Caterpillarexcavator

Caterpillar 320D L

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar 320D L is a mid-size (roughly 20 to 22 tonne class) hydraulic crawler excavator built on the long/mass-excavation frame configuration that gives the "L" its name, versus the shorter-tail-swing base 320D. Early and U.S.-market production ran the Cat C6.4 engine with ACERT technology meeting Tier 3 emissions; later-build and non-U.S. machines carry the closely related Cat C6.6 ACERT engine built to Tier 4 Interim/Stage IIIB, both in the same roughly 103 kW (138-140 hp) net power class. Operating weight spans about 20 330 kg (44 820 lb) on the standard configuration up to about 21 900 kg (48 280 lb) depending on counterweight, shoe width, and boom/stick combination. It followed the 320C L in Caterpillar's D-series update and ran in production from roughly 2006 into the early-to-mid 2010s before Caterpillar phased in the C7.1-powered 320D2 L, timing that varied by region. Cat offered it with standard, long, and short stick/boom combinations, standard 600 mm double-grouser or optional 790 mm triple-grouser track shoes, and single-function or tool-control auxiliary hydraulics for attachments.

Within the D-series run, the main change was under the hood: the shift from the C6.4 to the C6.6 ACERT engine tracked tightening emissions rules rather than a redesign of the machine itself, and Caterpillar issued the two engines under a shared specification and service document family, so the rest of the machine, hydraulics, undercarriage, and structure, carried over largely unchanged across more than a dozen factory serial-prefix production blocks. That continuity is exactly why the 320D L still matters in the used and parts market today: high production volume, broad parts commonality with the base 320D, and widely available factory documentation make it one of the easier mid-size Cat excavators to keep running and to source components for, especially compared with newer Tier 4 Final machines carrying more complex aftertreatment. Buyers should still confirm which engine and undercarriage length a specific unit carries before ordering service parts, since the C6.4/C6.6 split and the standard/long configuration both affect fitment.

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 320D L specifications

Engine

Engine model (early production)	Cat C6.4 with ACERT, inline-6 diesel, meets U.S. EPA Tier 3 emissions
Engine model (later production)	Later-build units carry the Cat C6.6 ACERT inline-6, introduced to meet Tier 4 Interim/Stage IIIB emissions ahead of the 2011-2012 regulatory change; same power class as the C6.4
Net power (ISO 9249, at 1800 rpm)	103 kW (138-140 hp), figure rounds slightly depending on source
Gross power	approx. 110 kW (148 hp); reported by several dealer/spec listings alongside the 103 kW net figure
Displacement	6.4 L (389 cu in)
Bore x stroke	102 mm x 130 mm (4.1 in x 5.2 in)
Cylinders	6, inline
Emissions tier	U.S. EPA Tier 3 / EU Stage IIIA on early C6.4-powered units; later C6.6-powered units meet Tier 4 Interim / Stage IIIB

Weights

Operating weight, standard undercarriage	20 330 kg (44 820 lb)
Operating weight, long-undercarriage configurations	approx. 21 200-21 900 kg (46 740-48 280 lb), varies by bucket, counterweight and shoe width
Ground pressure	approx. 35.4-35.9 kPa (5.1-5.2 psi) with optional 790 mm (31 in) triple-grouser shoes; figure varies with shoe width and undercarriage length, not separately confirmed for the standard 600 mm shoe

Dimensions

Transport length	9.44-9.45 m (30 ft 11 in - 31 ft), standard boom/stick
Transport width (over tracks)	3.18-3.20 m (10 ft 5 in - 10 ft 6 in)
Transport height (to top of cab)	3.44 m (11 ft 4 in)
Tail swing radius	2.74-2.75 m (9 ft)
Track shoe width, standard	600 mm (24 in) double-grouser; wider 790 mm (31 in) triple-grouser shoes offered
Ground clearance	0.45 m (1 ft 6 in)
Track gauge	2.2 m (7 ft 3 in)

Performance

Max digging depth, standard stick (2.9 m)	6.69-6.72 m (21 ft 11 in - 22 ft 1 in)
Max digging depth, long stick (3.9 m)	7.66-7.68 m (25 ft 2 in)
Max digging depth, short stick (2.5 m)	6.30 m (20 ft 8 in)
Max reach at ground level, standard stick	9.83-9.86 m (32 ft 3 in - 32 ft 4 in)
Max reach at ground level, long stick	10.76-10.79 m (35 ft 4 in)
Max loading/dump height, long stick	6.94 m (22 ft 9 in)
Max cutting height, long stick	9.94 m (32 ft 8 in)
Max cutting height, standard stick	approx. 9.49 m (31 ft 2 in), single-source figure, verify with dealer
Swing speed	11.5 rpm
Max travel speed	5.5-5.7 km/h (3.4-3.5 mph)
Drawbar pull	approx. 205-206 kN (46 100-46 320 lb)
Gradeability	not consistently documented in available spec sheets for this exact job; verify with dealer

