Lull 944E-42 Service Manual Bedienungsanleitung PDF herunterladen (Seite 132)

Hydraulic System

8-16

944E-42

8.6 HYDRAULIC SYSTEM PUMP

8.6.1 Pump Description

Hydraulic system pressure begins at the pump. Various

factors are involved in creating the relatively high

pressure used in the hydraulic system. Pump rpm,

controlled via a transmission input shaft (and dependent

on engine rpm), the internal pump passageways and the

differential between pump inlet and outlet openings, all

contribute to pressure supplied.

For internal service instructions contact your local

authorized service distributor.

8.6.2 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. However, 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.

8.6.3 Pump Replacement

a. Pump Removal

1. Park the machine on a firm, level surface, level the

machine, fully retract the boom, raise the boom, place

the transmission control lever in (N) NEUTRAL,

engage the park brake and shut the engine OFF.

2. Place a Do Not Operate Tag on both the ignition key

switch and the steering wheel, stating that the

machine should not be operated.

3. Temporarily block up or support the raised boom.

4. Open the engine cover. Allow the system fluids to

cool.

5. Properly disconnect the batteries.

6. Drain the hydraulic reservoir. Refer to Section 8.5.1,

“Hydraulic Oil Reservoir Draining.”

7. Thoroughly clean the pump (1) and surrounding

area, including all hoses and fittings before

proceeding.

8. Label, disconnect and cap the hydraulic hoses

attached to the pump.

9. Remove the bolts, lockwashers and washers

securing the pump to the transmission. Remove the

o-ring located between the transmission and the

pump. Wipe up any hydraulic oil spillage.

10. Remove the hydraulic fittings from the pump to use

for later installation.

Note: Before removing any fittings from the pump, note

their orientation to ensure correct installation.

Note: DO NOT disassemble the operating pump. The

pump is pre-set from the manufacturer. Any adjustments

or repairs performed by anyone other than an authorized

dealer could void the warranty.

b. Pump Installation

1. Install the fittings on the pump in the same

orientation as noted during removal.

MU7460

MU7470

1 2 ... 127 128 129 130 131 132 133 134 135 136 137 ... 265 266

Kommentare zu diesen Handbüchern

Keine Kommentare

Lull 944E-42 Service Manual Bedienungsanleitung Seite 132

Kommentare zu diesen Handbüchern