JLG 800A_AJ Service Manual - Manual (Page 319)

SECTION 5 - HYDRAULICS
3120858 – JLG Lift – 5-37
4 WHEEL STEER (IF EQUIPPED)
1. At the platform console using the steer select switch
activate “2 wheel steer”.
2. Install a pressure gauge in port "G" on the control
valve.
3. With the aid of an assistant, activate steer left and
right, adjust front steer relief valve to 2500 PSI
(172.4 Bar). This pressure only affects the front axle.
4. At the platform console using the steer select switch
activate “crab” or “coordinated” steer.
5. At the main control valve block disconnect the wire
din connectors on the front steer valve. When steer
is activated only the rear steer will work.
6. Install a pressure gauge in port "G" on the control
valve.
7. With the aid of an assistant, activate steer left and
right, adjust rear steer relief valve to 2500 PSI (172.4
Bar) Reading at the valve bank. 2500PSI (172.4 Bar)
will give you 2000 PSI (137.9 Bar) at the cylinders.
8. Re-connect the front steer din connectors at the
valve bank.
5.10 HYDRAULIC OIL CHANGE-OUT
PROCEDURE
This procedure is written to change out JLG std. hydraulic
oil (Mobile 424) to cold weather fluid for machines operat-
ing in temperatures exceeding -20F. (-29C.). JLG recom-
mends (Mobile DTE 13). This procedure also applies to
change-out of cold weather oil to std. Mobil 424 hydraulic
oil.
NOTE: This is not a procedure for changing from a petro-
leum based fluid to a water based fluid. Stricter
guidelines are required when fluids are not compat-
able.
1. All booms stowed, (jib also), drain the hydraulic oil
tank, (approx. 40 gallons [150 L]).
2. Disconnect the main drive lines (A& B) from the right
rear drive motor, and right front motor if 4 wheel
drive. Drain into a container.
3. Disconnect the case drain lines from each of these
motors and drain. This will drain most of the drive
system. After they have been drained, reconnect
them.
4. Refill the hydraulic oil tank with the appropriate fluid
as recommended.
5. Remove the o-ring plug, (#10 size) on top of the
Rexroth load sense pump. The plug is removed until
the oil flows out of the pump. This insures that the
pump cases are full of oil before starting. Install the
plug after there is a steady flow of oil.
6. Jog the Auxiliary power pump 2-3 times (not ener-
gizing a function, only the Aux. Pump switch). Then
activate the Aux. switch for approx. 20 seconds. This
will flush the Aux. system.
7. Start the engine and let idle for a couple of minutes.
Shut off engine.
8. If the machine has a jib: Remove the hose con-
nected to port #17 on the main valve block and
drain into a container that will hold at least 2 gallons
(8 L) of oil. Plug port #17. Start the engine and acti-
vate jib up to the end of stroke. Stop, reconnect the
hose to port#17, and cycle the jib function.
9. Remove the hose at port #8 on the main valve
block. Place this hose inside a container that will
hold approx 10 gallons (38 L). Activate tower lift up
to the end of stroke. Reconnect the hose on port #8
and lower the tower boom.
NOTE: Depending on the ceiling height, the upper boom
might have to be lowered while lifting the tower.
10. Locate the manual pull valve on the side of the oil
tank (red knob). Disconnect the 1/4" hose (port #1)
where it connects to the side of the hyd. return filter
(plug the port) and place into a container that will
hold approx. 10 gallons (38 L). Start the engine. Pull
the red knob and hold it open, while tower is lifting
up. Raise the tower 7-8 ft. (2-2.5 m) and stop.
Release the red knob, and lower the tower boom. At
the end of stroke, hold the switch in the down posi-
tion. You will hear a hissing sound coming from the
upright. this is oil being replenished in the tower cir-
cuit. Hold the switch until the sound stops. (approx.
15-20 secs.) Repeat this procedure 2 more times.
Reconnect port #1 hose to the hyd. return filter.