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Kubota KX057-4, U55, U55-4 Excavator Workshop Repair Manual

Kubota KX057-4, U55, U55-4 Excavator Workshop Repair Manual

🚜 Equipment
Brand	Kubota
Type	Excavator
Model	KX057-4, U55, U55-4
📄 Documents
Language	English
Format	PDF
Title	Publication No.	Pages
Repair Manual (English Version)	RY921-20860	739
Repair Manual (French Version)	RY921-20860	798

The Kubota KX057-4, U55, and U55-4 Excavators are high-performance machines designed for power, precision, and operator comfort in demanding construction, utility, and landscaping applications. Built with robust Kubota diesel engines, advanced hydraulics, and versatile work modes, these excavators deliver the strength and reliability required for mid-size excavation projects while maintaining maneuverability in tighter job sites.

The KX057-4 features a 47.6 hp engine with an operating weight of approximately 5.5 tonnes, offering a maximum digging depth of 12’8” (3.87 m) and a reach of 20’1” (6.1 m). It delivers a breakout force of over 9,500 lbs, supported by smooth auxiliary hydraulics for efficient attachment use. The U55 and its updated version, the U55-4, deliver around 45 hp with comparable operating weights of 5.4–5.6 tonnes. They provide digging depths up to 11’10” (3.63 m) and breakout forces exceeding 11,000 lbs. The U55-4 further improves performance with dual adjustable auxiliary circuits, enhanced cab comfort, and refined hydraulic response.

The workshop repair manual provides complete service coverage for these models, including engine, hydraulic circuits, main pumps, control valves, swing and travel motors, electrical systems, and operator cab assemblies. It also includes detailed schematics, wiring diagrams, torque specifications, lubrication schedules, and troubleshooting procedures, ensuring accurate diagnostics and professional servicing.

Key Highlights

KX057-4: 47.6 hp engine, ~5.5 t operating weight, 12’8” digging depth, 20’1” reach
U55: ~45 hp engine, ~5.6 t weight, 11’10” digging depth, 19’6” reach
U55-4: Updated version with improved hydraulics, dual auxiliary circuits, and enhanced cab comfort
Bucket breakout force up to 11,177 lbs depending on model
Auxiliary hydraulics with adjustable flow to support a wide range of attachments
Compact transport width (~1.96 m) for stability and access to confined sites
Repair manual covers engine, hydraulics, electrical, travel/swing motors, pumps, and cab systems
Includes wiring and hydraulic schematics, torque values, and lubrication charts
Designed for easy maintenance, durability, and long service life

Title	Repair Manual (English Version), Repair Manual (French Version)