Forces

Bucket digging force	155.6 kN ISO / 137.5 kN SAE (34 980 lb / 30 910 lb), standard stick
Stick digging force	105.6 kN SAE (23 740 lb), standard stick; also reported as approx. 106 kN tear-out force
Digging forces, long/short stick	not separately published in available sources; standard-stick figures above are the only corroborated forces

Service capacities (summary)

Fuel tank	410 L (108 gal)
Hydraulic system	260 L (69 gal)
Engine oil	30 L (8 gal)
Cooling system	25 L (6.6 gal)
Hydraulic pump max flow	205 L/min (54 gal/min)
Hydraulic system relief pressure	35 000 kPa (5 076 psi)

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

320D L fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	30 L (8 US gal)	Cat DEO-ULS or Cat DEO diesel engine oil. Viscosity by climate: SAE 10W-30 for -18 to 40°C (0 to 104°F); SAE 15W-40 for -9.5 to 50°C (15 to 122°F); Cat DEO-ULS Cold Weather SAE 0W-40 for -40 to 40°C (-40 to 104°F) in severe cold. Engine is the Cat C6.4 with ACERT; a C6.6-engine 320D/320D L variant is offered in some markets and may carry different service figures.
Cooling system	25 L (6.6 US gal)	Cat ELC (Extended Life Coolant), factory fill, premixed 50 percent coolant to 50 percent water. Cat DEAC is the acceptable alternative. Never run on plain water.
Fuel tank	410 L (108 US gal)	Distillate diesel fuel meeting the Cat specification for distillate diesel fuel. Ultra low sulfur diesel is used where low emissions or aftertreatment devices require it; low sulfur diesel is acceptable otherwise.
Hydraulic system total (including tank)	260 L (69 US gal)	Cat HYDO Advanced 10, SAE 10W, preferred for -20 to 40°C (-4 to 104°F) ambient. Cat HYDO Advanced 30, SAE 30, for warmer ranges. Acceptable alternates: Cat TDTO, Cat MTO, Cat DEO, or Cat BIO HYDO Advanced where a biodegradable fluid is wanted.
Hydraulic tank	120 L (32 US gal); 138 L (36 US gal) including the suction pipe	Same fluid as the hydraulic system total: Cat HYDO Advanced 10 (SAE 10W) preferred, graded to ambient temperature per the lubricant viscosity chart.
Final drive (each)	10 L (2.6 US gal)	Cat TDTO (Transmission/Drivetrain/Differential Oil). Grade picked by ambient temperature: roughly SAE 30 in temperate climates, lighter SAE 10W in cold climates, and SAE 50 in hot climates.
Swing drive	8 L (2.1 US gal)	Cat TDTO, same viscosity-by-climate selection as the final drives (SAE 10W/30/50 depending on ambient temperature).
Grease (spec only)	n/a - applied at grease fittings per the lubrication schedule	Cat Advanced 3Moly grease, NLGI 2, for general external lubrication points in -20 to 40°C (-4 to 104°F). Cat Ultra 5Moly (NLGI 0/1/2) for colder ranges down to -40°C (-40°F). Cat Arctic Platinum NLGI 0 for extreme cold to -50°C (-58°F). Cat Desert Gold NLGI 2 for hot climates up to 60°C (140°F).

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar 320D L maintenance schedule

