Caterpillar 320B L
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar 320B L is a mid-size, roughly 20-tonne-class hydraulic crawler excavator built on the long/standard-gauge undercarriage that Cat used as the volume configuration across the 320B line. It runs the Cat 3066T, a mechanically governed, turbocharged direct-injection diesel rated at roughly 103 kW (138 hp) gross and 95-96 kW (128 hp) net flywheel power. Operating weight runs roughly 19.4-20.9 tonnes (about 42,800-46,000 lb) depending on counterweight, bucket, and undercarriage selection. The 320B L was built from around the mid-1990s through the early 2000s, following the earlier 320 / 320 L, and was itself succeeded by the 320C / 320C L around the turn of the 2000s. Alongside the L, Cat marketed the 320B under other undercarriage and gauge variants, including narrow-gauge and severe-duty options, for tight-access and rough-underfoot jobs, plus multiple boom, stick, and bucket combinations for different reach and digging-force needs.
Cat reworked the undercarriage geometry on the B series versus the earlier L-series machines, steepening the track roller frame and removing the ledge where the carbody meets the roller frame so spoil sheds instead of packing in. That shows up in field reports of easier digout in sticky ground. The core driveline stayed conservative: the mechanically injected 3066T carried over largely unchanged rather than jumping straight to electronic engine management, which only arrived with the follow-on 320C. That simplicity is exactly why the 320B L still matters in the used and parts market today: no engine ECM to fault-code, a swing, travel, and hydraulic architecture shared broadly across the 320/322/325 platform of its era, and a large production run that keeps parts, final drives, and swing bearings in wide circulation for owner-operators and rebuild shops still running older fleets.
Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.
Caterpillar 320B L specifications
Engine
| Engine model | Cat 3066T, 6-cylinder turbocharged diesel with direct unit injection |
| Gross power | 134 hp (100 kW) at 1800 rpm |
| Net power | 128 hp (95 kW) at 1800 rpm (ISO 9249 / SAE J1349 / EEC 80/1269) |
| Displacement | 6.37 L (389 cu in) |
| Bore x stroke | 102 mm x 130 mm (4.0 in x 5.1 in) per factory data; other published sources give slightly different rounded figures |
| Emissions | Mechanically governed, direct-injection diesel typical of its 1990s-early-2000s production era; no published emissions tier figure found for this specific model |
Weights
| Operating weight | Varies by undercarriage/counterweight configuration: approx. 19,400 kg (42,770 lb) in the lighter configuration up to 20,620 kg (45,459 lb) with the standard undercarriage |
| Transport weight | Not separately documented; use operating weight figures above for transport planning |
Dimensions
| Transport length | Approx. 9.42-9.43 m (30 ft 11 in), varies slightly with boom/stick option |
| Transport width (over tracks) | 3.18-3.20 m (10 ft 5 in to 10 ft 6 in) |
| Transport height (top of cab) | Approx. 2.94-2.96 m (9 ft 8 in to 9 ft 9 in); shipping height with boom in transport position runs higher, up to about 3.43 m (11 ft 3 in) depending on boom/stick option |
| Tail swing radius | 2.75-2.77 m (9 ft 0 in to 9 ft 1 in) |
| Track shoe width | 800 mm (31.5 in) standard shoe |
| Ground clearance | Approx. 0.47-0.49 m (1 ft 7 in to 1 ft 8 in) |
| Track length on ground / undercarriage length | Approx. 3.65 m (11 ft 11 in to 12 ft 0 in) |
| Track gauge | Approx. 2.38-2.41 m (7 ft 10 in to 7 ft 11 in) |
Performance
| Max dig depth | 7.58-7.59 m (24 ft 10 in to 24 ft 11 in) with the standard boom/stick combination; shorter sticks reduce depth to roughly 5.6-6.6 m depending on option |
| Max reach at ground | 10.36-10.69 m (34 ft to 35 ft) with standard boom/stick; shorter stick options reduce reach to roughly 8.8-9.8 m |
| Max cutting height | 9.75-9.76 m (32 ft) with standard boom/stick, less with shorter stick options |
| Max dump/loading height | 6.7-6.95 m (22 ft 9 in to 22 ft 10 in) with standard boom/stick |
| Swing speed | 10.7 rpm |
| Max travel speed | 5.5-5.6 km/h (3.4-3.5 mph) |
| Max drawbar pull | 177 kN (39,800 lb) |
| Gradeability | Not documented in available spec sheets for this model |
Forces
| Bucket digging force | Not documented in available spec sheets for this model; later 320C/320C L figures use a different engine and hydraulic system and do not apply here |