Table of Content

📙 Table of Contents – Publication Number RY921-20860

- CONTENTS
- TO THE READER
- I INFORMATION
  - INFORMATION
    - 1. SAFETY FIRST
    - 2. IN THE INTEREST OF WORK SAFETY
      - [1] WORKING SAFELY WITH THE EQUIPMENT MEANS ALWAYS FOLLOWING THESE INSTRUCTIONS:
        (1) Precautions Before Working on the Mini-Excavator
        (2) Precautions Before Working on the Equipment
    - 3. LABELS DISPLAYED TO PROMOTE WORK SAFETY
      - [1] LOCATIONS
      - [2] LABEL MAINTENANCE
    - 4. MAIN SPECIFICATIONS
    - 5. DIMENSIONS
- G GENERAL
  - GENERAL
    - 1. CHECKING EXCAVATOR IDENTIFICATION
    - 2. ENGINE IDENTIFICATION
      - [1] MODEL NAME AND SERIAL NUMBER
      - [2] E4B ENGINE
      - [3] CYLINDER NUMBER
    - 3. MUFFLER FULL ASSEMBLY IDENTIFICATION
      - [1] PART NUMBER AND SERIAL NUMBER
    - 4. GENERAL PRECAUTIONS
    - 5. HANDLING PRECAUTIONS FOR ELECTRICAL PARTS AND WIRING
      - [1] WIRING
      - [2] FUSES
      - [3] CONNECTOR
      - [4] WASHING THE MACHINE WITH A HIGH-PRESSURE WASHER
    - 6. TIGHTENING TORQUES
      - [1] TORQUES FOR GENERAL USE NUTS AND BOLTS
      - [2] TORQUE FOR HYDRAULIC HOSE FITTINGS
        (1) Torque for Hydraulic Hose Fittings
        (2) Torques of Lock-Nuts for Elbows with Male Seats and Adaptors with O-rings (Straight Threads)
      - [3] HOSE CLAMP SCREW TORQUE
    - 7. OIL AND WATER CAPACITY TABLE
    - 8. MAINTENANCE INTERVALS
- 1 MACHINE BODY
  - SERVICING
    - 1. FRONT
      - [1] BOOM ASSEMBLY/DISASSEMBLY
      - [2] TABLE OF DIMENSIONS
        (1) Arm
        (2) Blade
    - 2. SWIVEL FRAME
      - [1] WEIGHT ASSEMBLY/DISASSEMBLY
      - [2] CANOPY ASSEMBLY/DISASSEMBLY
      - [3] CABIN REMOVAL AND MOUNTING
      - [4] FUEL TANK ASSEMBLY/DISASSEMBLY
      - [5] HYDRAULIC OIL TANK ASSEMBLY/DISASSEMBLY
      - [6] ASSEMBLY/DISASSEMBLY OF ENGINE RELATED COMPONENTS
        (1) DPF Muffler
        (2) Engine
      - [7] ASSEMBLING OPERATING LEVERS
        (1) Travel Lever
        (2) Blade Lever
        (3) Limit Switch
    - 3. TRACK FRAME
      - [1] SWIVEL BEARING ASSEMBLY/DISASSEMBLY
      - [2] TRACK
        (1) Assembly/Disassembly of the Rubber Track
      - [3] FRONT IDLER
        (1) Assembly/Disassembly of Front Idler
        (2) Disassembly and Assembly
      - [4] GREASE CYLINDER
        (1) Assembly/Disassembly of the Grease Cylinder
        (2) Components
      - [5] TENSIONER
        (1) Tensioner Assembly/Disassembly
        (2) Components
      - [6] TRACK ROLLERS
        (1) Track Roller Assembly/Disassembly
        (2) Disassembly and Assembly
      - [7] CARRIER ROLLERS
        (1) Carrier Roller Assembly/Disassembly
        (2) Components
      - [8] TABLE OF DIMENSIONS
        (1) Rubber Track
        (2) Steel Track
        (3) Idler Sprocket
        (4) Carrier Rollers and Track Rollers
    - 4. MEASURING MACHINE PERFORMANCE
      - [1] MEASURING FRONT PERFORMANCE
        (1) Measuring Swivel Gear Backlash
        (2) Measuring Swivel Bearing Play
    - 5. SWIVEL GEAR BACKLASH PERFORMANCE
- 2 ENGINE
  - GENERAL
    - 1. SPECIFICATIONS
    - 2. DIMENSIONS
    - 3. PERFORMANCE CURVES
- 3 HYDRAULIC SYSTEM
  - MECHANISM
    - 1. HYDRAULIC CIRCUIT DIAGRAM
      - [1] HYDRAULIC CIRCUIT DIAGRAM (KX040-4 STANDARD SPECIFICATIONS (AUX1)
      - [2] HYDRAULIC CIRCUIT DIAGRAM (KX040-4 STANDARD SPECIFICATIONS (AUX1, AUX2)
      - [3] HYDRAULIC CIRCUIT DIAGRAM (KX040-4 ANGLE SPECIFICATIONS (AUX1, AUX2)
    - 2. PUMP
