Lull 944E-42 Service Manual - Manual (Page 418)

Hydraulic System
8.166 Model 644E-42/944E-42 Rev. 6/04
8.11.1 Pump Failure Analysis
The pump is the “heart” of the hydraulic system, and
whenever there is a problem in the system, the pump
often is blamed. Yet, pump failure is seldom due to failure
of pump components. Pump failure usually indicates
another problem in the hydraulic system.
According to pump manufacturer statistics, 90-95 percent
of pump failures are due to one or more of the following
causes:
• Aeration
• Cavitation
• Contamination
• Excessive Heat
• Over-Pressurization
• Improper Fluid
In the event of pump failure, investigate further to
determine the cause of the problem.
8.11.2 Pump Replacement
a. Pump Removal
1. Park the vehicle on a firm, level surface, fully retract
all hydraulic cylinders, ground the attachment
(if any), place the travel select lever in the [N]
NEUTRAL DETENT position, engage the park brake
switch and shut the engine OFF.
2. Place an Accident Prevention Tag on both the
ignition switch and the steering wheel, stating that
the vehicle should not be operated. Refer to Section
1.5, “Accident Prevention Tag Usage.”
3. Unlatch and open the engine cover. Allow the
hydraulic fluid to cool.
4. Remove the four capscrews (1) securing the inlet
flange halves (2) to the pump (3). Remove the inlet
tube (4) and o-ring (5).
5. Remove the four capscrews (6) securing the front
outlet flange halves (7) to the pump (3). Remove the
front outlet hose (8) and o-ring (9). Cap the outlet
hose to prevent unnecessary fluid spillage.
6. Remove the four capscrews (10) securing the rear
outlet flange halves (11) to the pump (3). Remove
the rear outlet hose (12) and o-ring (13). Cap the
outlet hose to prevent unnecessary fluid spillage.
7. Remove the four capscrews (14) and plain washers
(15) securing the pump (3) to the transmission.
Remove the pump and o-ring from the vehicle. Wipe
up any hydraulic oil spillage.
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.
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