| Stick/arm digging force | Not documented in available spec sheets for this model |
Service capacities (summary)
| Fuel tank | 340 L (90 gal) |
| Hydraulic system (including tank) | 220 L (58 gal) |
| Engine oil | 20.5 L (5.4 gal) |
| Cooling system | 25 L (6.6-6.7 gal) |
| Swing drive | 6 L (1.6 gal) |
| Final drive (each side) | About 10 L (2.6 gal) |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
320B L fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | 19.3 L (5.1 US gal) service refill; approx. 20.8 L (5.5 US gal) total system fill | Cat DEO (Diesel Engine Oil). SAE 10W-30 for ambient -18C to 40C (0F to 104F); SAE 15W-40 for -9.5C to 50C (15F to 122F). Cat DEO-ULS synthetic blends listed as alternates on later manual revisions for extended temperature range. |
| Cooling system | 25.0 L (6.6 US gal) service refill; approx. 25.4 L (6.7 US gal) total system fill | Cat DEAC (Diesel Engine Antifreeze/Coolant), mixed roughly 50/50 with water for standard protection, richer for extreme cold. Cat ELC (Extended Life Coolant) listed as an alternate on later manual revisions. Do not mix ELC with DEAC. |
| Fuel tank | 340.6 L (90 US gal) service refill; 340.3 L (89.9 US gal) operating spec | No. 2-D diesel fuel meeting ASTM D975 for normal service; No. 1-D diesel recommended in cold ambient below 0C (32F) to aid cold starting. |
| Hydraulic system (total, including tank) | 219.5-220.3 L (58-58.2 US gal), including tank | Cat TDTO (Transmission/Drive Train Oil) SAE 10W as the era-correct hydraulic fill; Cat HYDO SAE 10W listed as an equivalent. Viscosity grade is selected from the ambient-temperature chart in the manual. |
| Hydraulic tank (reservoir only) | Not broken out separately from the system total in sourced documentation for this model | Same fluid as the hydraulic system total above. |
| Final drive (each) | 9.8 L (2.6 US gal) each | Cat TDTO meeting TO-4 spec. SAE 30 for roughly 0C to 35C; SAE 40 for -10C to 40C; SAE 50 for 0C to 50C ambient, following the same TDTO viscosity chart used for the swing drive. |
| Swing drive | 6.1 L (1.6 US gal) | Cat TDTO (TO-4 spec), same viscosity-by-temperature selection as the final drives. |
| Pilot / other circuits | Not listed as a separate refill point; pilot and control circuit draws from the main hydraulic tank | Same fluid as the hydraulic system (Cat TDTO / Cat HYDO). |
| Grease (spec only) | N/A - lubricated per grease fitting, no bulk system capacity | Cat Multipurpose Grease (MPGM), NLGI 2, for standard grease points across the normal ambient range. Cat Advanced 3Moly Grease listed as a heavy-duty alternate for high-load pin and bushing joints. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar 320B L maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 6,000 h |
|
Servicing the 320B L beyond the schedule
Predictive Maintenance & Fluid Analysis
The 3066T is mechanically governed with no engine ECM, so fluid trends carry the diagnostic load instead of fault codes. Pull an engine oil sample at every change to track wear metals from the turbo and injection pump. Sample hydraulic oil ahead of the 2000-hour tank change to judge whether it can run longer, and sample final-drive and swing-drive gear oil for water or metal before seals fail. Watch boost pressure and exhaust smoke trend as the earliest sign of turbo or injector wear.
Corrective & Common Repairs
Slow cycle times and weak digging force on a 320B L usually trace to worn swash plates or barrels in the main hydraulic pumps rather than the valve. Check pump case-drain flow before tearing into the control valve. Final-drive leaks at the sprocket are typically a failed floating duo-cone face seal letting planetary gear oil escape and dirt in; catch it before the gear oil runs dry and takes the coupler and planetaries with it. Grinding or lag in slew is usually swing-bearing or swing-motor bearing wear from grease starvation.
Overhaul & Rebuild Points
At high hours, plan on rebuilding or exchanging the main hydraulic pump and swing motor once case-drain flow and pressure fall outside spec, and budget for swing bearing and gear replacement once backlash exceeds the wear-limit chart. Final drive planetary sets and travel motors are a common mid-life rebuild given the 3066T's torque delivery through the undercarriage. On the engine side, cylinder head, turbocharger, and injection pump reconditioning are the typical top-end overhaul once oil consumption or boost trends fall off, well before a full inframe is justified.