      - [1] SPECIFICATIONS
      - [2] FUNCTION AND STRUCTURE
        (1) Operating Principles
        (2) Horsepower Control
        (3) Flow Control (LS Control)
        (4) Gain Control
        (5) Standby Flow Amount
    - 3. CONTROL VALVES
      - [1] SPECIFICATIONS
      - [2] FUNCTION AND STRUCTURE
        (1) Unload Valve Section
        (2) Spool Section Operation
        (3) Arm Regenerative Function
        (4) Travel Section Operation
        (5) Blade Section Operation
        (6) Anti-Drift Function
        (7) Signal Circuit
    - 4. SWIVEL MOTOR
      - [1] SPECIFICATIONS
      - [2] FUNCTION AND STRUCTURE
        (1) Operating Principles
        (2) Make Up Circuit
        (3) Shockless Valves
        (4) Parking Brake
    - 5. TRAVEL MOTOR
      - [1] SPECIFICATIONS
      - [2] FUNCTION AND STRUCTURE
        (1) Operating Principles
        (2) Counterbalance Valve
        (3) Anti-Cavitation Valve
        (4) Auto-Decelerator Function
        (5) Parking Brake
        (6) Decelerator
    - 6. HYDRAULIC CYLINDER
      - [1] SPECIFICATIONS
      - [2] FUNCTION AND STRUCTURE
        (1) Operating Principles
    - 7. PILOT VALVE
      - [1] CONTROL PILOT VALVES
        (1) Specifications
        (2) Function and Structure
      - [2] TRAVEL PILOT VALVE
        (1) Specifications
        (2) Function and Structure
      - [3] SWING PILOT VALVE
        (1) Specifications
        (2) Function and Structure
      - [4] BLADE PILOT VALVES
        (1) Specifications
        (2) Function and Structure
    - 8. SOLENOID VALVE
      - [1] UNLOAD VALVE
        (1) Specifications
        (2) Function and Structure
      - [2] AUX SOLENOID VALVE
        (1) Specifications
        (2) Function and Structure
      - [3] ANGLE SOLENOID VALVE
        (1) Specifications
      - [4] EP MODE SOLENOID VALVE
        (1) Specifications
  - SERVICING
    - 1. PUMP
      - [1] PUMP DISASSEMBLY / ASSEMBLY
    - 2. CONTROL VALVE
      - [1] REMOVAL AND INSTALLATION OF THE CONTROL VALVE
    - 3. SWIVEL MOTOR
      - [1] REMOVAL AND INSTALLATION OF THE SWIVEL MOTOR
      - [2] SWIVEL MOTOR ASSEMBLY AND DISASSEMBLY
        (1) Disassembly
        (2) Assembly
    - 4. SWIVEL JOINT
      - [1] REMOVAL AND INSTALLATION OF THE SWIVEL JOINT
      - [2] SWIVEL JOINT DISASSEMBLY / ASSEMBLY PROCEDURES
        (1) Disassembly Procedures
        (2) Assembly Procedures
    - 5. TRAVEL MOTOR
      - [1] REMOVAL AND INSTALLATION OF THE TRAVEL MOTOR
      - [2] TRAVEL MOTOR DISASSEMBLY / ASSEMBLY PROCEDURES
        (1) Disassembly
        (2) Assembly
      - [3] SPECIAL TOOLS
    - 6. HYDRAULIC CYLINDER
      - [1] TIGHTENING TORQUE
    - 7. PILOT VALVE (CONTROL)
      - [1] CONTROL PILOT VALVES
        (1) Disassembly
        (2) Assembly
        (3) Special Tools
      - [2] TRAVEL PILOT VALVE
        (1) Disassembly
        (2) Assembly
      - [3] SWING PILOT VALVE
        (1) Disassembly
        (2) Assembly
      - [4] BLADE PILOT VALVES
        (1) Disassembly
        (2) Assembly
    - 8. SOLENOID VALVE
      - [1] UNLOAD VALVE
      - [2] AUX/ANGLE SOLENOID VALVE
      - [3] EP MODE SOLENOID VALVE
    - 9. ROUTING OF HYDRAULIC HOSES
      - [1] TYPES OF HYDRAULIC HOSES
      - [2] HIGH-PRESSURE HOSES
        (1) Deliver Hose Routing
        (2) Front Hose Routing
        (3) Travel, Swivel, Blade, Swing and Angle Hose Routing
        (4) Swivel and Rotary Joint Hose Routing
        (5) Undercarriage Hose Routing
