The Bobcat 331 is a compact excavator you'll see trenching for utilities, digging footings, or doing tight-access landscaping work. The service manual is what I keep on the bench when a 331 in this serial range comes in with hydraulic issues, engine problems, or electrical gremlins. People reach for this manual when they're past warranty and need real repair info, not safety stickers and daily checks. If you're trying to keep a 331 earning money instead of sitting dead in the yard, this is the book you want.
What this manual helps you do
- Diagnose hydraulic problems, trace lines, and check pressures on the boom, arm, bucket, and travel circuits
- Follow step-by-step teardown and reassembly of major components like the slew motor, drive motors, cylinders, and control valve
- Troubleshoot electrical issues using wiring diagrams, harness routing, and test procedures for switches, sensors, and gauges
- Set and verify adjustments on controls, tracks, swing, and auxiliary hydraulics after repairs
- Replace and torque critical fasteners correctly when doing engine work, undercarriage repairs, or upper-structure service
Who this is for
This manual is for shop mechanics, field techs, owner-operators, and rental fleets working on a Bobcat 331 in the 512913001-512999999 serial range. If you only want basic operating tips or maintenance intervals, you want the operator's handbook instead, not this workshop manual.
FAQ
Q: Is this a searchable PDF, and can I read the wiring diagrams clearly?
A: Yes, these manuals are typically supplied as searchable PDFs, and the wiring diagrams are usually high enough resolution to zoom in and read pin numbers.
Q: How do I know if it matches my machine?
A: Check your 331's serial plate. If it falls between 512913001 and 512999999, this is the correct service manual series.
Q: Is this the right document if I'm rebuilding hydraulics or doing engine work?
A: Yes. This is the workshop-level service manual, the one you'd use for full diagnostics, teardown, and reassembly.
If your 331's serial number is in that range and you're doing your own repairs, this is the right manual. If it's not, you should skip it and match your exact serial range instead.
📘 Show Index
Table of Contents:
- MAINTENANCE SAFETY
- ALPHABETICAL INDEX
- CONTENTS
- FOREWORD
- SERIAL NUMBER LOCATIONS
- HYDRAULIC EXCAVATOR SERIAL NUMBER
- ENGINE SERIAL NUMBER
- DELIVERY REPORT
- HYDRAULIC EXCAVATOR IDENTIFICATION
- PREVENTIVE MAINTENANCE
- SERVICE SCHEDULE (331 S/N 512913001–512915199)
- SERVICE SCHEDULE (331 S/N 512915200 & Above),(331E 517711001 & Above) & (334 S/N 516711001 & Above)
- LIFTING AND BLOCKING THE EXCAVATOR
- TRANSPORTING THE EXCAVATOR
- ENGINE COVER
- Opening The Engine Cover
- Adjustment Of The Engine Cover Latch
- AIR CLEANER
- FUEL SYSTEM
- Fuel Specification
- Filling The Fuel Tank
- Fuel System Maintenance (331 S/N 512913001–512915199)
- Fuel Filter (331 S/N 512913001–512915199)
- Removing Air From The Fuel System (331 S/N 512913001–512915199)
- Fuel System Maintenance (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Fuel Filter (331 S/N 512915200 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- Removing Air From The Fuel System (331 S/N512915200 & Above), (331E S/N 517711001 & Above)& (334 S/N 516711001 & Above)
- ENGINE LUBRICATION SYSTEM
- Checking Engine Oil
- Replacement Of Oil And Filter
- COOLING SYSTEM
- Coolant Level
- Coolant Replacement
- ALTERNATOR BELT
- ELECTRICAL SYSTEM
- Using A Booster Battery (Jump Starting)
- HYDRAULIC SYSTEM
- Checking And Adding Fluid
- Replacing The Hydraulic Oil
- Replacing The Hydraulic Filter
- Replacing The Drain Line Filter
- SPARK ARRESTOR MUFFLER
