HYDRAULIC SYSTEM
The hydraulic system is composed of two major
component groups--the hydrostatic drive and the
auxiliary hydraulic group. The hydraulic motors and
cylinders use the same hydraulic oil reservoir and
hydraulic oil supply. Solenoid valves, ow-control valves,
dividers and other components allow simultaneous
function and control of all hydraulic systems. A
30-gallon hydraulic tank with suction strainers, charge
pressure and return lters stores and cleans the
hydraulic uid. An oil cooler is mounted with the engine
radiator to complete the hydraulic system.
The hydrostatic drive group consists of an axial piston
hydrostatic pump coupled to the rear of the diesel
engine. A hydraulic motor drives the rear axle. The
auxiliary hydraulic group consists of a two-section
gear pump mounted on the rear of the drive pump. If
equipped with the AWD option, a second axial piston
drive pump is installed and connected to the front wheel
drive motors.
ALWAYS use an equivalent grade of
hydraulic uid. Using hydraulic uids that do not
have equal characteristics can result in substandard
performance or possible failure of the hydrostatic
system. Contact your authorized LeeBoy dealer if
you need assistance.
Always wear eye protection when
inspecting for leaks in the hydraulic system. Never
use your hands to locate leaks as hydraulic uid
under pressure can pierce the skin and cause
serious injury and toxic reaction.
Never attempt makeshift repairs using
tape, clamps or cements in the hydraulic system.
The system operates under extremely high pressure
and such repairs could fail, causing serious injury.
Inspect the motor grader for hydraulic leaks daily.
Check that all ttings are secure and tight weekly. If
leaking uid is found, it is probably on the pressure
side of the hydraulic system. DO NOT OPERATE the
machine until the hydraulic leak is repaired.
Leaks on the suction side of the hydraulic system are
more difcult to nd and more serious since air or dirt
introduced into the system causes rapid component
wear and eventual failure. Some symptoms of suction
leakage are:
• Hydraulic uid “foaming.”
• Sluggish system operation.
• Unusual noises in the hydraulic pumps or motors.
Checking Hydraulic Oil Level
The hydraulic oil tank and sight gauge is located on the
right side of the machine. The hydraulic oil ll cap is
accessed on the right side of the grader just behind the
operator platform. (Figure 5-28)
NOTE: Wait 10 minutes after engine has been shut
down before checking hydraulic oil.
Oil level is determined by sight gauge.
Hydraulic oil should be added if the oil level falls
below the ll line. Never ll above the black ll line.
Hydraulic
Oil Cap
Sight
Gauge
Fill
Line
Figure 5-28. Hydraulic Sight Gauge and Filler Cap
Use extreme caution when removing
the ller cap to prevent foreign matter from entering
the hydraulic tank.
If hydraulic level is low:
1. Clean around the hydraulic oil ller cap before
removing to add hydraulic oil to the tank.
2. Fill tank to the black ll line on sight gauge.
3. Screw the hydraulic oil ller cap back onto the
hydraulic tank.
5
Maintenance
LeeBoy 685D Motor Grader 5-25
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