SkyTrak 6036 Service Manual - Manual (Page 284)

Hydraulic System
8.68 Model 6036 Legacy
8.12 VALVES AND MANIFOLDS
Valves are devices that open or close passageways.
Manifolds contain circuit passageways involved in the
distribution of hydraulic fluid flowing under pressure.
There are various valves and manifolds in use on this
vehicle. As valves open and close, hydraulic fluid is
directed to flow through various passageways to the
prescribed circuit, causing vehicle functions to occur.
8.12.1 Unloader Valve
The unloader valve (Fig. 8-34, 1) creates system pressure
and distributes the hydraulic fluid for various vehicle
functions via its load sense, bypass to tank (via the oil
cooler), and primary and secondary valve ports. The
unloader valve is secured to the frame toward the front of
the vehicle near the main control valve (2).
Figure 8-34 The Unloader Valve
DO NOT loosen, disassemble or attempt to adjust any
cartridges unless specifically instructed by JLG to do so!
Tampering with the cartridges will irrevocably alter pres-
sure in the affected circuits.
a. Unloader Valve Removal
1. Park the vehicle on a firm, level surface, fully retract
the boom, raise the boom, place the travel select lever
in (N) NEUTRAL, place the neutral lock lever in the
(N) NEUTRAL LOCK position, engage the park brake
switch and shut the engine OFF.
2. Place an Accident Prevention Tag on both the
ignition key switch and the steering wheel, stating
that the vehicle should not be operated. Refer to
Section 1.5, “Accident Prevention Tag Usage.”
3. Temporarily block up or support the raised boom.
4. Unlock and open the rear door. Allow the hydraulic
fluid to cool.
5. At the unloader valve (Fig. 8-35, 1), label, disconnect
and cap the hydraulic lines (2). Remove the 12 hex-
head capscrews (3 and 11), 12 lockwashers (4), six
flange halves (5) and three o-rings (6).
Note: The check valve manifold (Fig. 8-35, 10) is secured
to the unloader valve by the hex-head capscrews (11)
attaching the hose and flange halves.
6. Remove the check valve manifold (Fig. 8-35, 10)
from the unloader valve (1).
7. Remove the three hex-head capscrews (Fig. 8-35, 7),
three lockwashers (8) and three washers (9) securing
the unloader valve (1) to the vehicle frame. Remove the
valve (1) from the vehicle. Wipe up any hydraulic fluid
spillage.
MA8390
1
Front
2
WARNING:
DO NOT get under a raised
boom unless the boom is blocked up. Always
block the boom before doing any servicing that
requires the boom to be up. Unexpected lowering
of the boom may cause death or serious injury.
WARNING:
Hot hydraulic fluid can
cause severe burns. Wait for hydraulic fluid to
cool before servicing any hydraulic component.
WARNING:
Escaping hydraulic fluid
under pressure can penetrate the skin, causing
death or serious injury. Relieve hydraulic pressure
before servicing any hydraulic component.