- Cleaning The Spark Arrestor Muffler (331 S/N 512913001–512915199)
- Cleaning The Spark Arrestor Muffler (331 S/N512915200 & Above), (331E S/N 517711001 & Above)& (334 S/N 516711001 & Above)
- TRAVEL MOTOR
- Checking The Oil Level (331 S/N 512913001–512913404)
- Draining And Refilling (331 S/N 512913001–512913404)
- Checking The Oil Level (331 S/N 512913405 & Above),(331E S/N 517711001 & Above) & (334 S/N 516711001& Above)
- Draining And Refilling (331 S/N 512913405 & Above),(331E S/N 517711001 & Above) & (334 S/N 516711001& Above)
- LUBRICATION OF THE HYDRAULIC EXCAVATOR
- HEATER AIR FILTER (With Cab Option Only) (331 S/N512913001–512915199)
- HEATER AIR FILTER (With Cab Option Only) (331 S/N512915200 & Above), (331E S/N 517711001 & Above)& (334 S/N 516711001 & Above)
- HYDRAULIC SECTION
- HYDRAULIC SCHEMATICS
- HYDRAULIC SYSTEM TROUBLESHOOTING
- HYDRAULIC SERVICE INFORMATION
- MAIN RELIEF VALVES (Adjustable)
- Checking The Main Relief Valves
- Testing the Blade, Boom Swing, Arm and Boost Circuit Relief Valves
- Testing the Swing Circuit Relief
- Testing The Auxiliary And Bucket Circuit Relief Valve
- Testing The Left Hand Travel Circuit Relief Valve
- Testing The Right Hand Travel Circuit Relief Valve
- Testing The Boom Circuit Relief Valve
- CROSS PORT RELIEF VALVE
- HYDRAULIC PUMP
- Checking the Hydraulic Pump
- Removal And Installation (331 S/N 512913001–512915199)
- Parts Identification (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- Disassembly (331 S/N 512913001–512915199)
- Assembly (331 S/N 512913001–512915199)
- HYDRAULIC CONTROL VALVE (5–Spool)
- Left Travel, Right Travel, Boom, Bucket And Auxiliary
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- Parts Identification
- Disassembly
- Outlet Sections Disassembly
- Outlet Sections Assembly
- Mid Inlet Section Disassembly
- Mid Inlet Section Assembly
- Left Travel, Right Travel and Auxiliary Disassembly
- Left Travel, Right Travel and Auxiliary Assembly
- Boom And Bucket Disassembly
- Boom And Bucket Assembly
- Assembly
- PORT RELIEF VALVES AND MAIN RELIEF VALVES
- Parts Identification
- Port Relief Valve Pressure Setting
- Disassembly
- Assembly
- Adjustment Procedure (Work Port Relief Valves Only)
- MAIN RELIEF VALVES (Adjustable)
- Parts Identification
- Pressure Settings
- Disassembly
- Assembly
- Adjusting The Main Relief Valves
- HYDRAULIC CONTROL VALVE (5–Spool)
- Boost, Arm, Boom Swing, Blade And Swing Section
- Description
- Removal And Installation
- Parts Identification
- Disassembly
- Inlet Section Disassembly And Assembly
- Arm, Boost And Swing Motor Disassembly
- Arm, Boost And Swing Motor Assembly
- Boom Swing Disassembly
- Boom Swing Assembly
- Blade Disassembly
- Blade Assembly
- Assembly
- ACCUMULATOR / PRESSURE REDUCING VALVE (S/N 512913001 – 512918775, 517711001 – 517711159,516711001 – 516711880)
- Description
- Removal And Installation
- Parts Identification
- Disassembly
- Assembly
- ACCUMULATOR / PRESSURE REDUCING VALVE(S/N 512918776 & Above, 517711160 & Above and516711881 & Above)
- Parts Identification
- Disassembly
- Assembly
- ACCUMULATOR / PRESSURE REDUCING VALVE (For All Serial Numbers)
- BUILD UP VALVE
- Description
- Removal And Installation
- Disassembly And Assembly
- AUXILIARY SELECTOR VALVE
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), 331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Disassembly And Assembly
- Port Block
- OIL COOLER
- HYDRAULIC RESERVOIR AND FUEL RESERVOIR
- HYDRAULIC FILTER ASSEMBLY
- BOOM CYLINDER
- Removal And Installation
- Parts Identification
- ARM CYLINDER
- Removal And Installation
- Parts Identification
- BUCKET CYLINDER
- Removal And Installation (Standard And Long Arm)
- Removal And Installation (Extendible Arm)
