Jlg 40H Service Manual User Manual download pdf (Page 27)

SECTION 2 - PROCEDURES

3120240 – JLG Lift – 2-7

2.8 CYLINDER CHECKING PROCEDURE.

NOTE: Cylinder checks must be performed any time a cylin-

der component is replaced or when improper system

operation is suspected.

Cylinders Without Counterbalance Valves.

Steer Cylinder and Master Cylinder.

3. Using all applicable safety precautions, activate

engine and fully extend cylinder to be checked. Shut

down engine.

4. Carefully disconnect hydraulic hose from retract port

of cylinder. There will be initial weeping of hydraulic

fluid which can be caught in a suitable container.

After the initial discharge there should be no further

leakage from the retract port.

5. Activate engine and extend cylinder.

6. If cylinder retract port leakage is less than 6-8 drops

per minute, carefully reconnect hose to port and

retract cylinder. If leakage continues at a rate of 6-8

drops per minute or more, cylinder repairs must be

made.

7. With cylinder fully retracted, shut down engine and

carefully disconnect hydraulic hose from cylinder

extend port.

8. Activate engine and retract cylinder. Check extend

port for leakage.

9. If extend port leakage is less than 6-8 drops per

minute, carefully reconnect hose to extend port,

then activate cylinder through one complete cycle

and check for leaks. If leakage continues at a rate of

6-8 drops per minute or more, cylinder repairs must

be made.

Cylinders With Single Counterbalance

Valve.

Lift Cylinder, Telescope Cylinder and Extend- A-Reach Lift

Cylinder.

OPERATE ALL FUNCTIONS FROM GROUND CONTROLS.

1. Using all applicable safety precautions, activate

hydraulic system.

WHEN WORKING ON THE LIFT CYLINDER, RAISE THE BOOM TO

HORIZONTAL AND PLACE A BOOM PROP APPROXIMATELY 1

INCH (2.50 CM) BELOW THE BOOM. DO NOT WORK ON THE CYL-

INDER WITHOUT A SUITABLE PROP IN PLACE. REFER TO FIG-

URE 2-2.

2. After completing the above, shut down hydraulic

system and allow machine to sit for 10-15 minutes.

Turn IGNITION SWITCH to ON, move control switch

or lever for applicable cylinder in each direction,

then turn IGNITION SWITCH to OFF. This is done to

relieve pressure in the hydraulic lines. Carefully

remove hydraulic hoses from appropriate cylinder

port block.

3. There will be initial weeping of hydraulic fluid, which

can be caught in a suitable container. After the initial

discharge, there should not be any further leakage

from the ports. If leakage continues at a rate of 6-8

drops per minute or more, the following cylinder

repairs must be made. If the retract port is leaking,

the piston seals are defective and must be replaced.

If the extend port is leaking, the counterbalance

valve is defective and must be replaced.

4. If no repairs are necessary or when repairs have

been made, carefully reconnect hydraulic hoses to

the appropriate ports.

Table 2-1. Chain Stretch Tolerance.

Chain

Size

Pin To Pin

Measurement

Allowable

Stretch

0.50 in. (1.27 cm) pitch 14 in. (36 cm) or 28 pitches 0.42 in. (1.07 cm)

0.625 in. (1.59 cm) pitch 15 in. (38 cm) or 24 pitches 0.45 in. (1.14 cm)

0.75 in. (1.91 cm) pitch 15 in. (38 cm) or 20 pitches 0.45 in. (1.14 cm)

1 in. (2.54 cm) pitch 14 in. (36 cm) or 14 pitches 0.42 in. (1.07 cm)

1.25 in. (3.18 cm) pitch 15 in. (38 cm) or 12 pitches 0.45 in. (1.14 cm)

1.75 in. (4.45 cm) pitch 14 in. (36 cm) or 8 pitches 0.42 in. (1.07 cm)

2 in. (5.08 cm) pitch 14 in. (36 cm) or 7 pitches 0.42 in. (1.07 cm)

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Jlg 40H Service Manual User Manual Page 27

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