SECTION 16: SUSPENSION
20
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Section 16 revised April 2019)
clearance should be 11 11/16” ± ¼“ (297 ± 6
mm).
NOTE
The measurement should be taken from
underneath the upper air spring support on
subframe to top of the lower air spring support
on axle (refer to Figure 17 for more details). If
adjustment is required, begin with the drive
axle.
2. Loosen the clamp on the height control
valve rubber coupling and bring it up or
down (Figure 21).
NOTE
Allow suspension to stabilize before taking
reading.
When the desired height is obtained, tighten
clamp.
Rear air spring clearance
1. With the vehicle at normal operating air
pressure [122 - 140 psi], measure air spring
clearance. This clearance should be as per
Figure 18 and Figure 19.
NOTE
The measurement should be taken from
underneath the upper air spring support on
subframe to top of the lower air spring support
on axle.
2. Loosen the clamp on the height control
valve rubber coupling and bring it up or
down (Figure 21).
NOTE
Allow suspension to stabilize before taking
reading.
FIGURE 21: REAR HEIGHT CONTROL VALVE
16093
When the desired height is obtained, tighten
clamp.
7. HEIGHT
CONTROL
VALVE
The height control valves automatically add air
to, or release air from air springs to maintain
constant suspension height regardless of load,
or load distribution. Each valve adjusts
independently according to the following
conditions:
Loading Position
As the load increases and lowers the vehicle
body, the overtravel lever commands the height
control valve to add air to air springs.
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.
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.
7.1 MAINTENANCE
The height control valve requires no periodic
maintenance. Height control valve linkage
operates on rubber bushings and no lubrication
should be attempted at this location. Inspect the
valve for loose joints, air leaks and worn
bushings.
7.2 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.
