Lull 944E-42 Service Manual User Manual download pdf (Page 418)

100

101

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.

MU1870

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