PREVOST GKN AXLES LIMITED KIRKSTALL DIVISION, Руководство по обслуживанию

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Section 16: SUPPLEMENT INFORMATION ON INDEPENDENT FRONT SUSPENSION (IFS)
16-30
9.1.2 Neutral Position
When vehicle body reaches the normal ride
height, the height control valve overtravel lever
reaches the "neutral" position and keeps both the
supply and exhaust ports closed to ensure normal
ride height is maintained. This condition remains
static until the vehicle load is altered.
9.1.3 Unloading Position
As the load decreases and raises the vehicle
body, the overtravel lever commands the height
control valve to release air from air springs.
9.2 Maintenance
The height control valve requires no periodic
maintenance. Height control valve linkage oper-
ates on rubber bushings and no lubrication should
be attempted at this location. Inspect the valve for
loose joints, air leaks and worn bushings.
9.2.1 Removal and Installation
Before disconnecting a height control valve air
line, securely support the vehicle by its jacking
points on the body, and place safety supports
underneath body. Refer to paragraph "16. Vehicle
Jacking Points" in Section 18, "Body".
1. Exhaust air from air system by opening all air
tank drain cocks. Remove height control
valves.
2. Disconnect overtravel lever from link and pull
down lever to exhaust remaining air from air
springs.
3. Disconnect air supply and delivery lines from
the height control valve. Cover line ends with
tape to prevent entry of foreign matter.
4. Remove the nuts retaining the height control
valve to the mounting bracket, then remove
valve assembly.
Reverse removal procedure to replace height
control valve. After installation, check for leakage
using a soap and water solution.
10. "LEVEL-LOW" LEVELING
SYSTEM (IF APPLICABLE)
The purpose of the "level-low" leveling system is
to adjust suspension in three separate points
(front, rear right and rear left) in order to level
vehicle body. This system can be put into service
when the ignition key is turned to the "ON" posi-
tion, and must be used only when the parking
brake is applied. The "level-low" warning light on
the dashboard indicates that the push-button
shifter is not in the "DRIVE" position. Level low
system controls are located on L.H. side control
panel.
10.1 Principles of Operation
Refer to the systems pneumatic diagram
annexed at the end of this section.
11. AIR SYSTEM
The basic air system consists of an air compres-
sor, tanks, valves, filters and interconnecting lines
and hoses (refer to Section 12, "Brake and Air
System" for complete information). It provides a
means for braking, operating controls and acces-
sories, and suspension. An air system schematic
diagram is annexed at the end of this supplement
for better understanding of the system.
11.1 Air Tanks' Locations and
Functions
The air coming from the air dryer is first directed to
the wet air tank, then to the primary (for the pri-
mary brake system), secondary (for the secon-
dary brake system), and accessory (for the
pneumatic accessories) air tanks (Fig. 25).
In addition, an expansion air tank is installed in
series with each air spring.