58
Suspension
Suspension Troubleshooting (Continued)
†
Refer to the “Front Axle Troubleshooting” section later in this chapter for more information on vehicle
handling problems.
*The suspension air supply comes from the accessory air tank. Below 70 psi the pressure protection
valve closes, cutting off supply to the air springs. Note that the needles on the air pressure gauge show
the state of the primary and secondary air systems only; the accessory tank pressure may be low without
indicating this condition on the air pressure gauge. Always check the accessory tank for adequate
pressure if there is a low air pressure problem which is not indicated by the air pressure gauge.
Problem
Possible Cause
Remedies
Air spring failed.
Continual or repeated overextension of
the air spring.
Visually inspect for broken or loose
shock absorber or shock absorber
mounting bracket. Reconnect loose
parts and replace any defective parts.
Check the adjustment of the height
control valves.
Air spring(s) worn out.
Replace.
Air spring(s) fail to fully
deflate when all weight is re-
moved from
the suspension.
Restricted air line(s) between the height
control valve and the air spring(s).
Disconnect the height control valve
linkage and rotate the actuating lever
to the 45° down position. If the air
spring(s) remain inflated, check for
pinched or blocked line(s).
Shock absorber failures.
Overextension.
Shock brackets in wrong location.
Improper shocks installed. Check for
oil leaking from shock. If worn out,
replace.
Vehicle unstable or handles
poorly
†
.
Loose frame bolts or attachments.
Tighten frame bolts and attaching
parts to proper specifications.
Cracked or loose frame crossmembers.
Repair or replace damaged frame
members and torque all nuts and bolts
to proper torque specifications.
Bad bushings
Replace worn bushing; retorque to
specifications. Refer to replacement
instructions.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...