Caterpillar 345B II
Caterpillarexcavator

Caterpillar 345B II

Maintenance schedule, common problems & OEM parts breakdown

The Cat 345B Series II is a heavy production-class crawler excavator in the 44 to 49 tonne (about 97,000 to 108,000 lb) operating weight bracket, sized above the 330 class and below Cat's largest mining-support excavators. Every 345B Series II carries the Cat 3176C ATAAC inline-six, a 10.3 L turbocharged-and-aftercooled diesel rated 257 kW (345 hp) gross and 239 kW (321 hp) net at the flywheel, meeting EPA Tier 2/ADEM II emissions. Cat built the Series II generation roughly from 2001 to 2005 as the direct update to the original 345B (Series I), then replaced it in 2005 with the 345C L. The Series II shipped off one base chassis in several factory fronts: a standard boom/stick, a mass-excavation (LME) build for quarry loading and larger buckets, a long-reach front for extended digging depth, and an MH material-handler variant.

Across the Series II run Cat carried the 3176C powertrain and pilot-hydraulic implement controls unchanged, so most of the variation between individual machines comes from boom, stick, and undercarriage combination rather than a mid-cycle engine or control-system swap; operating weight, hydraulic flow, and reach shift by several tonnes and a meter or more depending on which front and undercarriage a given unit left the factory with. That shared architecture is what keeps the 345B II relevant in the used and parts market today: the 3176C engine, TDTO-lubricated final and swing drives, and pilot-valve implement circuit are common across the whole Series II line, so a parts book or fluid-analysis baseline built on one configuration largely carries over to the others. In the used market it sits as a mechanically simpler, lower-cost alternative to the ACERT-engined 345C and 345D, with no exhaust aftertreatment to maintain and a well-established parts supply.

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 345B II specifications

Engine

Engine modelCat 3176C ATAAC, inline-6, turbocharged, air-to-air aftercooled
Gross power257 kW (345 hp) at 2000 rpm
Net power239 kW (321 hp) at 2000 rpm, ISO 9249 / SAE J1349
Displacement10.3 L (628.6 cu in), bore 125 mm (4.92 in) x stroke 140 mm (5.51 in)
Cylinders6, in-line, 4-stroke diesel
Emissions / fuel systemMeets EPA Tier 2; electronic (ADEM II) fuel injection control

Weights

Operating weight, standard boom/stickapprox. 44.4-44.5 t (97,900-98,000 lb), long-undercarriage chassis
Operating weight, mass-excavation/long-reach configurationapprox. 48.9-51.3 t (108,000-113,100 lb); heavier with longer boom-stick combinations
Ground pressureapprox. 90 kPa (13.1 psi) on standard shoes

Dimensions

Transport lengthapprox. 11.5 m (37'9"), varies with boom/stick fitted
Transport width2.99-4.33 m (9'10"-14'2"), varies with undercarriage gauge and track shoe width
Transport height, to cab top3.66-3.69 m (12'0"-12'1")
Tail swing radius3.66 m (12'0")
Track shoe width900 mm (36 in) standard triple-grouser; 750 mm (30 in) optional
Ground clearance0.73 m (2'5")
Track (undercarriage) length5.37 m (17'8")

Performance

Max dig depth7.2 m (23'7") with standard mass-excavation stick, up to 9.3 m (30'6") with longer reach stick; varies by boom/stick configuration
Max reach at ground level11.3 m (37'0") standard, up to 13.0 m (42'8") with reach boom and stick
Max dump heightapprox. 7.2 m (23'8") with standard mass-excavation stick
Swing speed8.6 rpm
Max travel speed4.4 km/h (2.8 mph)
Gradeability70% (35 degrees)
Drawbar pull331 kN (74,400 lbf), long-undercarriage chassis

Forces

Bucket digging force232-261 kN (52,200-58,700 lbf), depending on boom type (Reach vs Mass boom)
Arm (stick) digging force156-198 kN (35,100-44,500 lbf), depending on stick length; shorter stick gives higher force

Service capacities (summary)

Fuel tank720 L (190 gal)
Hydraulic system520 L (137 gal) total, including 208 L (55 gal) tank
Engine oil30 L (7.9 gal)
Cooling system45 L (12 gal)