Seasonal & Environment Servicing
The 3066T's mechanical injection starts reliably without ether down to moderate cold, but below that, a block heater and correct-viscosity engine and hydraulic oil for winter reduce cold-start wear on the pump and travel motors. Never mix ether with any other starting aid. Protect the cooling system to the coldest expected temperature with the specified coolant concentration. In hot, dusty, or muddy environments, clean radiator and hydraulic oil cooler fins often, adjust track sag for the ground type, and reseal final drives promptly since packed mud accelerates duo-cone seal wear.
320B L fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| 2302 | Governor (throttle) actuator feedback signal out of range or erratic | Worn or intermittent governor actuator feedback potentiometer, a loose connector at the governor motor, or chafed wiring between the actuator and the machine controller | Key off, inspect and reseat the governor motor connector, check the feedback signal wiring for continuity and chafing, then recheck with the engine running before replacing the governor motor assembly |
| 2301 | Governor actuator feedback signal unstable or intermittent | Same root causes as the related governor feedback fault (worn feedback potentiometer, poor connector contact, or intermittent wiring) at a lower fault threshold | Inspect the governor motor wiring harness and connector pins for corrosion or intermittent contact before replacing the actuator |
| 2201 | Governor actuator feedback sensor circuit open or shorted toward supply voltage | Broken wire, a disconnected plug, or a short to the battery-feed circuit in the governor actuator harness | Check the governor connector and harness for an open circuit or a short to power before condemning the actuator |
| 4202 | Engine speed signal abnormal (speed/magnetic pickup sensor circuit) | A failed or out-of-spec engine speed sensor, or excessive air gap between the sensor and the flywheel/timing gear | Check sensor resistance against spec and verify mounting air gap; replace the speed sensor if resistance reads far outside normal range |
| 1302 | Engine oil pressure below normal | Low engine oil level, a failing oil pressure sensor or its wiring, or a worn oil pump/bearings on a high-hour engine | Shut down and check oil level and sensor wiring first; if both check out, pressure-test the lube system |
| 1303 | Engine coolant temperature above normal | Low coolant level, a plugged radiator core, a weak fan drive, a failed coolant temperature sensor, or a thermostat stuck closed | Check coolant level and radiator fins for debris, verify fan operation, then check the coolant temperature sensor circuit |
| 1304 | Hydraulic oil temperature above normal | Low hydraulic oil level, a clogged oil cooler core, a failing cooler fan, or a relief valve stuck open causing constant heat buildup | Check hydraulic oil level and cooler fins for blockage, verify cooler fan operation, then check the hydraulic oil temperature sensor circuit |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
320B L attachments & work tools
Buckets
320B L uses the 80 mm pin B-linkage shared with the 318-325 B-series family. Factory-style buckets span General Purpose (soft-to-hard, low-to-moderate abrasion), Heavy Duty (moderate-to-hard abrasive material), Heavy Duty Rock (fragmented rock, frozen ground, caliche, highly abrasive), and Ditch Cleaning (wide, shallow bank-forming/finishing buckets); Heavy Duty Rock Ripping buckets are a C-series-only option, not offered for this B-series machine. Capacity runs roughly 0.4-1.5 m3 (0.5-2.0 yd3) and width roughly 450 to 1500 mm (18 to 59 in) depending on GP/HD/HDR selection and source, standard bucket capacity varies by configuration/series. All buckets are pin-on through the 80 mm stick/bucket pins.
Hydraulic hammers
Operating weight is about 20.6-20.9 t (45,500-46,000 lb), placing the 320B L in the 20-22 ton medium breaker class. Typical breaker weight for this class runs roughly 1,800-2,500 kg (4,000-5,500 lb), commonly paired with a box- or top-mount hammer using a 100-140 mm tool/chisel diameter. Stay inside the class rating: an undersized hammer loses productivity, an oversized one risks overloading the boom/stick and factory hydraulics.
Quick couplers
Hydraulic pin-grabber quick couplers built for the 80 mm B-linkage pin fit the 320B L along with siblings across the 318-325 B-series range. Mechanical wedge-style pin-on couplers in the same 80 mm pin size are also common on this class. A hydraulic coupler needs its own double-acting line run off the auxiliary valve; it is not standard-plumbed from the factory.
Thumbs/grapples
Hydraulic pin-on thumbs mount to the stick through the same 80 mm pin and are typically sized 600-900 mm (24-36 in) wide to match the GP/HD bucket range. Rotating grapples for log, rock, or debris handling mount through the coupler and run on a dedicated rotate/clamp circuit, commonly in the 150-180 bar (2,200-2,600 psi) range for this size class. Neither is standard-equipped; both need a double-acting auxiliary circuit added to the factory single auxiliary valve.
