Case CX31B Mini Excavator: B-Series 3.1-Ton Tight Tail-Swing Compact
The Case CX31B is a 3.1-ton B-Series mini excavator built for residential, utility, and landscape work where reach matters but the swing arc is constrained. Tier 4 Final emissions, hydrostatic dual-path drive, and a rubber-track undercarriage make it well-suited to tight-quarters jobs that bigger excavators can’t reach.
Where the CX31B fits in the Case excavator line
The CX31B is a 3.1-ton class B-Series mini excavator sitting in the heart of Case’s compact excavator range. The B-Series brought Tier 4 Final emissions compliance and a refreshed cab/control package to the small-class Case excavators, with the tight tail-swing geometry that defines the segment - the upper structure stays within the track footprint through swing, which makes the CX31B viable in spaces where a conventional-tail excavator simply can’t work.
Case CX31B Mini Excavator - Quick Specs
- Class
- 3.1-Ton Mini Excavator
- Generation
- B-Series
- Engine
- Tier 4 Final Compact Diesel
- Aftertreatment
- DPF + DEF/SCR
- Drivetrain
- Hydrostatic Dual-Path
- Undercarriage
- Rubber Track
- Tail Swing
- Tight (within-track)
- Serial Plate
- RH lower cab frame, below windshield
Engine, hydraulics, and drivetrain
The CX31B runs a small Tier 4 Final compact diesel feeding a hydrostatic dual-path drivetrain on a rubber-track undercarriage. Boom, dipper, bucket, swing, and propel functions all draw from a single-section main hydraulic pump with electrohydraulic and mechanical pilot control on the joysticks.
The Tier 4 Final aftertreatment package on this size class typically includes a diesel particulate filter (DPF) for soot capture and an SCR catalyst with DEF dosing for NOx control. Common-rail fuel injection demands clean fuel and tight water separation - dirty fuel is the single most common cause of injector failure on this generation. The hydrostatic drive uses variable-displacement pumps and bent-axis or radial-piston travel motors with planetary final drives feeding the sprockets.
Common service items on the CX31B
- Engine internals: Compact Tier 4 Final diesel - pistons, rings, sleeves, head gaskets. Common-rail injection.
- Aftertreatment: DPF service intervals and regeneration behavior, DEF tank and dosing module, SCR catalyst, EGR cooler.
- Fuel system: Common-rail injectors, lift pump, primary and secondary filters with tight water-separator standards.
- Cooling system: Radiator, water pump, thermostat, fan, charge-air cooler, hoses, belts.
- Hydraulic system: Boom / dipper / bucket / swing cylinder seal kits, main pump rebuild, electrohydraulic control valves, hoses.
- Boom and dipper: Pin and bushing service at every joint, bucket pins, thumb attachment hardware, quick-coupler service.
- Undercarriage: Rubber track inspection and replacement, rollers, idlers, drive sprockets, recoil springs.
- Swing system: Swing motor and reduction gear service, swing bearing inspection, swing brake.
- Electrical / ECU: Engine ECU, instrument cluster, sensors, harness, telematics module on equipped units.
- Cab glass and wipers: KHN16820 24-inch wiper blade, KHN3046 front lower glass, and KHN2632 front upper glass cross-fit across Case and Link-Belt excavators.
- Operator station: Seat, joystick controls, pedal linkage, instrument panel, cab HVAC.
Parts we carry for the Case CX31B
| Category | Common Parts | Browse |
|---|---|---|
| Engine | Tier 4 Final diesel internals, gaskets, rebuild kits | Browse Engine |
| Aftertreatment | DPF, DEF dosing, SCR, EGR components | Browse Aftertreatment |
| Fuel System | Common-rail injectors, lift pump, filters | Browse Fuel System |
| Cooling | Radiator, water pump, charge-air cooler, hoses | Browse Cooling |
| Hydraulics | Main pump, swing motor, cylinders, seal kits, valves | Browse Hydraulics |
| Boom / Dipper | Pins, bushings, bucket and quick-coupler hardware | Browse Boom / Dipper |
| Undercarriage | Rubber tracks, rollers, idlers, sprockets | Browse Undercarriage |
| Swing | Swing motor, reduction gear, swing bearing | Browse Swing |
| Cab Glass / Wiper | KHN16820 wiper, KHN3046 lower glass, KHN2632 upper glass | KHN16820 Wiper Blade |
| Electrical / ECU | ECU, sensors, harness, instrument cluster | Browse Electrical |
| Operator Station | Seat, joysticks, pedal linkage, gauges | Browse Operator Station |
Need a part for your Case CX31B Mini Excavator?
Common-rail injection components, hydraulic pumps, and aftertreatment parts are the highest-value items on a CX31B. Call our parts team with your serial number and we’ll match the right component to your machine.
Request a PartWhat to verify before ordering
- Serial number. Confirm the machine serial - the B-Series had running changes through production.
- Engine serial. Engine internal parts must match the engine serial number.
- Hydraulic cylinder bore. Cylinder seal kit fit depends on bore dimension - measure before ordering.
- Tier 4 emissions revision. DPF and DEF/SCR components saw revisions during production - confirm by serial.
- Engine ECU calibration. Common-rail injectors and ECU sensors are calibrated to specific build years.
- Bucket and quick coupler. Quick-coupler interface varies - confirm before ordering attachment-side hardware.
- Rubber track size. Verify track width and link count - the small-class machines have multiple rubber-track options.
Why the CX31B still earns a paycheck
The Case CX31B is sized for compact-excavator duty cycles where a 3.1-ton machine is the right tool - residential landscape, utility, irrigation, plumbing, and any tight-quarters digging where larger excavators won’t fit. Tier 4 Final emissions compliance, compact footprint, and rubber-track flotation suit residential and contractor work where a wheeled or larger tracked machine would mark up turf or fail to fit through gates.
Maintenance priorities on a CX31B: clean fuel with tight water separation for common-rail injection, DPF regen behavior tracking and DEF quality discipline, hydraulic oil at temperature with clean filtration, rubber-track tension and wear monitoring, and pin and bushing service at every working joint. Broken Tractor maintains parts coverage across the Case mini excavator family alongside the broader CX line.
