Troubleshooting 51/56
RE 15215-01-B/11.2015, MCR Series 30, 31, 32, 33 and 41,
Bosch Rexroth AG
14.2 Malfunction table
Table 12: Radial piston motor malfunction table
Fault
Possible cause
Remedy
Unusual noise
Output speed too high, causing cavitation and/or
pistons to lift off cam.
Check motor speed versus machine specification.
If too high, reset pump, and/or engine speed.
Charge pressure too low, causing cavitation and/
or pistons to lift off cam.
Check charge pressure versus machine
specification. If necessary, adjust, repair or
replace charge pump (closed circuit) or other
source of charge pressure (open circuit).
High case pressure causing pistons to lift off
cam, or 2-speed spool (where fitted) to remain
partially shifted.
Check case pressure versus machine
specification. If too high, check drain line for
blockages.
Low 2-speed shift pressure causing partial
shifting of 2-speed spool (where fitted).
Check 2-speed shift pressure versus machine
specification. If too low, adjust, repair or replace
pressure source.
2-speed spool (where fitted) jammed in a partially
shifted position.
Check 2-speed spool and replace spool and/or
motor housing as necessary.
Motor mounting screws are loose, causing motor
to rattle against frame.
Check motor mounting screws are correctly
tightened per machine manufacturer’s
specifications.
Improper fixing of wheel or load to motor output
shaft.
Check wheel or load is attached per machine
manufacturer’s specifications, and is correctly
aligned.
Improper fixing of hydraulic lines causing rattling
against machine frame.
Check installation of lines per machine
manufacturer’s specifications.
Internal damage to radial piston motor.
Strip down and inspect motor. Replace defective
parts or complete motor as necessary.
Air intake.
Completely bleed hydraulic system. Check
tightness of all connections.
Brake release pressure too low, causing brake
(where fitted) not to be fully released.
Check brake release pressure versus machine
manufacturer’s specification and adjust, repair or
replace pressure source as necessary.
High pressure fluctuations
Internal damage to radial piston motor.
Strip down and inspect radial piston motor.
Replace defective parts or complete motor as
necessary.
Out-of-balance or fluctuating load.
Check load and attachment of load per machine
manufacturer’s specifications, and adjust as
necessary.
Blocked or incorrectly sized supply or return line. Check main lines to motor A and B ports for
blockages, and that they are correctly sized per
machine manufacturer’s specifications.
High speed fluctuations
Internal damage to motor, causing leakage
variation.
Blank off flushing (if fitted) and check motor case
drain leakage for pulsations, while rotating motor
at low speed, under load. If necessary, strip down
and inspect motor, paying particular attention to
piston rings. Replace defective parts or complete
motor as necessary.
Faulty pump or pump controller.
Check pump and pump controller versus machine
manufacturer’s specifications and adjust, repair
or replace as necessary.
Fluctuating signal from speed sensor (where
fitted and used in closed-loop speed control
system).
Check output from speed sensor on oscilloscope
(should give correct number of pulses per motor
revolution per specification). Replace sensor or
target disc as necessary.
