Removing Air From The Hydraulic System - Manitowoc Grove RT765E-2 Service And Maintenance Manual

HYDRAULIC SYSTEM
6. Connect the cylinder return line and lower the boom to
its stowed position. Replenish the reservoir hydraulic oil
level as required.
7. Disconnect the return line from an outrigger extension
cylinder and fully extend the outrigger.
8. Connect the outrigger return line and retract the
outrigger. Replenish the reservoir hydraulic oil level as
necessary.
9. Repeat Steps 7 and 8 for the remaining outriggers.
CAUTION
When draining the outrigger cylinders, always operate
either both front or both rear cylinders together to prevent
twisting the crane.
10. Disconnect the return lines from a pair of outrigger jack
cylinders and activate the cylinders to their maximum
down positions.
11. Connect the return lines and raise the outrigger jack
cylinders to the stowed position. Replenish the reservoir
hydraulic oil level as necessary.
12. Repeat Steps 10 and 11 for the remaining two outrigger
cylinders.
13. Disconnect the return line from the telescope cylinder
and fully extend the boom.
14. Connect the return line and retract the boom. Replenish
the reservoir hydraulic oil level as necessary.
15. Disconnect the return lines from both front steer
cylinders and turn the front wheels to the extreme right.
16. Connect the return lines and turn the front wheels to the
extreme left and then back to center. Replenish the
reservoir hydraulic oil level as necessary.
17. Repeat Steps 15 and 16 for the rear steering cylinders.
18. Raise the crane on outriggers.
19. Disconnect the line from port A of the axle lockout valve.
20. Using a jack under the rear wheel on one side of the
crane, jack up the wheel to maximum travel.
21. Connect the line to port A of the axle lockout valve and
disconnect the line from Port B.
22. Repeat step 19 using the other rear wheel.
23. Connect the line to port B of the axle lockout valve.
Energize the axle lockout valve. Replenish the reservoir
hydraulic oil level as necessary.
24. Disconnect the return line from the main hoist motor and
fully hoist up the hoist.
2-6
25. Connect the return line to the main hoist motor and fully
26. Repeat Steps 24 and 25 for the auxiliary hoist as
27. Disconnect one of the lines from the swing motor and
28. Connect the line to the swing motor, then drive the swing
When hydraulic oils are changed or added, ensure that
hydraulic oils of different manufacturers are of the same
specifications, however, discoloration (milkiness) may
occur. Mixing incompatible hydraulic oils may result in
improper operation or damage to the machine.
When hydraulic oils are changed, recheck the reservoir
hydraulic oil level after brief system operation and add
hydraulic oil as required. Working reservoir capacity
(capacity to full mark) is 150 U.S. gallons (568 liters). Ensure
the crane is level and in the travel mode of operation when
the hydraulic system is being filled. The system must be filled
with all cylinders retracted. Fill the reservoir to the full mark
on the reservoir sight gauge. After the reservoir is filled,
operate all circuits and recheck the reservoir sight gauge.
Add hydraulic oil as required.

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.
Minute leaks may be hard to locate. If a leak is not readily
detectable, use the following way to check for it:
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Published 9-04-2014, Control # 422-08
RT765E-2 SERVICE MANUAL
hoist down the hoist, then hoist up again. Replenish the
reservoir hydraulic oil level as necessary.
necessary.
drive the motor in the direction it will go.
motor in the opposite direction until the boom is centered
and forward. Replenish the reservoir hydraulic oil level
as necessary.
CAUTION
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 2 to
4 psi (13.8 to 27.6 kPa) 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