Bosch Rexroth A4VG 40 Series Instruction Manual page 62

62/68 Troubleshooting
Table 13: Axial piston unit malfunction table
Malfunction
Pressure/flow fluctuations/
instabilities
Excessive temperature of hydraulic
fluid and housing
Bosch Rexroth AG, A4VG Series 40, RE 92004-01-B/05.2017
Possible cause
Insufficient air bleeding of the hydraulic system
Insufficient suction conditions, e.g. insufficient
dimensioning of the suction line, viscosity of
the hydraulic fluid too high, suction height too
high, suction pressure too low, contaminants
in the suction line, suction filter too small or
blocked, etc.
Oscillate pressure limitation and pressure
control valves of the axial piston unit (boost-
pressure relief valve, high-pressure relief
valve,pressure cut-off)
Unstable control signal
Malfunction in the control devices or the
controller
Excessive inlet temperature at the axial piston
unit
Wrong setting or malfunction in the pressure
relief and pressure control valves (e.g. high-
pressure relief valve, pressure cut-off, pressure
controller)
Flushing flow of the flushing valve too low
Axial piston unit worn
Remedy
Fill the axial piston unit, suction line for the
hydraulic pump and the reservoir
Completely air bleed the axial piston unit and
hydraulic system
Check correct installation position
Machine/system manufacturer: Check the
system, e.g. optimize inlet conditions, use
suitable hydraulic fluid
Fill the suction line with hydraulic fluid
Remove foreign particles from the suction line
Check the filter system and change the filter as
necessary
Air bleed the axial piston unit and hydraulic
system
Contact Bosch Rexroth Service
Contact machine/system manufacturer or
Bosch Rexroth Service
Contact Bosch Rexroth Service
Machine/system manufacturer: inspect system,
e.g. malfunction in the cooler, insufficient
hydraulic fluid in the reservoir
Optimize the adjustment of the pressure
limitation and pressure control valves of the
axial piston unit and the pressure limitation in
the hydraulic system
Contact Bosch Rexroth Service
Contact machine/system manufacturer
Contact Bosch Rexroth Service
Replace axial piston unit, contact Bosch Rexroth
Service