Suspension Air System; Inspection; Air Line Test; Suspension Height Adjustment - PREVOST H3-41 Maintenance Manual

SECTION 16 : SUSPENSION
Refer to section 2.3 for more information
regarding radius rods.
6

SUSPENSION AIR SYSTEM

The suspension air system has its own air
reservoir (accessory tank) which is located in the
reclining bumper compartment. Pressurized air
from the main tank (wet tank) flows through a
pressure protection
accessory air tank and through an air filter which
is located in front service compartment.
The pressure protection valve (PR-4) is mounted
to the supply port of the tank. This valve controls
the pressure at which compressed air is
delivered to the accessory air tank. The valve
remains closed until a preset pressure is
reached (approximately 70 psi (485 kPa)). It then
opens and passes air out the delivery port.
The main use for this valve is to protect the main
air system by ensuring at all times a sufficient air
pressure in the main system (i.e. air delivered to
the accessories will be shut off in case of a
decrease in pressure). Maintenance and repair
information on the pressure protection valve is
supplied in the applicable booklet, annexed to
Section 12, "Brakes and Air System" under
reference number SD-03-2010.
WARNING
Depressurize parts prior to removal.
6.1

INSPECTION

The following inspection should be performed at
established service
Performing these
substandard performance to be discovered
before the condition becomes bad enough to
cause operator complaints or failure during
operation.
1. Visually inspect the suspension air lines for
evidence of chafing on metal parts or other
damage.
2. Visually inspect the air springs for cracks,
abrasion or other damage.
3. Replace any parts found to be damaged.
46 PA1621 Maintenance Manual All Series | Section revised October 2018
valve (PR-4), to the
inspection periods.
procedures will allow
6.2

AIR LINE TEST

With the main air system at normal operating
pressure, coat all
connections and air spring mountings with a
solution of soap and water.
produce soap bubbles. Any leak found must be
corrected as no air leakage is permissible.
7

SUSPENSION HEIGHT ADJUSTMENT

The flow of pressurized air from the accessory
air tank to the air springs is controlled by three
height control valves. These valves are mounted
to the subframe and connected to the axles
through an arm and link connection. This
connection allows the valves to apportion air
pressure in the springs to the vehicle load,
maintaining normal ride height.
To adjust suspension
Maintenance Information
SUSPENSION HEIGHT ADJUSTMENT USING
HEIGHT CONTROL VALVES included after
Section 16 in this Maintenance Manual.
7.1

NORMAL RIDE HEIGHT

The normal ride height is obtained by measuring
and adjusting air spring height of front and rear
suspension.
FRONT SUSPENSION (I-BEAM AXLE)
2 air springs
X = 11 ¾ ± ¼ inch (297 ± 6 mm)
INDEPENDENT FRONT SUSPENSION (IFS)
2 air springs
X = 12 7/8 ± 1/4 inch (327 ± 6 mm)
suspension air line
Air leakage will
height, refer to
MI16-14