- Parts Identification
- BLADE CYLINDER
- Removal And Installation
- Parts Identification
- BOOM SWING CYLINDER
- Removal And Installation
- Parts Identification
- EXTENDIBLE ARM CYLINDER
- HYDRAULIC CYLINDER
- JOYSTICK CONTROL CHANGE (331 S/N512913001–512917112 & 334 S/N 516711001–516711270)
- ISO to STANDARD Control Pattern
- STANDARD To ISO Control Pattern
- DRIVE SECTION
- RIGHT CONSOLE COVER (331 S/N 512913001–512915199)
- RIGHT CONSOLE (331 S/N 512913001– 512915199)
- Removal And Installation
- Speed Control Lever Removal And Installation
- Speed Control Lever Adjustment
- Low Speed Position
- High Speed Position
- Blade Control Lever And Cable Removal AndInstallation
- LEFT CONSOLE (331 S/N 512913001– 512915199)
- Control Lock Micro–Switch Removal And Installation
- Gas Spring Removal And Installation
- Removal And Installation
- Lock Lever Removal And Installation
- Lock Lever Adjustment
- Latch Plate Adjustment
- RIGHT CONSOLE COVER (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Removal And Installation
- Arm Rest Removal And Installation
- Gauge Removal And Installation
- RIGHT CONSOLE (331 S/N 512915200 & Above),(331E S/N 517711001 & Above) & (334 S/N 516711001& Above)
- Swing Lock Lever Removal And Installation
- Blade Lever Removal And Installation
- Speed Control Lever Removal And Installation
- Speed Control Lever Adjustment
- LEFT CONSOLE COVER (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Removal And Installation
- Arm Rest Removal And Installation
- Switch Removal And Installation
- Switch Description
- Rear Cover Removal And Installation
- Heater Control Removal And Installation
- LEFT CONSOLE (331 S/N 512915200 & Above), (331ES/N 517711001 & Above) & (334 S/N 516711001 &Above)
- Console And Mount Removal And Installation
- Control Lock Micro–switch Removal And Installation
- Lock Lever Removal And Installation
- Gas Spring Removal And Installation
- Console Removal And Installation
- JOYSTICK
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation Of Right Hand Joystick(331 S/N 512915200 & Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Removal And Installation Of Left Hand Joystick (331S/N 512915200 & Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Troubleshooting
- Parts Identification
- Disassembly
- Assembly
- STEERING LEVERS AND PEDALS
- Removal And Installation
- Adjusting Linkage Rods
- UPPER WORKS AND SWING SECTION
- ENGINE COVER
- SEAT AND SEAT MOUNT
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above). (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- FLOORMAT AND FLOOR PLATE
- REAR FLOOR PLATE
- Removal And Installation (331 S/N 512913001–512915199)
- SWING MOTOR COVER
- TOOL BOX
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- LEFT HAND SIDE COVER
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- RIGHT HAND SIDE COVER
- RIGHT HAND CORNER POST
- LEFT HAND CORNER POST
- COUNTERWEIGHTS
- FRONT ENGINE COVER
- BUCKET (PIN ON)
- BUCKET TEETH
- X–CHANGE™
- Removal And Installation
- Disassembly
- Assembly
- EXTENDIBLE ARM
- Removal And Installation
- Disassembly And Assembly
- ARM
- ARM BUSHINGS
- Arm To Boom Bushing Removal And Installation
- Arm To Bucket And Bucket Link Removal And Installation
- BOOM
- BOOM BUSHING
- BOOM SWING BRACKET
- Removal And Installation
- Hose Installation
- SWING BRACKET BUSHING
- Bushing Removal
- Bushing Installation
- BOOM PIVOT BUSHING
- Bushing Removal
- Bushing Installation
- SWING MOTOR
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Cross Port Relief Valve Parts Identification
- Cross Port Relief Valve Disassembly
- Cross Port Relief Valve Assembly
- Parts Identification
- Disassembly
- Assembly
- SWING MOTOR DRIVE CARRIER
