19. Basic Servicing Practices
3-11
• The hydraulic system is hot during and immediately after
operation. It is also given high pressure during operation.
Therefore, check and service the hydraulic system care-
fully as follows:
• Put the bucket on the level ground so that no pressure
is applied to the hydraulic cylinder circuits.
• Be sure to stop the engine.
• Wait until the temperature drops sufficiently and then
start maintenance since the hydraulic oil and the lube
oil are at high temperature and high pressure immedi-
ately after operation.
Do not suddenly remove any plugs, screws or connecting parts of the hoses. Otherwise oil may
spout out due to residual internal pressure even when the oil temperature has lowered. Be careful
not to face them when loosening them to prevent injury, and loosen them little by little to remove the
internal pressure.
• Always relieve the internal pressure before checking and servicing the hydraulic system according
to the following procedure.
(1) Stop the engine.
(2) Turn the starter key to "ON" position.
(3) Push the lock lever forward to set it in unlock position.
(4) Alternatively press the right and left sides of the lever switch several times for the P.T.O. circuit
and move levers or pedals to full stroke ends several times for the other actuator circuits.
• Check the hydraulic oil level, replace the filter element, and replace the hydraulic oil when necessary.
• When removing the hydraulic hoses and pipings, check the O-ring and the packing for damage before
reinstalling them.
Replace them if they are damaged.
• Release air after replacing or cleaning the hydraulic oil filter element or strainer, repairing or replacing
the hydraulic equipment, or removing the hydraulic cylinder or piping.
Release air according to the following procedure:
1) Set the engine rotation to medium. That is, set the lever in the middle of the stroke.
2) Slowly operate each cylinder 4 to 5 times to approximately 3.9 in. (100 mm) before both stroke ends.
3) Operate the cylinder 4 to 5 times at full stroke.
• Failure to release air from the hydraulic cylinder and operating it suddenly to the stroke ends could
cause piston seal damage.
• If air is left in the hydraulic circuit, air is compressed and swollen by the load and the hydraulic equip-
ment does not operate smoothly.
Air in the hydraulic circuit may shorten the service life of the hydraulic pump.
4) Check the hydraulic oil level and replenish to the specified level if necessary.
19-3. Hydraulic system
Retract the bucket and arm cylinders to place
the bucket on the ground.
Upper limit
Lower limit
000521-00E
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