JLG 660SJ Service Manual (English)

Other manuals for JLG 660SJ

Questions and Answers:

M
Mr. Jeffrey LambJul 27, 2025
How to troubleshoot a JLG Lifting Systems that won’t shift or is slow to start?
- J
  James PhillipsJul 27, 2025
  If your JLG Lifting System won’t shift or is slow to start, it could be due to obstructed or restricted flow through the servo control signal lines, which could result in slow shift or no shift motor conditions. Ensure the signal lines are not obstructed or restricted and that the signal pressure is adequate to shift the motor. Also, supply and drain orifices determine motor shift, and obstruction increases shift times. Ensure proper control orifices are installed in the motor and are not obstructed; clean or replace them if necessary.
D
David AnthonyAug 3, 2025
Why is my JLG 660SJ Boom Lifts system operating hot?
- B
  Bryan BrockAug 3, 2025
  Your JLG Boom Lifts system might be running hot due to several reasons. It could be due to an insufficient amount of hydraulic fluid, which fails to meet the system's cooling demands. In this case, fill the reservoir to the proper level. Another cause might be a failing or obstructed heat exchanger, which also prevents adequate cooling. Make sure the heat exchanger is receiving enough air flow and is in good condition; repair or replace it if needed. Finally, a system relief valve that's unseated for too long or malfunctioning could cause overheating. Repair or replace any faulty relief valves and check that the machine's loads aren't too high.
L
Lisa LeeAug 8, 2025
Why is there excessive noise and vibration in my JLG Lifting Systems?
- B
  Brittney PattersonAug 8, 2025
  Excessive noise and vibration in JLG Lifting Systems can stem from several issues. Insufficient hydraulic fluid may cause cavitation. To resolve this, fill the reservoir to the correct level and ensure the oil supply to the motor is adequate and unobstructed. Trapped air in system lines or the motor can also lead to cavitation; ensure all system lines and components are purged of air. A loose or incorrect shaft coupling will produce vibrations; ensure the correct coupling is used and properly fitted on the shaft. Misaligned shafts create frictional vibration; ensure shafts are properly aligned. Finally, if the viscosity is above acceptable limits, it will result in cavitation; replace the hydraulic oil with the appropriate fluid for the operating conditions.
L
Leslie FitzgeraldAug 15, 2025
What to do if my JLG Lifting Systems are operating hot?
- R
  robert46Aug 15, 2025
  A JLG Lifting System may overheat due to several reasons. An insufficient amount of hydraulic fluid will not meet system cooling demands, so ensure you fill the reservoir to the proper level. Also, if the heat exchanger is failing or obstructed, it may not meet system cooling demands. Make sure the heat exchanger is receiving adequate airflow and is in good operating condition; repair or replace it as necessary. Finally, if a system relief valve becomes unseated for an extended period or fails, the system could overheat. Repair or replace any malfunctioning relief valves and verify loads on the machine are not excessive.
R
Robert BauerAug 20, 2025
How to fix excessive noise and vibration in JLG Boom Lifts?
- B
  Betty ObrienAug 21, 2025
  Excessive noise and vibration in your JLG Boom Lifts can stem from several issues. Insufficient hydraulic fluid can cause cavitation, leading to system noise; ensure the reservoir is filled to the correct level and that oil supply to the motor is adequate and unobstructed. Trapped air in system lines or the motor can also cause cavitation; make sure all system lines and components are purged of air. A loose or incorrect shaft coupling can produce vibrations; verify the correct coupling is used and fits properly. Misaligned shafts create frictional vibration; ensure shafts are properly aligned. Finally, hydraulic oil viscosity above acceptable limits can cause cavitation; replace the hydraulic oil with the appropriate fluid for your operating conditions.

JLG 660SJ Specifications

General

Platform Height	66 ft
Working Height	72 ft
Platform Capacity - Unrestricted	500 lbs
Machine Width	8 ft 2 in
Machine Height	9 ft 10 in
Drive Speed - 4WD	3.5 mph
Gradeability - 4WD	45%
Engine Type	Diesel
Swing	360° Continuous
Platform Rotator	180°
Ground Clearance	1 ft
Fuel Tank Capacity	30 gal
Maximum Platform Height	66 ft
Engine Power	74 hp
Drive Speed	3.5 mph
Platform Capacity - Restricted	750 lbs
Platform Capacity	500 lbs

Summary

SECTION A - INTRODUCTION - MAINTENANCE SAFETY PRECAUTIONS

A GENERAL

General safety precautions for aerial platform maintenance.