- Removal And Installation
- Parts Identification
- Disassembly
- Assembly
- UPPERSTRUCTURE AND SWING CIRCLE GEAR
- Removal And Installation
- Swing Bearing Removal
- Swing Bearing Installation
- Alignment Pins (Not Threaded)
- CENTER SWIVEL JOINT
- Removal And Installation
- Parts Identification
- Disassembly
- Assembly
- ROPS CANOPY
- CAB
- Removal And Installation
- Heater Removal And Installation (331 S/N512913001– 512915199)
- Heater Removal And Installation (331 S/N 512915200& Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- Heater Disassembly And Assembly (331 S/N512915200 & Above), (331E S/N 517711001 & Above)& (334 S/N 516711001 & Above)
- Front Window Removal And Installation
- Front Lower Window Removal And Installation
- Front Upper Window Removal And Installation (331S/N 512913001–512915199)
- Front Upper Window Removal And Installation (331S/N 512915200 & Above), (331E S/N 517711001 &Above) & (334 S/N 516711001 & Above)
- Door Removal And Installation
- Door Window Removal And Installation
- Left Hand Side Window Removal And Installation
- Right Hand Side Window Removal And Installation
- Right Hand Window Assembly Removal And Installation
- Rear Window Removal And Installation
- CAB/CANOPY REAR COVER
- MAIN FRAME AND TRACKS
- BLADE
- TRACK
- Track Lug Height
- Track Tension Adjustment
- Rubber Track Clearance
- Steel Track Clearance
- Adjustment
- Rubber Track Removal And Installation
- Steel Track Removal And Installation
- TRACK FRAME
- Disassembly And Assembly
- Recoil Spring Disassembly And Assembly
- TRACK IDLER
- Parts Identification
- Disassembly
- Assembly
- TRACK ROLLER
- Parts Identification
- Disassembly
- Assembly
- TRAVEL MOTOR
- Testing (331 S/N 512913001–512913404)
- Removal And Installation
- Parts Identification (331 S/N 512913001–512913404)
- Disassembly (331 S/N 512913001–512913404)
- Assembly (331 S/N 512913001–512913404)
- Parts Identification (331 S/N 512913405 & Above),(331E S/N 517711001 & Above)(334 S/N 516711001 &Above)
- Disassembly (331 S/N 512913405 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- Assembly (331 S/N 512913405 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above
- TRACK DAMAGE IDENTIFICATION
- Cutting Of Steel Cords
- Abrasion Of Embedded Metals
- Separation Of Embedded Metals
- Separation Of Embedded Metals Due To Corrosion
- Cuts On The Lug Side Rubber
- Cracks Of The Lug Side Rubber Due To Fatigue
- Lug Abrasion
- Abrasion Of The Track Roller Side
- Cuts On The Edges Of Track Roller Side
- ELECTRICAL SYSTEM
- ELECTRICAL SCHEMATICS
- TROUBLESHOOTING
- ELECTRICAL SYSTEM
- Description
- Fuses (331 S/N 512913001–512915199)
- Fuse Arrangement (331 S/N 512913001–512915199)
- Electrical Relays And Diodes (S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Fuse Arrangement (331 S/N 512915200 & Above),(331E S/N 517711001 & Above) & (334 S/N 516711001& Above)
- BATTERY
- Removal And Installation
- Servicing The Battery
- ALTERNATOR
- Belt Adjustment
- Removal And Installation
- Alternator Output Test
- Rectifier (Diode) Test
- Alternator Regulator Test
- Parts Identification
- Disassembly And Inspection
- Stator Continuity Test
- Stator Ground Test
- Rotor Continuity Test
- Rotor Ground Test
- Rectifier Continuity (Diode) Test
- Assembly
- STARTER
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Disassembly And Assembly (331 S/N 512913001–512915199)
- Cleaning And Inspection (331 S/N 512913001–512915199)
- Parts Identification (331 S/N 512913001–512915199)
- Parts Identification (331 S/N 512915200 & Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Disassembly (331 S/N 512915200 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- Inspection And Repair (331 S/N 512915200 & Above)& (334 S/N 516711001 & Above)