Rippers
Single-shank rippers built for the 80 mm B-linkage pin mount directly to the stick, sized for the 318-325 class. They scarify frozen ground, hardpan, light rock, and asphalt ahead of digging. Most single-shank designs need no dedicated hydraulic circuit, working off standard stick geometry rather than a cylinder function of their own.
Hydraulic kit notes
The 320B L carries a standard auxiliary hydraulic valve for optional tool circuits. Published main implement system rating is about 185 L/min (48.9 gpm) per pump, roughly 370 L/min (97.8 gpm) combined, at up to about 340 bar (4,980 psi) relief. Tool circuits run lower than that: rotators/grapples in this class typically sit around 150-180 bar, and hammer relief is normally set well under the main implement pressure to protect the tool; exact factory auxiliary relief isn't published, so set it with the dealer or attachment installer. A single-acting circuit covers a hammer; thumbs and grapples need double-acting (2-way) plumbing.
All 320B L assemblies by section
Every catalogued assembly group for the Caterpillar 320B L. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Electrical And Starting System
1882647 Wiring Gp
| 18***47 | Wiring Group-Generator | 1 |
Frame And Body
1908272 Installation Arrangement
| 19***72 | Installation Arrangement | 1 |
Hydraulic System
9t1817 Filter Group
| 9T***17 | Filter Group; (O) (Bsc) | 1 |
1908269 Generator Ar
| 19***69 | Generator Ar | 1 |
| 19***70 | Generator Arrangement | 1 |
| 19***72 | Installation Arrangement | 1 |
1908270 Generator Arrangement-Hydraulic
| 18***46 | Lines Group-Hydraulic | 1 |
| 18***47 | Wiring Group-Generator | 1 |
| 19***70 | Generator Arrangement | 1 |
1882646 Lines Gp-Hydraulic
| 18***46 | Lines Group-Hydraulic | 1 |
Service Equipment And Supplies
2019908 Film-Enclosure
| 20***08 | Film; (Generator Enclosure)(Enclosure) | 1 |
320B L serial number reference
The PIN plate is a riveted or stamped metal tag on the upper structure, usually front-right near the cab on later machines, or just inside/beside the cab door post on older 1990s units like the 320B L. Read the first three characters after the model code as the prefix (identifies the production block/series), followed by the running serial number, e.g. 4MR00692.
| Prefix | Identifies | Notes |
|---|---|---|
| 4MR | 320B L | Standard 320B L production block, beginning around 1996. Distinct from the 320B's own 3MR block in the shared parts book (320B/320B L are covered in one combined catalog with separate serial sections per nameplate). Fitted with the Cat 3066T turbocharged diesel, about 95 kW (128 hp) net. Exact end-of-block year not documented; confirm with dealer. |
| 6CR | 320B L | 320B L block paired in the combined parts manual with the 320B's own 5BR block. Cat 3066T turbocharged diesel confirmed for this block. A used unit carrying this prefix is recorded as a 1998 model, placing this block around that year. |
| 5GW | 320B L | Separate 320B L parts-catalogue serial block, later than 4MR and before 6CR. Only one thin source ties it to the 320B L - confirm with dealer before relying on it. |
Frequently asked questions
What engine does the Caterpillar 320B L excavator use?
The 320B L runs the Cat 3066T, a turbocharged, mechanically governed direct-injection diesel rated at roughly 103 kW (138 hp) gross and 95-96 kW (128 hp) net flywheel power.
What is the operating weight of a Caterpillar 320B L?
Operating weight runs roughly 19.4-20.9 tonnes (about 42,800-46,000 lb), depending on undercarriage, counterweight, and bucket configuration, so check the specific machine's configuration for an exact figure.
What replaced the Caterpillar 320B L?
The 320C / 320C L succeeded the 320B L around the turn of the 2000s, carrying the 3066T forward with a power update and ATAAC aftercooling before Cat later moved the 320 platform to electronic engine control.
What 320B L owners discuss
What engine powers the 320B L, and is it reliable?
Why does the hydraulic oil run hot after just a few hours of work?
What undercarriage wear should I expect on a 320B L?
The swing drifts or the swing motor keeps failing, what's going on?
Auto-throttle or the engine speed dial acting flaky, is this a common electrical issue?
What should I check before buying a used 320B L?
Is the 320B L still a solid choice for an owner-operator today?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific 320B L part?
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