HYDRAULIC SYSTEM MLC165-1 SERVICE/MAINTENANCE MANUAL
2-30
Published 05-26-17, Control # 238-02
Servicing the Pumps
It is not necessary to drain the hydraulic tank when servicing
the hydraulic pumps. To service the pumps, move the
hydraulic tank shut-off handle (10) Figure 2-27 on page 2-28
to the closed position (10a).
Move the hydraulic tank supply shut-off handle to the open
position (12) after servicing the pumps and before starting
the engine.
Replacing a Pressure Transducer
Before replacing a pressure transducer perform the following
test steps and replace the transducer only if any of the test
steps fail:
1. Perform the Pressure Transducer Test (Pressure
Transducer Test on page 2-33).
2. Attach a hydraulic pressure gauge to the suspect
pressure transducer.
3. If the gauge reads pressure greater than 0 psi (0 bar),
bleed the corresponding system until the gauge reads 0
psi (0 bar).
4. Repeat the Pressure Transducer Test.
5. Verify the signal voltage at the transducer is 0.96 to
1.04Vdc referenced to ground at 0 psi (0 bar).
6. Start the engine and run it at idle.
7. If testing a pilot pressure, actuate the function for the
pressure being read.
8. Verify the gauge pressure and the pressure displayed at
the Pressure Transducer Test screen are within the
limits of Table 2-11
.
Table 2-11 Transducer/Gauge Pressure Agreement
To replace a pressure transducer:
1. Lower all loads to the ground.
2. Move all control handles to off and park all crane
functions.
3. Shut off the engine.
4. Place a suitable container under the faulty pressure
transducers to catch the draining oil.
5. Disconnect the electrical connector from the pressure
transducer.
6. Slowly loosen the pressure transducer only enough to
relieve pressure.
7. Remove the pressure transducer.
8. Install the new pressure transducer and connect the
electrical connector.
9. Bleed the pressure transducer circuit:
a. Connect a bleed line with a shut-off valve to the
coupler on the pressure transducer manifold and
place the end of the hose into a suitable container.
b. Open the shut-off valve.
c. With all control handles off, start and run engine at
low idle.
d. When clear oil flows from bleed lines (no air bubbles
in oil), close the shut-off valve.
e. Shut off the engine.
f. Remove the bleed line from coupler at the pressure
transducer.
10. Perform the Pressure Transducer Test (Pressure
Transducer Test on page 2-33).
CAUTION
Avoid Damage to Pumps
Open the hydraulic tank shut-off valve before starting the
engine. Failing to perform this step will result in damage to
the pumps from cavitation.
WARNING
High Pressure Oil Hazard
Do not attempt to remove a pressure transducer unless
following steps are performed. High pressure oil will
exhaust from pressure transducer ports.
WARNING
Crush Hazard
When actuating a hydraulic function to read a pilot
pressure with a gauge, the associated parts will move
when the function is actuated. Keep all personnel clear of
the parts that will move during the test.
Pressure Type Pressure
Pilot +/- 20psi (1.4 bar)
System +/- 50 psi (3.4 bar)
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