Service interval	Tasks
Every 10 h	Check engine oil level and coolant level before starting Drain water and sediment from the fuel system water separator Check hydraulic oil level and inspect for external leaks at hoses and cylinders Grease boom, stick, and bucket linkage pins Check track sag and adjust tension; inspect undercarriage for damage Test travel alarm, seat belt, and cab indicators/gauges (weekly: inspect/adjust belts, grease quick coupler)
Every 250 h	Check engine valve lash on the initial service, then recheck every 1000 hours after Change final drive oil and swing drive oil (initial fill) Replace hydraulic system case-drain and pilot oil filters Grease the swing bearing and check final drive and swing drive oil levels Inspect and adjust drive belts Pull an engine oil sample for fluid analysis
Every 500 h	Change engine oil and filter Replace primary and secondary fuel filters Clean the engine crankcase breather Pull hydraulic oil and coolant (Level 1) samples for analysis Grease boom and stick linkage Clean the fuel tank cap and strainer
Every 1,000 h	Recheck engine valve lash Change swing drive oil and check final drive oil level Replace hydraulic case-drain and pilot oil filters Clean and tighten battery terminals and hold-downs Inspect the ROPS/FOPS structure and mounting hardware for damage or loose bolts
Every 2,000 h	Change hydraulic system oil and replace the hydraulic return filter Change final drive oil Clean the hydraulic tank breather screen Replace the cab air conditioner receiver-drier Lubricate the swing gear Pull an annual Level 2 coolant sample
Every 6,000 h	Change hydraulic system oil at the 3000-hour interval if not already done at 2000 hours Add extended-life coolant extender to the cooling system (or every 3 years) Replace the seat belt on schedule regardless of hours (3 years installed / 5 years from manufacture) Budget a full coolant change around the 12,000-hour/6-year mark Plan an undercarriage condition review at this mileage; track chains are a common wear item by now Have swing bearing play and main hydraulic pump output checked before committing to another long run

Servicing the 320D L beyond the schedule

Predictive Maintenance & Fluid Analysis

Pull an engine oil sample every 250 hours on the C6.4/C6.6 ACERT and watch for fuel dilution, an early warning of the rail-pressure drop and injector bypass issues this engine is known for. Sample hydraulic oil and coolant every 500 hours; contaminated hydraulic oil accelerates spool and swing-motor wear long before symptoms show. When greasing the swing bearing, check the purged grease for bright metal flakes, an early sign of race or ball wear before play develops.

Corrective & Common Repairs

Hard starting and stalling under hydraulic load usually trace to falling common-rail fuel pressure: check the rail pressure relief valve and return-line seals before condemning injectors. Hydraulics that feel strong cold but go soft or hesitate on swing once warm point to a sticking valve spool or overheated oil thinning past worn spool lands; isolate swing from boom, stick, and bucket to narrow it to the swing motor or the main pump. Overheating is almost always debris packed between the hydraulic oil cooler and radiator core, not the thermostat.

Overhaul & Rebuild Points

Track chains on this undercarriage typically need replacement near 5000 hours; rollers and idlers can run well past that in favorable ground, so judge by rail height, flange wear, and pin-and-bushing stretch, not hours alone. Recheck swing bearing play with a dial indicator against spec before returning the machine to service; a knock or chuckle at the seal signals internal race damage. Reset engine valve lash at each 1000-hour interval, and inspect the boom and stick pivot bosses for cracks or prior weld repairs at every major teardown.

Seasonal & Environment Servicing

In cold climates, switch to Cat DEO-ULS Cold Weather 0W-40 engine oil and a colder-rated chassis grease once temperatures drop below about -20°C (-4°F), and keep the ELC coolant at its 50/50 premix, never straight water. In hot, dusty applications, wash the hydraulic oil cooler and radiator core often; packed debris chokes airflow to both at once and drives combined hydraulic and coolant overheating. Sand and rock duty wear undercarriage components faster, so tighten track adjustment and wash off packed material more often than the standard interval.

