension
system. The system consists of air springs,
height control valves, radius rods, sway bars,
tripod and shock absorbers (Figure 1 to Figure
7). The system operation is fully automatic and
maintains a constant vehicle height regardless of
load, or load distribution.
The vehicle can also be equipped with systems
such as:
• Front Kneeling + Front High-Buoy;
• Front Kneeling + Full High-Buoy;
• Front Kneeling + Front High-Buoy and Low-
Buoy Combination;
• Front Kneeling + Full High-Buoy and Low-
Buoy Combination;
For a description of each of these systems, refer
to the appropriate heading in this section
3 FRONT I-BEAM AXLE SUSPENSION
FIGURE 1: FRONT I-BEAM AXLE SUSPENSION 16105
3.1 AIR SPRINGS
The air springs are made from a special
compound rubber molded to the proper contour
and dimensions. The entire vertical load of the
vehicle is supported by these springs. Each of
the three axles is provided with air springs that
are attached to the subframe and to the axles.
3.1.1 Inspection
1. Check operation of bellows.
2. Visually inspect bellows for evidence of
cracks, punctures, deterioration, or chafing.
Replace the bellows if any damage is
evident.
3. With the primary air system at normal
operating pressure (122 - 140 psi (841 - 965
kPa)), coat all suspension air line
connections and bellows mounting areas
with a water and soap solution. Bubbles will
indicate an air leak, and none is permissible.
Repair or replace defective parts.
FIGURE 2: AIR SPRING 16052
If air spring is removed from vehicle, bellows
can be lightly inflated and submerged in water
to detect any leakage. If any leakage is
detected, replace bellows.
WARNING
To prevent personal injury, do not apply more
than 10 psi (69 kPa) of air pressure to the
uninstalled air spring.
3.1.2 Removal
Front suspension air springs can be removed
without removing the entire axle assembly.
1. Safely support vehicle at the recommended
body jacking points. To gain access to a
given air spring, the corresponding wheel
can be removed as follows:
a) Jack vehicle until the tire clears the
ground, and place safety supports
underneath body.
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