80/88
Hägglunds DUc Drive unit
| Troubleshooting
Bosch Rexroth AB, Version 06.2020, RE 15326-WA
Causes Of Trouble And Its Effect In The Hydraulic Installation
Source of trouble,
effects
Mechanical Drive
Suction Line
Pump
Pressure Line
Return Line
Excessive noises
1. Coupling
wrongly aligned
2. Coupling loose
3. Coupling
defective
4. Loose mounting
on pump and/or
motor 5. Other
transmission
elements loose.
(V- belts, Toothed
belts(etc)
6. Pump or motor
defective
7. Direction of
rotation wrong
8. Noise
dampening not
incorporated in
design (rubber-
metal mountings)
Suction line
resistance
excessive because:
1. Suction valve
is closed or only
partially open
2. Suction filter
clogged or too
small (if fitted)
3. Suction line
blocked or leaking
4. Suction line has
wrong dimensions
(ie pipe bore ), or
too many bends.
5. Fluid level too
low
1. Pump is running
too fast
2. Maximum pump
pressure exceeded
3. Boost pump
defective
4. Shaft seals, or
seals on suction
side are defective
5. Pump defective
6. Pressure and
return lines
connected wrongly
7. Control system
oscillating
8. Noise
dampening not
incorporated in
design
1. Line mounts
missing or loose
2. Poor installation
3. Pipe bore too
small
4. Installation not
bled completely
1. Line mounts
missing or loose.
2. Poor installation
3. Pipe bore too
small
4. Installation not
bled
5. Return
terminates above
fluid level
6. Return filter
blocked
Insufficient power
and torque at the
hydraulic motor
(pressure too low)
1. Power
transmission
defective
2. V-belt or
Toothed belt
slipping
3. Direction of
rotation wrong
4. Motor defective
5. Key sheared at
pump or motor
1. Internal
leakages due to
wear
2. Unsuitable type
3. Pump defective
4. End-of-control
pressure set too
low, or control
element defective
1. Leakages
2. Excessive line
resistance
3. Pressure filter
blocked
1. Excessive line
resistance
2. Filter blocked
Jerky motor
movements.
(variations in
pressure and/or
flow)
1. Coupling
wrongly aligned
2. Coupling loose.
3. Coupling
defective
4. Loose mounting
on pump and/or
motor
5.Other
transmission
elements loose
6. Pump or motor
defective
7. Direction of
rotation wrong
Suction resistance
is excessive :-
1. Valve in the
suction line is
partially open
2. Suction filter
clogged or too
small (if fitted)
3. Suction line
blocked or leaking
4. Suction line is
sized wrong
5. Fluid level too
low
1. With variable
pumps, the control
system is defective
2. Pump defective
3. System
conditions react on
the pump control
system
4. Unsuitable pilot
valve
1. Installation not
bled completely
1. Excessive line
resistance
2. Filter blocked.
Foaming of the
hydraulic fluid
1. Suction line
leaks
2. Fluid level too
low
3. Wrongly
designed reservoir.
1. Shaft seals on
the suction side
are defective.
2. Case drain line
terminates above
the fluid level.
1. Return line
terminates above
the fluid level.
2. Vortex effect
due to wrongly
positioned lines
13 Troubleshooting