320D L fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
0110-03 / 0110-04	Engine Coolant Temperature Sensor circuit fault (voltage above normal / voltage below normal); a related 0110-09 covers an abnormal signal update rate.	Corroded or damaged sensor connector, chafed harness wiring, or a failed coolant temperature sensor on the C6.4 ACERT engine.	Inspect the sensor connector and wiring for corrosion or damage before condemning the sensor; confirm with Cat ET.
0091-08	Throttle Position circuit — abnormal frequency, pulse width, or signal pattern from the throttle position sensor, producing erratic idle or acceleration.	Worn or failing throttle position sensor, electrical interference, or a chafed/loose harness connector.	Inspect the sensor and harness for damage or corrosion, recalibrate the throttle, and test or replace the sensor if the fault persists.
2265-03 / 2266-03	Hydraulic Pump No.1 / No.2 Outlet Pressure Sensor — voltage above normal (open circuit or short to supply).	Pressure sensor circuit shorted to supply, damaged harness near the pump, or a failed pressure sensor.	Inspect pump pressure sensor wiring for chafe or shorting, check sensor output against spec, and replace the sensor if out of range.
0167	Alternator/charging system circuit fault.	Failing alternator, loose or corroded battery/charging cable connections, or a blown charging circuit fuse.	Check charging voltage at the battery with the engine running, inspect alternator wiring and connections, and test alternator output.
0600	Hydraulic Oil Temperature Sensor circuit fault.	Failed or drifting hydraulic oil temperature sensor, corroded connector, or chafed wiring.	Inspect the sensor and connector, verify wiring continuity, and replace the sensor if the reading is erratic or out of range.
0094-03 / 0094-04	Fuel Delivery (common-rail) Pressure Sensor — voltage above normal / voltage below normal.	Failed fuel pressure sensor, damaged sensor wiring, or a fuel system restriction affecting the reading on the C6.4 common-rail system.	Check sensor wiring and connector, verify actual rail pressure, and test or replace the sensor if the circuit checks out electrically sound.
0102-03 / 0102-04	Boost/Intake Manifold Pressure Sensor — voltage above normal / voltage below normal.	Corroded sensor connector, damaged sensor, or an air intake leak skewing the boost reading.	Inspect intake piping and connections for leaks, check sensor wiring, and test or replace the sensor.
588-9 / 589-9	Monitor System not communicating (588-9) / Machine ECM not communicating (589-9) — a datalink fault between the cab display and machine controllers.	Corroded or damaged datalink wiring/connectors (often from moisture ingress), or a failed monitor or ECM.	Inspect datalink harness and connectors for corrosion or damage, verify power and ground to the monitor and ECM, and use Cat ET to identify which module has dropped off the datalink.

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

320D L attachments & work tools

Buckets

General-purpose buckets for this 20-ton class machine typically span about 0.5-1.19 m3 (0.65-1.55 cu yd) depending on width and profile; severe-duty and severe-rock buckets are narrower and reinforced, roughly 0.46-1.0 m3 across widths from about 600mm (24 in) up to 1050mm+ (42 in) - varies by configuration/series. Buckets mount on the class's standard 2-pin linkage with an 80mm pin diameter. Pin-on is the standard mount, with a hydraulic pin-grabber coupler commonly fitted for quick tool changes.

Hydraulic hammers

This machine falls in the H130-class hammer bracket (the same bracket also covers the 319-321 range), running roughly 320-600 blows per minute on a minimum carrier flow near 120 L/min (32 gpm). Breaker units built for this size class generally run about 1500-1800 kg operating weight with a 125-140mm chisel/tool diameter. Confirm flow and pressure against the specific hammer's spec plate before fitting, since carrier hydraulic output varies by configuration.

Quick couplers

A hydraulic pin-grabber quick coupler is the common fitment for this size class, actuated by an in-cab switch through a solenoid valve so the operator can change buckets and tools without leaving the seat. Couplers sized for this machine use heavy-duty jaws matched to the standard pin spacing, with a backup mechanical pin lock independent of the hydraulic circuit as a safety redundancy.

Thumbs/grapples

Mechanical and hydraulic thumb kits for this size class pair with buckets from about 450 mm to 1270 mm (18 to 50 in) and mount to the stick alongside the standard bucket linkage. Multi-tine grapples (orange-peel and general rehandling styles) offered for excavators in the 14-31 ton range fit this machine; confirm tine count/spacing against the job, since demolition sorting and log/brush handling call for different tine geometry.

Rippers

A single-shank ripper is a common work tool for this machine, mounting on the standard 2-pin linkage matching the bucket mount pin diameter. It scores frozen ground, hard-pan, or thin rock/asphalt ahead of digging and can double as a root hook or demolition claw. It is not a substitute for a rock bucket in continuous excavation.

Hydraulic-kit notes

The auxiliary valve feeding attachment circuits is a factory option on this machine, drawing off the main pump circuit at roughly 35,000 kPa system pressure and up to 205 L/min per pump. A single-function (one-way flow) circuit suits hammers and vibratory plate compactors. A tool control system option adds double-function and medium-pressure rotating-tool capability needed for grapples, shears, pulverizers, and multi-processors. Verify the actual auxiliary configuration fitted to the unit (single-function vs. tool control, standard vs. medium/high pressure) before ordering a hammer or rotating tool, since this was a factory/dealer-installed option and varies by unit.

