Manitowoc Published 10-09-2020, Control # 259-06 2-13
MLC80A-1/MLC90A-1/MLC100A-1/MLC100-1 SERVICE/MAINTENANCE MANUAL HYDRAULIC SYSTEM
Inspecting the Hydraulic System
See Figure 2-12, page 15 for referenced item numbers.
The damaging effects of dirt, heat, air, and water in the
hydraulic system can only be prevented by regular, thorough
inspection of the system.
The frequency of inspection depends on operating
conditions and experience with the system. However, the
more often the system is inspected and deficiencies
corrected, the less likely the system will malfunction.
A good inspection program will include the following
procedures:
• Keep accurate records so future maintenance needs
can be projected.
• Check the hydraulic oil level daily prior to startup when
the oil is cold. The oil level should be at the full cold mark
on the decal next to the sight gauge (2).
• Fill the tank through the fill plug opening (12). Always
filter the oil through an owner-supplied 10-micron filter.
• Only use approved hydraulic oil in the system (see
Section 9).
• Replace the breather (5) when indicated (see Replacing
Breather on page 2-15).
• Replace the hydraulic filter elements (7) when indicated
(see Replacing Hydraulic Filters on page 2-16
).
• Clean the exterior of the system often. Do not let dirt
accumulate on or around any part of the system.
• Check for external leaks. Leaks not only are unsafe but
also attract dirt and sometimes allow air and water into
the system. Do not return leakage oil back to the
hydraulic tank.
Never check for hydraulic leaks with your hands. Check
for leaks with a piece of cardboard or wood.
• Look for oil leaks at fittings and between parts that are
bolted together. Tighten loose fittings and attaching
bolts to the proper torque and do not over-tighten.
If leakage persists at these points, replace the seals or
gaskets.
• Look for oil leaking from pump and motor shaft ends,
from valve spool ends, and from cylinder shaft ends.
Replace the seal if leakage is found at any of these
points.
• Replace tubes that are cracked, kinked, or bent.
• Replace hoses that are cracked, split, or abraded.
• Listen to the pumps and motors for unusual noises. A
high-pitched whine or scream can indicate that air is
being drawn into the pump or motor.
An air leak can be pinpointed by flooding the inlet fitting,
hose, or tube with oil. If there is an air leak, the oil will
cause a noticeable reduction in noise.
Correct the cause of any air leak, or the pump or motor
will be ruined.
NOTE: A high-pitched whine or scream from a pump can
also indicate cavitation (pump being starved of oil).
This condition may be caused by one or more of
the following:
• The shut-off valve (10) is closed. Open
immediately.
• There is a collapsed or plugged suction line
(inspect suction screen inside tank).
• The wrong oil (viscosity too high) is used.
• Look for signs of overheating such as heat-peeled parts,
burned and scorched oil odor, and darkening and
thickening of oil.
NOTE: If the oil temperature in the tank rises
above 85°C (185°F), the fault alarm
comes on and the Hydraulic Fluid
Temperature icon appears in the Fault
Bar of the main display.
• Have the hydraulic oil analyzed at regular intervals to
determine the condition of the oil and the extent of
system contamination. By having the oil analyzed on a
regular basis, an oil change interval meeting your
operating conditions can be established.
Contact your oil supplier for the availability of oil analysis
services and the steps that should be taken to obtain
these services.
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