        (6) Hose Routing Inside the Track Frame
      - [3] LOW-PRESSURE HOSES
        (1) Suction Pipe and Hose Routing
        (2) Drain Hose Routing
      - [4] PILOT HOSES
        (1) Port P Hose Routing (1/2)
        (2) Port P Hose Routing (2/2)
        (3) Port T Hose Routing
        (4) Pilot Valve Hose Routing (1/2)
        (5) Pilot Valve Hose Routing (2/2)
        (6) Pilot Valve Hose Routing (Control Valves)
        (7) Pilot Valve Hose Routing (Around the Driver’s Seat)
    - 10. MEASURING HYDRAULIC DEVICE PERFORMANCE
      - [1] PISTON PUMP AIR BLEEDING PROCEDURE
      - [2] RELEASE OF PRESSURE IN THE HYDRAULIC SYSTEM
      - [3] MANUAL BOOM LOWERING PROCEDURE
      - [4] MEASURING THE FLOW RATE
        (1) Measuring Main Pump Flow
        (2) Measuring the AUX Proportional Limit
        (3) Measuring AUX Discharge Flow
      - [5] MEASURING PRESSURE
        (1) Measuring the Main Relief Valve Pressure
        (2) Measuring Pilot Secondary Pressure
        (3) Measuring EP Proportional Solenoid Pressure
        (4) Measuring the Overload Relief Valve Pressure
        (5) Pressure Measuring Kit
        (6) Measuring Swivel Relief Pressure
        (7) Adjusting the LS Control Differential Pressure Adjusting Spring
      - [6] MEASURING SWIVEL PERFORMANCE
        (1) Measuring Swivel Motor Drain Volume
        (2) Measuring Swivel Block Performance
        (3) Measuring Swivel Speed
      - [7] MEASURING TRAVEL PERFORMANCE
        (1) Measuring Travel Motor Drain Volume
        (2) Measuring Travel Block Performance
        (3) Measuring Travel Speed
        (4) Measuring Travel Drift
      - [8] MEASURING CYLINDER SPEED
        (1) Measuring Hydraulic Cylinder Operating Time
        (2) Measuring Hydraulic Cylinder Drift
        (3) Measuring Swing Cylinder Deviation
    - 11. HYDRAULIC DEVICE PERFORMANCE STANDARDS
      - [1] FLOW RATE
        (1) Main Pump Discharge Flow Rate Data (Measured Values)
        (2) Flow Rate Data for AUX Proportional Control (Measured Values)
        (3) AUX Discharge Flow Rate Data (Measured Values)
      - [2] RELIEF PRESSURE (MEASURED VALUES)
      - [3] SWIVEL PERFORMANCE
      - [4] TRAVEL PERFORMANCE
      - [5] CYLINDER SPEED
    - 12. TROUBLESHOOTING
      - [1] TROUBLESHOOTING ALL ACTUATORS
      - [2] TROUBLESHOOTING FRONT SYSTEMS
      - [3] TRAVEL SYSTEM TROUBLESHOOTING
      - [4] SWIVEL SYSTEM TROUBLESHOOTING
- 4 ELECTRICAL SYSTEM
  - SERVICING
    - 1. ELECTRICAL DEVICE LAYOUT AND WIRING CIRCUIT
      - [1] PRECAUTIONS ON HOW TO CLAMP THE ELECTRICAL WIRING
      - [2] PRECAUTIONS ON HANDLING ELECTRICAL CONNECTORS
    - 2. METER PANEL OPERATION
      - [1] NAMES AND FUNCTIONS OF METERS
      - [2] USER SETTINGS MODE
        (1) Log Record
        (2) Periodic Check
        (3) Set Clock
        (4) Set AUX Flow Ctrl
        (5) Various Settings
        (6) Language Setting
      - [3] SERVICE DEALER SETTING
        (1) Crane Mode
        (2) Arm Control Mode (Only on Japan Spec.)
      - [4] SERVICE/DEALER MODE
        (1) Diagnosis
        (2) Setting
      - [5] SETTINGS WHEN REPLACING ELECTRONIC DEVICES
        (1) When Replacing the Meter or Main ECU
        (2) When the Battery is Removed
      - [6] TABLE OF METER PANEL MESSAGES AND ERROR HISTORY LIST
        (1) Red Warning Lamp Lit
        (2) Yellow Warning Lamp Lit
        (3) Other Screens
        (4) PM Clog Level and the State of the Machine
        (5) Table of Engine System Error Numbers
    - 3. INSPECTIONS
