12 - 15
Checking Motor Leakage Rate
If the motor speed is low and the pump output is normal, the
cause could be excessive internal wear in the motor which
would result in high leakage of oil into the motor casing. By
measuring the amount of oil leaking from the motor casing
back to tank, it is possible to determine if the motor is worn.
The leakage test should be done on both left hand and right
hand motors so that their leak rates can be compared. If the
motors have similar test results it is likely that they are not
faulty (both are supplied with oil from the same source). If
both have test results outside the range quoted the fault is
probably somewhere other than in the motors.
Note: The following test must be done only with forward
selected. Due to the internal design of the motors, the
leakage rate is higher in reverse than in forward.
1 Stop the engine.
2 Remove the motor covers.
3 Connect a flowmeter into the motor drain hose A.
4 Disconnect and plug motor flushing line B. This is
important otherwise a true leakage rate cannot be
obtained.
5 Install a 0 - 400 bar (0 - 6000 lb/in
2
, 0 - 422 kg/cm
2
)
pressure gauge into the appropriate test point C on the
pump to measure the pressure generated in the motor
feed line.
6 Start the engine and, with the parking brake ON,
operate the motor forward service. Measure the amount
of oil expelled from the motor during one minute’s
operation and compare with the figures shown in the
table below.
Note: If the parking brake will not hold the machine
sufficiently to achieve the necessary line pressure, the
machine should be driven against a solid, immovable object
as shown at D.
If the flow rate is higher than normal, the motor should be
dismantled for repair as the distributor seals are probably
worn.
Average motor leakage rate
Section E Hydraulics
9803/8550
Section E
12 - 15
Issue 4
Pumps
S246250
A
423010
C
C
C
C
B
Pressure - bar (lb/in
2
)
20 (290) 50 (725) 100 (1450) 150 (2175) 200 (2900) 300 (4350) 400 (5800)
l/min (UK gal/min) 2.2 (0.48) 2.3 (0.50) 2.4 (0.53) 2.8 (0.62) 3.00 (0.66) 3.7 (0.81) 4.00 (0.88)
US gal/min 0.58 0.60 0.64 0.74 0.79 0.97 1.06
S203540
D
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