HYDRAULIC SYSTEM TMS800E SERVICE MANUAL
2-6
Published 01-29-2014, Control # 496-00
Removing Air From the Hydraulic System
Air entering the hydraulic oil will normally be removed
automatically by passage of the hydraulic oil over the baffles
in the hydraulic reservoir. If a component has been replaced,
the reservoir level is too low, or a leak develops in the suction
lines to the pumps, air can enter the system. If air becomes
entrapped in the hydraulic oil, it may be detectable in pumps
and motor operated components such as the swing
mechanism and hoist(s), because it can cause these units to
become noisy during operation. If noisy operation occurs,
first check the level of the hydraulic reservoir and replenish
as necessary. Then inspect for leaks in the suction lines
leading to the pumps.
Small leaks may be hard to locate. If a leak is not readily
detectable, use the following way to check for it:
• Seal all normal openings in the hydraulic system and the
reservoir. Using a positive means to control the pressure
(like a regulator), pressurize the hydraulic system to
0.14 to 0.28 bar (2 to 4 psi) and inspect all joints and
fittings for evidence of leaks. A soap solution applied to
the fittings and joints may also prove helpful in detecting
minute leaks while the system is pressurized. Remove
the pressure, repair any leaks found, and reopen any
openings (such as a vent) closed for inspection. Refill
the reservoir after completing any repairs or service.
Operate all hydraulic circuits several times in both
directions.
• This action should return any entrapped air to the
reservoir where it can be removed from the hydraulic oil
by the baffles.
• To remove entrapped air from telescope cylinders, lower
the boom to below horizontal and fully telescope the
boom in and out several times.
• If the air is not readily removed, lower the boom to below
horizontal, extend the telescope cylinders as far as
practicable, and allow the boom to remain in this position
overnight. This should allow entrapped air to find its way
to the holding valve so that telescoping the boom IN the
next morning should force the air back to the reservoir.
Ensure the boom is first telescoped IN (not OUT) in the
morning. Telescoping OUT may cause air to be forced
back into a cylinder.
• Entrapped air may be removed from cylinders having
wet rods by cycling. On certain cylinders, a plugged port
is provided on the rod end to bleed off entrapped air.
• In the event that air entrapment should persist, bleeding
of air by loosening various clamp and screw type fittings
may become necessary.
• If the above procedures fail to eliminate air entrapment,
contact your authorized Grove Distributor.
Parts Replacement
Parts found damaged or out of tolerance when maintenance
is being performed should be replaced. Refer to the Grove
Parts Catalog for proper replacement parts.
Directional Control Valves
The control valves that control the crane functions are
installed on the right side of the turntable.
Inspection
Inspect the control valves for visible damage, binding spools,
and evidence of leakage. If excessive internal leakage is
suspected during operation with a spool in its center position,
it is possible that the area between the spool and working
section bore of the valve body is worn beyond serviceable
limits. If this condition exists, the spool and body must be
replaced as an assembly.
Valve Leakage
Dripping hydraulic oil indicates some type of external
leakage. The machine should be removed from service for
immediate repairs. External leaks sometimes develop at
fittings and seals. Spool seals are susceptible since they are
subject to wear. Seals may be damaged by temperatures
that are too high, or by dirt or paint accumulation on the
spool. Damaged seals must be replaced.
A component functioning at reduced efficiency may indicate
that the control valve for that component is leaking internally.
If preliminary check-out reveals that adequate volume is
being supplied to the affected valve bank, relief valves are
WARNING
Locate the machine on a firm supporting surface and
position the boom over the front on outriggers when
extending the boom at low angles.
WARNING
Extreme care must be used when removing any plugs or
restrictions from a hydraulic system suspected to have
entrapped air that may be pressurized.
WARNING
Do not attempt to loosen fittings in pressurized lines or
while the hydraulic pumps are in operation.
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