      - [1] POWER AND GROUND
      - [2] STARTING AND STOPPING DEVICE
      - [3] RELAY LAYOUT
    - 4. TROUBLESHOOTING (START-UP EQUIPMENT VERSION)
    - 5. METHODS FOR DIAGNOSING ERRORS
      - [1] GUIDE TO DIAGNOSING ERRORS
      - [2] ERROR DIAGNOSIS PROCEDURE
      - [3] TESTING WITH A CIRCUIT TESTER
    - 6. TROUBLESHOOTING (METER PANEL VERSION)
      - [1] MACHINE RELATED SYSTEM
        (1) Engine Oil Pressure Errors
        (2) Charging System Errors
        (3) Fuel Sensor Errors
      - [2] FRONT-END SYSTEMS
        (1) Lever Lock System Errors
        (2) Travel 2-Speed System Error
        (3) Angle System Errors
      - [3] AUTO IDLING (AI) SYSTEM
        (1) AI System Errors
        (2) Testing the AI Pressure Switch
        (3) Testing the AI Switch
      - [4] ANTI-THEFT (AT) SYSTEM
        (1) Anti-Theft System Errors
      - [5] POWER SUPPLY SYSTEM
        (1) Over Voltage
        (2) 5 V Short System Error
      - [6] COMMUNICATION SYSTEM
        (1) CAN Communication Errors
      - [7] MULTIPURPOSE SWITCH
        (1) Multipurpose Switch Control System Errors
      - [8] AUX SYSTEM
        (1) AUX1 / AUX2 (Thumb) System Errors
      - [9] ECO MODE SYSTEM
        (1) EP System Errors
- 5 CABIN
  - MECHANISM
    - 1. AIR CONDITIONING SYSTEM
      - [1] STRUCTURE
      - [2] HOW THE MECHANISMS OF THE SYSTEM WORK
      - [3] COMPRESSOR
      - [4] AIR CONDITIONING UNIT
      - [5] CONDENSER
      - [6] RECEIVER
      - [7] PRESSURE SWITCH
      - [8] ELECTRICAL SYSTEM
        (1) Electrical Circuits
        (2) Relays
        (3) Blower Switch
    - 2. WIPER
      - [1] WIPER SWITCH
      - [2] WIPER
      - [3] WIPER MOTOR
  - SERVICING
    - 1. TROUBLESHOOTING
    - 2. MAINTENANCE AND SERVICE RELATED SPECIFICATIONS
    - 3. TORQUE
    - 4. PRECAUTIONS WHEN REPAIRING THE REFRIGERANT SYSTEM
      - [1] USE OF SERVICE TOOLS
        (1) Manifold Gauge Set
        (2) Refrigerant Charging Hoses
        (3) Vacuum Pump Adapter
        (4) Electric Gas Leak Tester
        (5) Canister Tap Valve
        (6) T-Joint
        (7) R134a Refrigerant Collection/Recycling Device
    - 5. INSPECTING AND CHARGING THE REFRIGERANT SYSTEM
      - [1] CHECKING THE SYSTEM WITH A MANIFOLD GAUGE
      - [2] COLLECTION, VACUUMING AND CHARGING
        (1) Collecting Refrigerant
        (2) Vacuuming Out the System
        (3) Charging from the High-Pressure Side
        (4) Charging from the Low-Pressure Side
        (5) Inspections and Troubleshooting
    - 6. INSPECTION AND DISASSEMBLY
      - [1] CHECKS AND ADJUSTMENTS
        (1) Compressor
        (2) Relays
        (3) Blower Motor
        (5) Blower Switch
        (6) Servo Motor (for Temp Control)
        (7) Pressure Switch
      - [2] DISASSEMBLY AND ASSEMBLY
        (1) Connecting / Disconnecting AC Hoses
        (2) Mounting and Removing the Compressor
        (3) Diagram of AC Hoses
        (4) Mounting and Removal of the Condenser and Receiver
    - 7. WINDOW WASHER
      - [1] WIPER SWITCH
      - [2] WIPER MOTOR
      - [3] WASHER MOTOR
    - 8. REMOVAL AND INSTALLATION OF GLASS
      - [1] PREPARATION
      - [2] REMOVING GLASS
      - [3] INSTALLING GLASS
      - [4] GLASS TRIM TYPE
      - [5] HOW TO REPLACE THE GLASS OF THE RIGHT-SIDE WINDOW
    - 9. FRONT WINDOW
      - [1] ADJUSTING THE CLOSING LOCK OF THE FRONT WINDOW (TOP)
      - [2] ADJUSTING THE OPEN LOCK OF THE FRONT WINDOW (TOP)
- ELECTRICAL CIRCUIT DIAGRAM
- CONNECTOR CHART

