JLG Skytrak 6036 Service Manual page 128

positioned so that hydraulic flow is blocked at port
C, Fig. 9.6: no pressure is applied to the service
brakes. Return flow from the service brakes
passes through ports B to D to the reservoir.
When the brake pedal in the operator's cab is
depressed, the brake valve spool is positioned so
that flow is directed through ports C to A, Fig. 9.6,
to the service brake pistons. As pressure is ap-
plied, the pistons press the brake discs together
slowing or stopping the wheel. The brake pedal will
return to the up position when released.
Park Lock Release Valve
When the park lock switch on the instrument panel
is placed in the engaged (up) position, the park
lock release valve solenoid is de-energized and
the valve spool is spring positioned so that hydrau-
lic flow from the park lock piston is directed through
ports B to C in the park lock release valve, Fig. 9.6.
With no pressure on the park lock piston, the park
lock springs force the discs together, this engages
the park lock. With the park lock release valve
solenoid in the de-energized position, pressurized
hydraulic oil is blocked at port D. The park lock
light on the dash will illuminate whenever the park
lock is engaged and the ignition switch is in RUN
position.
When the park lock switch on the instrument panel
is placed in the disengaged (down) position, the
park lock release valve solenoid is energized and
the valve spool is positioned so that the hydraulic
flow is directed through ports D to A, in the park
lock release valve, Fig. 9.6, to the park lock. With
hydraulic pressure being applied to the park lock
piston, the park lock springs are compressed.
Which disengages the park lock discs.
IMPORTANT: Never engage the park lock while
the machine is in motion. The park lock is not
designed to be used as a means to slow or stop
machine travel and could be damaged as a result.
b. Pressure Checks and Adjustments
Sequence Valve
1. Engage the park lock, place the travel select
lever in neutral, and stop the engine.
Warning !
Relieve hydraulic pressure before servicing any
hydraulic component. Escaping hydraulic fluid
under pressure can penetrate the skin causing
serious injury.
9-15
Section 9. Hydraulic System
2. Operate the hydraulic controls after the engine
has stopped to relieve any trapped pressure.
Warning !
Wait for the hydraulic fluid to cool before servic-
ing any hydraulic component. Hot hydraulic fluid
can cause severe burns.
3. Remove the transmission cover from the
frame.
4. Install a tee and pressure gauge capable of
measuring 0-4000 psi (275,6 bar) in the 15
gpm section outlet of the tandem pump, Fig.
9.6.
Warning !
Before starting the engine be sure all hydraulic
connections are tight and all tools are removed
from the forklift.
5. Start the engine and allow it to run at idle.
6. Check the pressure gauge reading at the
tandem pump.
7. Pressure gauge reading should read 575 ± 25
psi (39,6 ± 1,7 bar). If not, adjust the se-
quence valve, turning the adjustment screw
clockwise to increase pressure or counter-
clockwise to decrease pressure.
8. Stop the engine. Operate the hydraulic
controls after the engine has stopped to
relieve any trapped pressure.
9. Remove the pressure gauge and tee from the
tandem pump and reconnect the hydraulic
line.
10. Install the transmission cover after adjustment.
Pressure Reducing Valve
1. Engage the park lock, place the travel select
lever in neutral, and stop the engine.
Warning !
Relieve hydraulic pressure before servicing any
hydraulic component. Escaping hydraulic fluid
under pressure can penetrate the skin causing
serious injury.
Model 6036 S/N 9B0499 and Before