HYDROSTATIC TRANSMISSION TROUBLESHOOTING
10
Hydrostatic
transmission
components
Check points
& instruments
Transmission does not
operate in any
direction
Transmission operates
sluggishly or
jerkily
Engine
overloading
Low motor
output torque
Transmission operates
hot (motor case temp.
aboute 80°C/180°F)
Low motor
output speed
System is
noisy
Leakage from
shaft seal
Engine
Low engine power.
Engine damaged.
Overloaded engine.
The engine does not
run at max. speed.
The engine does
not run at max
speed.
Pump drive
coupling
Pump
Boost pump
Disaligned shaft. Check
distorsion in mounting,
axial interference, faulty
installation, excessive
overloading.
High pressure
relief valve faulty
or damaged (no
pressure at port Ga, Gb).
Boost pressure relief
valve damaged.
Setting of high pressure
relief valve is low.
(check pressure at
port Ga, Gb).
Setting of high
pressure relief valve
low (check pressure
at port Ga, Gb).
Excessive operation at
high pressure relief
valve setting.
Cavitation in the
pump group.
Mechanical fault
in pump.
Shaft seal damaged.
Excessive pump leakage
caused by internal
damage to pump.
Wrong direction
of rotation.
Boost pump
damaged.
Pump control
Check the entire control
mechanism from operator
consolle to pump lever.
The linkage might be faulty.
Control linkage
sticking.
Pump drain
piping
Return lines directly
connected to reservoir.
Unsuitable
drain hose.
Motor
Internal damage
to motor. Check
the drain flow.
Internal damage to
motor. Check
the drain flow.
Internal damage to
motor. Check
the drain flow.
Internal damage
to motor.
Check the drain flow.
Shaft seal damaged.
Unsuitable drain
hose.
Motor output
coupling
Motor coupling
damaged.
Unsuitable gear
ratio.
Reservoir
Low fluid level.
High oil
temperature.
Low fluid level
in reservoir.
Unsuitable oil.
Low fluid level in the
reservoir. The diffuser of
return lines in the reservoir
aren't submerged below
fluid level.
Suction piping
Disconnected or
demaged pump suction.
Air in the system.
Check for suction line
air leaks.
Suction filter
Suction filter
plugged.
Suction filter plugged.
Check pressure at
max speed.
Air in suction
line.
Heat exchanger
Heat exchanger by
pass valve faulty.
Heat exchanger dirty.
Internal damage to
pump. Insufficient
boost pressure or
boost flow.
Tacho-meter.
Ga, Gb ports 0 - 600
bar manometer.
Gs port 0 - 60 bar
manometer.
Oil level indicator.
Vacuum-meter.
Heat exchanger by pass
valve faulty.
Suction filter
plugged.
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