- Assembly (331 S/N 512915200 & Above), (331E517711001 & Above) & (334 S/N 516711001 & Above)
- FUEL LEVEL SENDER
- Removal And Installation
- Testing
- INSTRUMENT PANEL (331 S/N 512913001–512915199)
- GAUGES
- Removal And Installation (331 S/N 512913001–512915199)
- Bulb Replacement (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- Bulb Replacement (331 S/N 512915200 & Above),(331E S/N 517711001 & Above) & (334 S/N 516711001& Above)
- TIMER (331 S/N 512915200 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- DIODES (331 S/N 512915200 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- Diode Location
- Diode Replacement
- Diode Testing
- CAB ELECTRICAL
- Cab Option (331 S/N 512913001–512915199)
- Cab Option (331 S/N 512915200 & Above), (331E S/N517711001 & Above) & (334 S/N 516711001 & Above)
- HORN
- BUZZER
- ENGINE SERVICE
- TROUBLESHOOTING
- VALVE CLEARANCE
- ENGINE COMPRESSION
- GLOW PLUGS
- Removal And Installation
- Checking The Glow Plug
- FUEL SHUT–OFF SOLENOID
- Adjustment
- Removal And Installation
- Timer Module Removal And Installation
- FUEL INJECTION PUMP
- Checking The Injection Pump
- Removal And Installation
- Timing The Injection Pump
- FUEL INJECTOR NOZZLES
- Removal And Installation
- Checking The Injector Nozzle
- FAN GUARD
- RADIATOR
- MUFFLER
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- AIR CLEANER
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N516711001 & Above)
- ENGINE
- ENGINE FLYWHEEL
- Removal And Installation (331 S/N 512913001–512915199)
- Removal And Installation (331 S/N 512915200 &Above), (331E S/N 517711001 & Above) & (334 S/N 516711001 & Above)
- Flywheel Ring Gear
- CYLINDER HEAD
- Removal And Installation
- Disassembly And Assembly
- Servicing The Cylinder Head
- Top Clearance
- VALVE, VALVE SEAT AND GUIDE
- Checking The Valve Guide
- Reconditioning The Valve And Valve Seat
- Valve Spring
- ROCKER ARM AND SHAFT
- TIMING GEARCASE COVER
- IDLER GEAR AND CAMSHAFT
- Removal And Installation
- Servicing The Camshaft
- Servicing The Idler Gear And Shaft
- TIMING GEARS
- FUEL CAMSHAFT
- Removal And Installation
- Governor
- CRANKSHAFT GEAR
- OIL PUMP
- Removal And Installation
- Oil Pump Service
- Checking Engine Oil Pressure
- Relief Valve
- PISTON AND CONNECTING ROD
- Removal And Installation
- Servicing The Piston And Connecting Rod
- Connecting Rod Alignment
- CRANKSHAFT AND BEARINGS
- Removal And Installation
- Servicing The Crankshaft And Bearings
- CYLINDER BORE
- Checking The Cylinder Bore
- WATER PUMP
- Removal And Installation
- Disassembly And Assembly
- SPECIFICATIONS
- HYDRAULIC EXCAVATOR SPECIFICATIONS
- Machine Dimensions (331 S/N 512913001 & Above) Standard Arm
- Machine Dimensions (331E S/N 517711001 & Above) Extendible Arm
- Machine Dimensions (334 S/N 516711001 & Above) Long Arm
- Lifting Capacity
- WEIGHTS
- CONTROLS
- ENGINE
- ELECTRICAL
- HYDRAULIC SYSTEM
- CYLINDER CYCLE TIME
- SWING SYSTEM
- HYDRAULIC CYLINDERS
- DRIVE SYSTEM
- BRAKES
- UNDERCARRIAGE
- STD TRACK SHOES
- REFILL CAPACITIES
- DIGGING FORCE
- ENGINE SPECIFICATIONS
- Fuel Injection Nozzles
- Fuel Injection Pump
- Cylinder Head
- Valves
- Valve Springs
- Valve Timing
- Rocker Arms
- Camshaft
- Tappet
- Piston Rings
- Pistons
- Connecting Rod
- Oil Pump
- Crankshaft
- Timing Gear
- Thermostat
- Engine Bolt Torque
- Crankshaft Re–Grind Data
- Torque For General Metric Bolts
- FUEL, COOLANT AND LUBRICANTS
- ENGINE OIL SPECIFICATIONS
- ANTI–FREEZE SOLUTION
- DECIMAL AND MILLIMETER EQUIVALENTS
- U.S. TO METRIC CONVERSION
- SERVICE MANUAL REVISION
- 331-1
- 331/334-2
- 331/334-3
- 331/334-4
- 331/331E/334-5
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