Lull 944E-42 Service Manual User Manual download pdf (Page 428)

100

101

Hydraulic System

8.176

Model 644E-42/944E-42 Rev. 6/04

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 Valve Plate Assembly

The main control valve (1), accumulators (2),

accumulator charge/secondary function valve (3),

auxiliary hydraulic pressure release valve (4) and the pilot

select valve (5) are mounted on a valve plate (6) which is

bolted to the sub plate (7) located under the cab. The sub

plate can be swung down for servicing of components or

removed from the cab mount for valve removal.

Follow the procedure in this section to swing down the

sub plate (6) and valve plate assembly (5) from the

vehicle in order to service the main control valve (1),

accumulators (2), accumulator charge/secondary

function valve (3), auxiliary hydraulic pressure release

valve (4) and the pilot select valve (5).

a. Sub Plate w/Valve Plate Lowering

1. Park the vehicle on a firm, level surface, fully retract

all hydraulic cylinders, raise the boom, place the

travel select lever in the [N] NEUTRAL DETENT

position, level the vehicle side to side, 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 access plate from the cab floor to gain

access to the hose and tube fittings on the valve

plate which is located under the cab.

5. Thoroughly clean the main control valve and

surrounding area, including all hoses and fittings,

before proceeding.

6. Label or otherwise mark the hydraulic hoses and

tubes at the main control valve, accumulator charge/

secondary function valve or selector valve. Place a

suitable container to catch hydraulic fluid drainage

beneath the cab.

7. Remove the step assembly from the side of the cab.

Refer to Section 4.5, “Cab Removal,” for step

removal procedure.

8. Check to be sure the two tethers (8) are positioned

in the two mounting tabs (9) on the front and rear

sides of the cab mount. If not, place the loop of the

tether in the mount before proceeding.

9. Place a floor jack (10) under the outer edge of the

sub plate (11) to hold the sub plate in position while

removing the two capscrews (12) and washers (13)

securing the sub plate to the cab support.

MU5950

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.

WARNING: Uncontrolled lowering of the

sub plate assembly can cause personal injury.

ALWAYS support the sub plate before

loosening or removing any mounting hardware.

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Lull 944E-42 Service Manual User Manual Page 428

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