All 320D L assemblies by section

Every catalogued assembly group for the Caterpillar 320D L. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Hydraulic System

2887603 Lines Gp-Auxiliary Hydraulic

28***03

Lines Group-Auxiliary Hydraulic; -Medium Pressure

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2687122 Lines Gp-Auxiliary Hydraulic

26***22

Lines Group-Auxiliary Hydraulic; -Medium Pressure

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Implements

2687132 Stick Gp-Hoe

26***32

Stick Group-Hoe; -Long Reach

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Machine Arrangement

2532866 Special Ar

25***66	Option Ar-Hydraulic	1
26***22	Lines Group-Auxiliary Hydraulic; -Medium Pressure	1
26***32	Stick Group-Hoe; -Long Reach	1
28***03	Lines Group-Auxiliary Hydraulic; -Medium Pressure	1

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320D L serial number reference

The PIN plate is a riveted metal tag on the upper structure, usually the front-right side near the cab base; Caterpillar also stamps the PIN into the frame at the same spot so the number survives if the plate is lost or painted over. Read the 17-character PIN as manufacturer code, model code, a 3-letter prefix (e.g. PHX, KGF), then the sequential unit digits; the 3-letter prefix marks the specific production/serial-break block for that machine, not the year by itself. Some prefix blocks share the same 320D/320D L model code but were built with different ACERT engine tiers (C6.4 vs. C6.6) depending on production era and market, so always cross-check the engine serial/rating plate rather than assuming from the model code alone.

Prefix	Identifies	Notes
A6F	320D / 320D L	C6.4 ACERT engine. Covers both the standard and long-undercarriage (L) configuration on one factory parts/service manual block.
A8F	320D L	C6.4 ACERT engine. Early production block, approximately 2007, following on from A6F.
A9F	320D L	C6.4 ACERT engine. Approximately 2007, follows the A8F block.
DHK	320D / 320D L	C6.4 ACERT engine, matching this production era. A secondary listing ties this block to an older 3066 diesel, but that engine belongs to the prior-generation 320/320B/320C family and is not corroborated by Caterpillar's own 320D/320D L specification documentation. Confirm engine on the rating plate before ordering engine parts.
JFZ	320D / 320D L	C6.4 ACERT engine. Covers both standard and long-undercarriage machines; field units reported from roughly 2008-2010 builds.
KGF	320D L	C6.4 ACERT engine. Approximately 2007 build.
KZF	320D / 320D L	C6.6 ACERT engine (not C6.4) — confirmed on Caterpillar's own '320D/320D L (C6.6 Engine)' product listing. Later production block, approximately 2011.
MDE	320D L	C6.4 ACERT engine, matching this production era. A secondary listing ties this block to an older 3066 diesel, but that engine belongs to the prior-generation 320/320B/320C family and is not corroborated by Caterpillar's own 320D/320D L specification documentation. Confirm engine on the rating plate before ordering engine parts.
MGG	320D / 320D L	C6.4 ACERT engine. Approximately 2007 build.
PHX	320D L	C6.4 ACERT engine. Field-reported units mostly from 2007-2008 builds; the block itself may run somewhat wider (roughly 2006-2009) — treat exact end dates as approximate.
SPN	320D / 320D L	C6.4 ACERT engine.
TDH	320D / 320D L	C6.4 ACERT engine. Later production block.

Frequently asked questions

What engine does the Caterpillar 320D L use?

Early and U.S.-market 320D L units run the Cat C6.4 engine with ACERT technology (Tier 3). Later-build and non-U.S. units carry the closely related Cat C6.6 ACERT engine (Tier 4 Interim/Stage IIIB). Both are inline-6 diesels in the same roughly 103 kW (138-140 hp) net power class; confirm which one a specific unit has before ordering engine parts.

What is the operating weight of the Cat 320D L?

Operating weight runs about 20 330 kg (44 820 lb) in the standard configuration up to about 21 900 kg (48 280 lb), depending on counterweight, track shoe width, and boom/stick combination.

What replaced the Caterpillar 320D L?

Caterpillar replaced the 320D L with the 320D2 L, which moved to the Cat C7.1 engine and was phased in starting around 2012, with the rollout timing varying by market.

What 320D L owners discuss

What's the most common engine complaint about the C6.4 ACERT in the 320D L?

Hard starting and stalling under hydraulic load top the list. Owners report a rapid fuel rail pressure drop after priming, which points to a leaking return line or a failing rail pressure relief valve. On higher-hour engines, common-rail injectors start bypassing fuel into the return circuit instead of firing cleanly, which shows up as rough starts and gradual power loss under load. Mechanics working these engines typically check rail pressure and the relief valve first, then move to the injectors if the problem persists. Bad or contaminated fuel accelerates injector wear and is a frequent root cause on machines with a spotty fuel-source history.

