Lull 944E-42 Service Manual Download

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Hydraulic System

8.6

Model 644E-42/944E-42

Rev. 6/04

8.2

SAFETY INFORMATION

Petroleum-based hydraulic fluids are used in this vehicle.
The temperature of hydraulic fluid increases during the
operation of various hydraulic functions. A heated
petroleum-based hydraulic fluid presents a fire hazard,
especially when an ignition source is present. Hydraulic
fluid has a flash point that ranges from 300-600° F
(150-318° C) and an auto-ignition temperature of
500-750° F (262-402° C).

Accordingly, periodically inspect all hydraulic system
components, hoses, tubes, lines, fittings, etc. Carefully
examine any deterioration and determine whether any
further use of the component would constitute a hazard.
If in doubt, replace the component.

Note: Residual pressure may remain in hydraulic
cylinders, hoses, valve bodies, components, etc. If the
hydraulic lines going to or coming from a component are
taut, slowly and cautiously relieve (“bleed off”) pressure.

To relieve hydraulic pressure:

Whenever you disconnect a hydraulic line, coupler,
fitting, or other component, slowly and cautiously loosen
the part involved. A hissing sound or slow seepage of
hydraulic fluid may occur in most cases. After the hissing
sound has ceased, continue removing the part. Any
escaping oil should be directed into an appropriate
container. Cap or otherwise block off the part to prevent
further fluid seepage.

To relieve the hydraulic pressure on the snap to lock
connectors, the pressure must be relieved by slowly
loosening the bleed plug inline with the circuit being
disconnected. Refer to Section 8.5.3, “Snap Lock Fittings
& Special Tools,” for bleeding procedure.

Hydraulic system maintenance will, at times, require that
the engine be operated. Always follow safety
precautions.

A major cause of hydraulic component failure is
contamination. Keeping the hydraulic fluid as clean as
possible will help avoid downtime and repairs. Sand, grit
and other contaminants can damage the finely machined
surfaces within hydraulic components. If operating in an
exceptionally dirty environment, change filters and
inspect the fluid more often. When servicing the system,
cap or plug hydraulic fittings, hoses and tube assemblies.
Plug all cylinder ports, valves, and the hydraulic reservoir
and pump openings until installation occurs. Protect
threads from contamination and damage.

Hydraulic functions are actuated by interfacing with
electrical system components (switches, solenoids and
sensors). When the hydraulic system is not functioning
properly, check the electrical aspect of the malfunctioning
circuit also. Refer to Section 9.8, “Electrical System
Troubleshooting,” in this manual.

WARNING:

DO NOT service the vehicle

without following all safety precautions as
outlined in the “Safety Practices” section of this
manual. Failure to follow the safety practices
may result in death or serious injury.

WARNING:

Wait for hydraulic fluid to

cool before servicing any hydraulic component.
Hot hydraulic fluid can cause severe burns.

WARNING:

Relieve hydraulic pressure

before servicing any hydraulic component.
Escaping hydraulic fluid under pressure can
penetrate the skin causing death or serious
injury.

WARNING:

Before starting the engine,

verify that all hydraulic connections are
properly tightened. Escaping hydraulic fluid
under pressure can penetrate the skin causing
death or serious injury.

Lull 944E-42, Service Manual

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