TABLE OF CONTENTS

Chapter 9: Troubleshooting
Front Axle and Reduction Differential .......................................................................................... 9.1
Brake System ............................................................................................................................... 9.2
Steering System........................................................................................................................... 9.4
Hydraulic System ......................................................................................................................... 9.6
Rear Axle ..................................................................................................................................... 9.8
Mast and Forks ............................................................................................................................ 9.9
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 TROUBLESHOOTING

Troubleshooting
Front Axle and Reduction Differential
Complaint Possible Cause Remedy

Gear noise comes out Teeth worn excessively or tooth contact out Readjust or replace
continuously during of adjustment in spiral bevel drive
normal cruising run
Bearing preloads too much or too little, Readjust or replace
or bearings are worn excessively
Hub bearings broken Replace
Improper tooth contact between Readjust
reduction pinion (on output shaft) and
reduction gear
Irregular noise comes Bearings associated with spiral bevel Replace
out during normal travel drive or hub bearings broken
Differential side gears have broken teeth, Replace gears or washer
or thrust washers worn
Metal piece in axle housing Clean and replace oil
Bolts securing axle shaft or differential carrier Retighten
are loose
Abnormal noise comes Fit differential gears in differential case Replace worn parts
out when turning a are out of specification due to wear
corner
Broken teeth on differential pinions or Replace defective parts
side gears, or pinions seized on spiders
Differential overheats Bearings broken due to too large a Replace bearing and readjust
preload preload
Backlash between reduction pinion Replace bearings and readjust
(on output shaft) and reduction gear preload and backlash
too small

99759-8B110
9.1
TROUBLESHOOTING

Brake System
Complaint Possible Cause Remedy

Lack of Oil leaking past primary cup in master Replace piston cup if cylinder is worn.
braking force cylinder Replace cup and fluid if the cup is
distorted.
Oil leaking past cups in wheel cylinders Replace pipe and connector and
retighten
Oil leaking from oil pipe connection Retighten
Shoe linings excessively worn Replace
Linings dirty with oil or grease Clean or replace
Pedal stroke is Air trapped in brake oil line Bleed air at master cylinder and
too large wheel cylinder
Piston cup defective in master cylinder Replace
Not enough fluid in reservoir Refill
Push rod-to-piston clearance too large Readjust
in master cylinder
Service Brakes

Brake fluid leakage Replace piston cup if cylinder is worn.

Replace the cup and fluid if the cup is
distorted.
Automatic adjusting device out of order Check cable guide and adjusting
spring installation. If they are defective,
replace fitting cable, lever and
adjusting screw.
Uneven braking Lining or drum dirty with oil or grease in less Clean or replace
(machine pulls to effective brake
one side)
Wobbly or loose-mounted drum in less Replace drum. Readjust and retighten.
effective brake
Brake squeals Linings glazed Replace shoe & lining assembly
Linings badly worn Replace
Backing-plate securing bolts loose Retighten
Wheel bearings loose Readjust preload and retighten
Brake drum dirty Clean
Brake chatters Anchored ends of shoes rattling on anchor Repair or replace
or clatters
Shoe ledges badly worn Replace backing plate
Piston badly worn in wheel cylinder Replace

99759-8B110
9.2
 TROUBLESHOOTING

Complaint Possible Cause Remedy

Lever stroke is Lining-to-drum clearance too small Readjust

too small
Squeals during Lining-to-drum clearance too small Readjust
traveling
Brake drum badly distorted Repair or replace
Parking Brake

Will not apply Parking brake cable longer than specified Check drum-to-lining clearance and,
if brake will not apply, turn adjusting
knob clockwise
Linings worn to service limit Replace shoe & lining assembly
Lining-to-drum clearance too small Readjust
Lack of brake lever operating effort Readjust to
25 to 30 kgf (55 to 66 lbf) [245 to 294 N]