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

345B II fluids & capacities

SystemCapacityRecommended fluid
Engine crankcase (with filter)30 L (7.9 US gal)Cat DEO or Cat DEO-ULS multigrade diesel engine oil. Viscosity by ambient temperature: SAE 10W-30 for -18°C to 40°C (0°F to 104°F), SAE 15W-40 for -9.5°C to 50°C (15°F to 122°F). Cat DEO SYN (5W-40) or Cat Arctic DEO SYN (0W-30) for cold-start service down to -40°C (-40°F).
Cooling system45 L (12 US gal)Cat ELC (Extended Life Coolant) preferred, or Cat DEAC (Diesel Engine Antifreeze/Coolant). The air-to-air aftercooled 3176C engine needs a minimum 30% glycol content to prevent water pump cavitation. A 1:1 water-to-glycol mix gives freeze protection to about -37°C (-34°F); raise glycol percentage for colder climates.
Fuel tank720 L (190 US gal)No. 2-D distillate diesel meeting Cat fuel spec, or No. 1-D winter-blend fuel in cold climates. Minimum cetane number 40.
Hydraulic system total (including tank)520 L (137 US gal)Cat HYDO Advanced 10 (SAE 10W) preferred for -20°C to 40°C (-4°F to 104°F) ambient. Alternates by climate: Cat HYDO, Cat TDTO, Cat DEO/DEO-ULS, or Cat MTO, spanning SAE 0W-20 in extreme cold up to SAE 15W-40 in hot climates.
Hydraulic tank210 L (55 US gal)Same Cat HYDO Advanced 10 / HYDO / TDTO family as the hydraulic system total, matched to ambient temperature.
Final drive (each)15 L (4.0 US gal)Cat TDTO (Transmission/Drive Train Oil) meeting the Cat TO-4 spec. Viscosity by climate runs SAE 0W-20 in extreme cold up to SAE 50 in hot climates per Cat's final drive/swing drive viscosity chart for track-type hydraulic excavators.
Swing drive9.9-11 L (2.6-2.9 US gal) - varies by configuration/seriesSame Cat TDTO TO-4 family as the final drive, viscosity matched to ambient temperature.
Grease (chassis, pin joints, swing gear) - spec onlyN/ACat Multipurpose Grease (NLGI 2) for general chassis and pin joints under moderate loads and temperatures. Cat Advanced 3Moly Grease for heavily loaded boom/stick/bucket linkage pins. Cat Ultra 5Moly Grease for the swing gear/ring - its tacky calcium-sulfonate-complex formulation clings to the vertical swing gear face and resists galling better than standard grease.

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

Caterpillar 345B II maintenance schedule

Service intervalTasks
Every 10 h
  • Check engine oil level before starting and top off with Cat DEO 15W-40 as needed
  • Drain water and sediment from the fuel tank and water separator
  • Check hydraulic oil level with the machine level and implements retracted
  • Weekly (50h): grease boom, stick, and bucket linkage pins; shorten the interval in wet or abrasive ground
  • Weekly (50h): grease the swing bearing and check track tension and shoe bolts for looseness
  • Weekly (50h): walk the machine down for hydraulic leaks at the main control valve and cylinder rod seals
Every 250 h
  • Change engine oil and filter on the 3176C using Cat DEO 15W-40
  • Inspect and adjust fan and alternator belt tension
  • Check swing drive and final drive gear oil levels
  • Clean or replace the primary fuel filter element
  • Grease the swing bearing per the full lube chart, not just the weekly points
  • Inspect the A/C compressor belt and clear debris from the condenser
Every 500 h
  • Replace the secondary fuel filter/water separator element
  • Replace the hydraulic pilot and return-line filters
  • Pull S·O·S samples from engine oil, hydraulic oil, and both final drives
  • Test coolant sample and concentration
  • Load-test the battery and clean terminals and earth straps
  • Check the primary air filter element and replace if the restriction indicator trips
Every 1,000 h
  • Check and adjust engine valve lash on the 3176C
  • Change final drive and swing drive gear oil with Cat TDTO
  • Replace the secondary (inner) air filter element
  • Clean the engine crankcase breather
  • Inspect the turbocharger and ATAAC aftercooler core for leaks or fouling
  • Torque-check swing bearing bolts and track shoe bolts
Every 2,000 h
  • Change hydraulic system oil across the full system (roughly 520 L)
  • Replace the hydraulic tank breather/filler element
  • Flow- and pressure-test the main hydraulic pump and control valve for internal wear
  • Inspect fuel injectors and recalibrate if S·O·S or ECM data flags wear
  • Check alternator, starter, and wiring harness condition
  • Re-torque structural bolts at the boom foot, counterweight, and swing bearing
Every 6,000 h
  • Change coolant on the extended-life interval if running Cat ELC; sooner on conventional coolant
  • Send boom, stick, and bucket linkage pins and bushings for wear-dimension inspection against OMM tolerances
  • Inspect and reseal the swing motor and main pump at the major overhaul threshold
  • Rebuild or replace pilot control valves and joysticks showing response drift
  • Replace the seat belt regardless of hours if webbing shows wear or UV damage

