Oshkosh Corporation JLG 450AJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
5-34 – JLG Lift – 3121659
Platform Level Down Relief
The Platform Level Down relief is preset and does not normally
need checked or adjusted. If necessary, the following proce-
dure may be utilized for troubleshooting purposes:
1. With the tower boom fully lowered, lift the main boom
down until fully lowered.
2. Remove the hose from the Level Down port of the Level
Cylinder (V2 Port) - Install a pressure gauge capable of
reading pressures up to 3000 psi (207 Bar) onto this hose
and cap or plug the port in the Level Cylinder
3. Activate Platform Level Down function continuously.
4. Pressure that is observed should be 2000 ± 50 psi (138 ±
4 Bar). If necessary, loosen jam nut and adjust the Plat-
form Level Down Relief valve clockwise to increase and
counterclockwise to decrease.
5. Remove the gauge and reinstall the hose.
5.3 DRIVE PUMP PRE-FILL PROCEDURE
The case of the hydraulic drive pump, MUST be pre-filled
before starting the engine. Failure to do so can cause prema-
ture failure of the pump.
1. Fill the hydraulic reservoir.
2. Determine if the hydraulic oil tank sight level gauge is
higher than other hydraulic components.
a. Determine if the hydraulic oil tank sight level gauge
is higher than the hydraulic drive pump assembly.
b. Determine if the hydraulic oil tank sight level gauge
is higher than all hydraulic hose loops or routings
between the hydraulic tank and the drive pump
assembly.
c. If sight level gauge is the highest hydraulic oil level
point, proceed to step 3.
d. If sight level gauge is NOT the highest hydraulic oil
level point, low pressure air may need to be applied
to the hydraulic oil tank (fill cap via air regulator) in
conjunction with step 4 to get hydraulic oil to move
over the air locks created by these high spots.
3. If the machine is be equipped with a hydraulic oil cooler
option:
a. Determine if there is a hydraulic ‘tee’ fitting installed
at the hydraulic drive pump that has a ‘cap’ fitting
attached to it. (this will generally be at or near the
top of the hydraulic drive pump body). This ‘cap’ fit-
ting is to be used to manually fill the hydraulic drive
pump case.
b. Remove ‘cap’ fitting.
c. Fill hydraulic drive pump case with hydraulic oil.
d. Reattach and torque ‘cap’ fitting.
e. Prefilling of the hydraulic drive pump w/oil cooler
option is complete (Step #4 can be omitted at this
point.)
4. If machine is NOT equipped with a hydraulic oil cooler
option,
a. Locate a case access port on the hydraulic drive
pump. Preferably one located at or near the top or
upper sides of the pump.
b. Using the proper wrench, remove the O-ring plug to
allow air to escape from the hydraulic drive pump
case.
c. Hydraulic oil will flow by gravity from the hydraulic
tank to the drive pump.
d. When hydraulic oil starts to flow out this port, the
pump is full.
e. Re-install the O-ring plug and torque.
5. Pre-filling of the hydraulic drive pump is complete.