Complaint Possible Cause Remedy

Hard steering a) Overloaded steer axle Reduce load

b) Damaged mechanical linkage Replace
c) Dry mechanical linkage joints Lubricate
d) Mechanical joints too tight Readjust
e) Kingpin bearings improperly preloaded Readjust
f) Low pump pressure Replace pump
Truck wanders a) Damaged or worn mechanical linkage Replace
Steering System

b) Loose cylinder piston Replace cylinder rod

Truck drifts a) Damaged or worn mechanical linkage Replace
b) Tire diameter differs between right and left Replace tire
Erratic steering Loose cylinder piston Replace cylinder rod
Excessive free play Damaged or worn linkage between cylinder Replace
at steered wheels and steered wheels
Axle shimmy a) Excessive clearance between the kingpin Repair or replace
and its bearings
b) Worn or damaged hub bearing Replace
Rear tires wear Tire on one side differs in kind or brand Replace tires
prematurely from that on the other side.
or unevenly

99759-8B110
9.3
TROUBLESHOOTING

Steering System
Complaint Possible Cause Remedy

Slow steering, Worn or malfunctioning pump Replace

hard steering or
loss of steering Malfunctioning relief valve Readjust or replace
Worn or malfunctioning steer gear Replace
Pipe or tube flattened, or restriction in an oil line Clean or replace
Truck wanders Air in system Low level of oil Fill as required
Leaking joint Tighten joint
Pinched pipe or hose Straighten or replace
Worn steer gear Replace
Steering slip Worn steer gear Replace
Leakage of cylinder seals or at lines between steer gear Repair
and cylinder
Temporary hang-up in Thermal shock—caused by actuation of hydraulic lift and Correct operating
steering tilt for long periods of time without actuation of steering procedure
system, creating more than a 28°C (50° F) temperature
differential between the oil in the tank and the oil in the
steer gear.
Erratic steering Air in system Low level of oil Fill as required
Leaking joint Tighten joint
Pinched pipe or hose Straighten or replace
Thermal shock damage to steer gear Replace
Motor not operating at correct speed Repair/replace
Spongy or soft steering Air in system Low level of oil Fill as required
Leaking joint Tighten joint
Pinched pipe or hose Straighten or replace
Air trapped in cylinder Bleed air

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9.4
 TROUBLESHOOTING

Complaint Possible Cause Remedy

Steering wheel turns Problem with Column loose or damaged Repair or replace
with no axle response steering column
Column splines damaged or Repair or replace
disengaged from steer gear
Air in steer gear Starved at startup Temporary
Starved from long period of non-use Temporary
No flow to steer gear Low oil level Fill as required
Ruptured hose Replace
Thermal shock damage to steer gear Replace
Blown piston seal Replace
Steering instability or Air in lines Pump sucking air at inlet Check joints
oscillation
Components or lines contain air Bleed circuit
Improper relief setting Readjust
Steering wheel turns in Lines connected to wrong cylinder ports Correct connections
wrong direction
Excessive freeplay At steering wheel Loose steering wheel nut Tighten
Damaged or worn column shaft Replace
At steered wheels Leaky cylinder seals Replace
Binding or poor Binding or misalignment between column and steer gear Readjust steer gear
centering of steering mounting bracket or
wheel replace rubber mounting
grommets
High back pressure in tank return line Clear blockages
Contamination in steer gear unit Clean unit
Steer gear locks up Contamination in steer gear unit Clean unit
Insufficient hydraulic power Check pump and power
supply
Worn or damaged steer gear or steer gear pin Replace

99759-8B110
9.5
TROUBLESHOOTING

Hydraulic System
Complaint Possible Cause Remedy

Will not lift or tilt Not enough oil in hydraulic tank Refill
Relief valve out of order because of:
1) Seized main valve Replace
2) Broken valve spring Replace relief valve
Oil pump defective Replace
Control valve switch misaligned or defective Readjust or replace
Will not lift rated Relief valve out or order because of:
load 1) Too low a relief valve setting Readjust
2) Defective plunger and poppet seat Replace relief valve
3) Weakened spring Replace relief valve
4) Damaged O-ring in valve case Replace O-ring
Oil pump defective Replace
Piston seals worn or damaged Replace
Lift speed is too low Rpm too low Adjust
Control lever installed loose, resulting in not Repair or replace
enough spool stroke
Lift and Tilt Cylinders