Specification

Specification	Kubota KX057-4 Excavator	Kubota U55 Excavator	Kubota U55-4 Excavator
Engine Power	47.6 hp gross / 45.4 hp net	~45 hp net	~45 hp net
Operating Weight	≈ 5.54 t (≈ 12,200 lb) :contentReference[oaicite:0]{index=0}	≈ 5.6 t (≈ 12,335 lb) :contentReference[oaicite:1]{index=1}	≈ 5.4 t (≈ 12,000 lb) :contentReference[oaicite:2]{index=2}
Digging Depth / Reach	Depth ~12 ft 8″ (3.87 m), Reach ~20 ft 1″ (6.1 m) :contentReference[oaicite:3]{index=3}	Depth ~11 ft 10″; Reach ~19 ft 6″ :contentReference[oaicite:4]{index=4}	Depth ~3.63 m; Reach ~6.1 m :contentReference[oaicite:5]{index=5}
Bucket Breakout Force	~9,515 lbf (4,315 kgf) :contentReference[oaicite:6]{index=6}	11,177 lbf (5,071 kgf) :contentReference[oaicite:7]{index=7}	~9,294 lbf (41.35 kN) :contentReference[oaicite:8]{index=8}
Auxiliary Hydraulic Flow	19.9 gal/min (~75 L/min) :contentReference[oaicite:9]{index=9}	~39.4 gpm (implements + swing) :contentReference[oaicite:10]{index=10}	Dual adjustable circuits from panel :contentReference[oaicite:11]{index=11}
Dimensions (Length × Width × Height)	5.52 m × 1.96 m × 2.55 m :contentReference[oaicite:12]{index=12}	Length ~18 ft; Width ~6 ft 5″; Height ~8 ft 4″ :contentReference[oaicite:13]{index=13}	5.5 m × 1.96 m × 2.55 m :contentReference[oaicite:14]{index=14}

Buyer Questions & Answers

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