B HYDRAULIC SYSTEM SAFETY

Safety precautions for high-pressure hydraulic systems.

C MAINTENANCE

General safety guidelines and warnings for maintenance tasks.

SECTION 1 - SPECIFICATIONS

1.1 CAPACITIES

Details fluid capacities for various machine systems.

1.2 COMPONENT DATA

Provides technical data for engine and other components.

1.6 LUBRICATION

Details lubrication specifications for various components and intervals.

1.7 PRESSURE SETTINGS

Lists hydraulic system pressure settings for various functions.

1.10 CRITICAL STABILITY WEIGHTS

Lists critical weights essential for machine stability and safety.

1.11 LUBRICATION AND OPERATOR MAINTENANCE

Outlines lubrication points, specifications, and maintenance intervals.

SECTION 2 - GENERAL

2.1 MACHINE PREPARATION, INSPECTION, AND MAINTENANCE

Covers general guidelines for machine readiness, inspections, and maintenance programs.

2.2 SERVICE AND GUIDELINES

Provides general information on servicing, safety, and component handling.

SECTION 3 - CHASSIS & TURNTABLE

3.1 TIRES & WHEELS

Covers tire inflation, damage, replacement, and wheel installation procedures.

3.2 DRIVE TORQUE HUB

Details roll, leak, and brake testing, and tightening/torquing bolts.

3.8 SWING BEARING

Details turntable bearing mounting bolt checks and wear tolerances.

3.9 SWING BRAKE - MICO

Covers disassembly, inspection, and assembly of the swing brake.

3.10 ROTARY COUPLING

Procedure for installing the seal kit for the rotary coupling.

3.11 GENERATOR

Maintenance schedule for the generator brushes and slip rings.

SECTION 4 - BOOM & PLATFORM

4.1 BOOM ROPE TORQUING PROCEDURES

Details the procedure for torquing boom rope adjusting nuts.

4.2 WEAR PADS

Covers wear pad inspection and replacement for the main boom.

4.3 WIRE ROPE

Provides daily inspection procedures and criteria for wire rope replacement.

4.4 BOOM MAINTENANCE

Covers removal procedures for platform support, rotator, slave cylinder, and powertrack.

4.5 ARTICULATING JIB BOOM

Details removal, disassembly, inspection, and assembly of the articulating jib boom.

4.6 LIMIT SWITCHES AND CAM VALVE ADJUSTMENT

Instructions for adjusting limit switches and cam valves.

SECTION 5 - HYDRAULICS

5.1 CYLINDERS - THEORY OF OPERATION

Explains the operation of double-acting and holding valve cylinders.

5.2 CYLINDER CHECKING PROCEDURE

Outlines procedures for checking cylinders with and without counterbalance valves.

5.3 CYLINDER REMOVAL AND INSTALLATION

Details removal and installation procedures for main boom telescope and lift cylinders.

5.7 PRESSURE SETTING PROCEDURES

Details procedures for setting hydraulic system pressures for various functions.

5.8 HYDRAULIC COMPONENT START-UP PROCEDURES AND RECOMMENDATIONS

Provides guidelines for starting up hydraulic components after installation or replacement.

SECTION 6 - JLG CONTROL SYSTEM

6.1 INTRODUCTION

Introduces the JLG Control System, its benefits, and analyzer usage.

6.3 USING THE ANALYZER

Explains how to navigate and interpret the analyzer display and menus.

6.5 ADJUSTING PARAMETERS USING THE HAND HELD ANALYZER

Guide on adjusting personality settings and parameters via the analyzer.

6.8 MACHINE PERSONALITY SETTINGS

Details personality ranges and default settings for various machine functions.

SECTION 7 - BASIC ELECTRICAL INFORMATION & SCHEMATICS

7.2 MULTIMETER BASICS

Explains basic multimeter usage: grounding, backprobing, min/max, polarity, scale, voltage/resistance.

7.3 APPLYING SILICONE DIELECTRIC COMPOUND TO ELECTRICAL CONNECTIONS

Details the procedure and reasons for applying silicone dielectric compound to electrical connections.

7.4 AMP CONNECTOR

Covers applying silicone dielectric compound and assembly/disassembly of AMP connectors.

7.5 DEUTSCH CONNECTORS

Procedures for DT/DTP and HD30/HDP series Deutsch connector assembly and disassembly.

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JLG 660SJ Service Manual

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