Tank strainer clogged Clean or replace

Pump not delivering enough oil Repair or replace
Lowering speed Sleeve seized in flow regulator valve Repair
is too low
Dirt in flow regulator valve Clean, repair system and replace
defective hose
Abnormal resistance to flow due to flattened Replace hose
hose or local clogging
Cylinder vibrates Piston rod distorted Repair or replace
when actuated Control lever installed loose, resulting in not Repair or replace
enough spool stroke
Air in oil circuit Bleed air by operation cylinder
through full stroke
Not enough oil in hydraulic tank Refill
Load will not hold Control valve spool leaking internally Replace
Lift connector on bottom of control valve Torque to 33 ± 3.5 ft•lbs
not tight
Sliding (inside) surface of cylinder tube Repair or replace cylinder assembly
slightly grooved
Sliding (inside) surface of tube badly grooved Replace
Piston seals broken or distorted Replace seal kit
Oil leakage from piping Repair or replace
99759-8B110
9.6
 TROUBLESHOOTING

Lift and Tilt Cylinders, continued Complaint Possible Cause Remedy

Mast tilts forward Control valve spool leaking internally Replace

(drifts)
Foreign particles lodged between packing Replace packing
and mating surface
Piston seal damaged Repair
Cylinder distorted Repair or replace
Bushing leaks Foreign particles lodged between sealing Replace
members such as oil seals and dust seals
Oil seals and dust seals defective Replace
O-rings damaged Replace
Cylinder distorted Repair or replace

Hydraulic tank heats Oil viscosity improper Change oil

excessively
Overload Check working conditions and, if
overloaded, urge the operator to
stay within the load limit
Local overheating of oil line due to a large Repair or replace
restriction flow
Hydraulic Tank

Relief valve adjustment improper Readjust pressure setting

Pressure drop due to weakened or broken Repair or replace and readjust
springs
Hydraulic pump worn Replace
Outlet pipe or tube flattened, or restriction Repair or replace
to flow
Cylinders move Shortage of oil due to a natural loss Refill
too slowly
Oil leakage due to damaged oil line seals Repair or replace
Oil viscosity too high Change oil
Cylinders move too Hydraulic pump defective Check pump and piping; repair or
slowly replace
Oil leakage from oil line Check oil for level and condition;
and/or change oil
Abnormal rise in oil temperature Check control valve spools for
Hydraulic Pump

misalignment: repair or replace

Hydraulic pump leaking internally Replace pump
Noisy Poor pumping Refill
Cavitation 1. Check suction pipe for any flat portion
or loose connection; retighten or
replace
2. Check shaft oil seal for airtightness;
replace pump
3. Check pump body for any outside
interference; repair
Forks will not lower Control Valve Solenoid Check positive and negative to solenoid.
Hyd. Cont.
Valve

Check wire #25 positive or wire #26 Repair wiring or replace solenoid.
negative to the solenoid.

99759-8B110
9.7
TROUBLESHOOTING

Rear Axle
Complaint Possible Cause Remedy

Hard steering Low pump pressure Check pressure, replace pump as needed
Damaged mechanical linkage Replace
Dry mechanical linkage joints Lubricate
Mechanical joints too tight Readjust
Kingpin bearings improperly preloaded Readjust
Truck wanders Damaged or worn mechanical linkage Replace
Loose cylinder piston Replace cylinder rod
Truck drifts Damaged or worn mechanical linkage Replace
Tire diameter differs between right and left Replace tire
Erratic steering Loose cylinder piston Replace cylinder rod
Excessive freeplay Damaged or worn linkage between cylinder Replace
at steered wheels and steered wheels
Axle shimmy Excessive clearance between the kingpin and Repair or replace
its bearings
Worn or damaged hub bearing Replace
Rear tires wear Tire on one side differs in kind or brand from Replace tires
prematurely or that on the other side
unevenly

99759-8B110
9.8
 TROUBLESHOOTING

Mast and Forks

Complaint Possible Cause

Lift bracket and inner mast Main rollers and side rollers have proper clearance
do not move smoothly
Rollers involved are binding on their shafts
Rollers damaged
Improper mast-to-strip clearance
Lift bracket or inner mast Too much clearance on side rollers, or side rollers are damaged
cocks
Lift chains unequally tensioned
Shim adjustments unequally made on left and right lift cylinders
(at maximum height)
Mast makes noise Rollers not rotating smoothly on their shafts or are damaged
Load drops (drifts) Lift cylinder packing damaged
Lift cylinder bore grooved
Control valve defective
Entire mast shakes Mast-support bushing worn
Mast is distorted Improper loading or overload
Fork tips differ in height Finger bar bent
Forks bent
Distortion of mast due to off-center loading

99759-8B110
9.9
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