Why does the hydraulics feel strong when cold but go soft, or the swing hesitate, once the machine warms up?

This pattern usually points to a sticking valve spool or hydraulic oil that's overheating and thinning out, letting internal leakage past worn spool lands. Owners describe swing that quits mid-cycle and needs a shutdown and restart to work again, even after fresh filters and oil. A quick way to isolate it: run boom, stick and bucket separately from swing. If every function goes weak together, suspect the main pump or main relief valve. If only swing is affected, the swing motor or its control valve is the more likely culprit. Air pulled in through a loose suction line or a partly clogged suction strainer can mimic the same symptoms, so rule those out before condemning the pump.

What usually causes overheating on these machines, and what should be checked first?

Most of the time it's dirt packed between the hydraulic oil cooler and the radiator core, not a bad water pump or thermostat. Because the cooler pack sits in front of the radiator, a clogged cooler chokes airflow to the radiator too, so hydraulic and coolant temperature climb together. Pull the cooler pack and wash it from both sides. After that, check belt tension and the fan drive hub, since a slipping belt or a slow fan drive drops airflow enough to cause the same symptom under load on a hot day. Degraded hydraulic oil or dirty hydraulic filters raise fluid temperature on their own and are worth ruling out on machines with skipped service intervals.

How long does the undercarriage typically last on a 320D L, and what wears first?

Track chains commonly reach roughly 5000 hours before needing replacement, though rollers and idlers can run well past that under lighter duty or favorable ground; some owners report rollers still in service near 10,000 hours. Wear rate depends heavily on what the machine runs in: sand and rock chew through pins, bushings and roller treads far faster than loam or soft clay. Keeping track sag properly adjusted and the undercarriage washed off both slow wear noticeably; loose tension and packed-in debris accelerate it. When inspecting, check rail height, roller and idler flange wear, pin-and-bushing stretch, and grouser height rather than going by hours alone, since actual wear varies a lot by application.

What electrical or sensor faults come up most often on the 320D L?

Charging-system faults are common: an intermittent or out-of-range signal from the alternator sensing circuit throws a code and can leave the battery undercharged over time. Faults tied to communication between the main engine ECM and the cab switch panel also show up, usually traced to a connector or harness issue rather than a bad control module. Engine speed sensor faults are reported too; on the C6.4 there are two speed sensors, one near the fuel injection pump and one near the flywheel, and techs note it isn't always obvious from the factory documentation which one is at fault, so expect to check both. Moisture intrusion at connectors and chafed harness runs behind the cab are the usual root cause behind unexplained, intermittent fault codes on these machines.

How do I check the swing (slew) bearing for wear on this machine?

Park on level ground, extend the stick, and use the boom to lift one track slightly off the ground while a second person watches the gap between the upper structure and the undercarriage for visible vertical movement, or listens for a knock or chuckle at the seal. A dial indicator gives an actual number; typical wear limits on this class of excavator run roughly 1.5 to 3.0 mm (0.06 to 0.12 in) of vertical play depending on the bearing's own spec, so don't judge by feel alone. When greasing, check the waste grease pushed out at the seal for bright metal flakes, which signal internal race or ball wear. A grinding, popping, or clicking sound during slew is a reliable sign of internal damage. Because a failed swing bearing can let the house separate from the undercarriage under load, have your dealer verify any measured play against the machine's actual spec before returning it to service.

What should be checked before buying a used 320D L?

Pull the hour meter and cross-check it against service stickers and the general condition of the machine; low hours on this model generally means under roughly 4000, high hours over roughly 8000. Start the engine cold and watch for excess smoke or blow-by at the oil fill cap, and check for leaks at the engine block and around the injectors. Inspect the full undercarriage: track sag, roller and idler wear, sprocket teeth, and pin-and-bushing stretch, since a full undercarriage replacement is one of the biggest repair costs on a machine this size. Cycle every hydraulic function including swing, and watch for the warm-up softness or swing hesitation owners commonly report on these machines. Check the boom and stick for cracks or repair welds, especially near the pivot bosses, and check swing bearing play as described above. Look over the frame for structural cracks, dents, or prior weld repairs, and ask for maintenance records confirming oil and filter intervals were kept. If there's any structural crack repair, a hydraulic pump that won't hold pressure, or play in the swing bearing beyond spec, have your dealer verify the repair before relying on the machine in service.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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