Servicing the 345B II beyond the schedule

Predictive Maintenance & Fluid Analysis

Run S·O·S sampling on the 3176C engine oil, the roughly 520 L hydraulic system, and both final/swing drive gearboxes on the same interval as the fluid changes; the ATAAC turbo and aftercooler show early wear through soot and fuel-dilution trends before any power loss is felt. Pull ECM fault history through Cat ET at every service. Because implement control on this machine is pilot-hydraulic rather than electronic, joystick response and pilot-pressure drift are mechanical wear, not ECM codes, so track them separately in your service log.

Corrective & Common Repairs

Most corrective work on the 345B II traces to the pilot control valve and joystick assemblies; sluggish or drifting implement response is a pilot-circuit wear issue, not an electronic fault, on this generation. Expect turbocharger and ATAAC aftercooler core repairs on high-hour 3176C engines, plus main control valve spool wear from contaminated hydraulic oil. Undercarriage wear on the 900 mm shoes, rollers, and idlers is routine at this weight class; replace before pin and bushing wear reaches the OMM scrap limit to avoid chain and sprocket damage.

Overhaul & Rebuild Points

At major overhaul hours, prioritize the 3176C top end (injectors, turbocharger, cylinder head) and the main hydraulic pump and control valve, since both carry the full digging load of a 44 to 49 tonne machine. Check swing bearing and swing drive gear condition against OMM wear tolerances before committing to a full rebuild; bearing play here also shortens boom and stick pin life. Undercarriage rebuild (rollers, idlers, sprockets, track chain) is typically the single highest-cost line item on a used 345B II and should be quoted before purchase, not after.

Seasonal & Environment Servicing

Verify the 3176C's ether-assist cold-start system and coolant concentration each fall; confirm the starting aid works before the first hard freeze, not after a failed start. Switch hydraulic oil viscosity grade for the season if the machine works outside the OMM's ambient temperature band for its standard fluid. In hot, dusty, or abrasive ground, shorten the grease interval on the boom, stick, and bucket pins and the swing bearing, and check the ATAAC aftercooler core and radiator fins for packed debris that cuts cooling capacity.

345B II fault codes & troubleshooting

CodeMeaningLikely causeWhat to do
100-1Engine oil pressure reading below normal range - low oil pressure warningLow oil level, worn oil pump, plugged filter, or a failing oil pressure sensor/wiringCheck oil level and filter condition first, then verify sensor wiring and connector before replacing the sensor
110-0Engine coolant temperature reading above normal range - high coolant temperature warningLow coolant level, plugged radiator/core, failed fan drive, or a faulty coolant temperature sensorCheck coolant level and radiator for debris, confirm fan operation, then check sensor circuit
111-1Engine coolant level reading below normal range - low coolant level warningCoolant leak in the system or a failed coolant level sensor/probeInspect for external or internal coolant leaks, top off coolant, then verify sensor operation
94-1Fuel delivery pressure reading below normal range - low fuel pressure warningClogged fuel filter, restricted fuel supply line, failing transfer pump, or air in the fuel systemReplace fuel filters, check supply lines for restriction, and bleed air from the system before condemning the transfer pump
190-2Engine speed/timing sensor signal erratic, intermittent, or incorrectDamaged sensor tip clearance, loose sensor, chafed harness, or connector corrosion at the speed/timing sensorCheck sensor air gap and mounting, inspect harness and connector for damage or corrosion, reseat and retest
174-0Fuel temperature sensor reading above normal range - fuel running hotRestricted fuel return line, high ambient/engine bay heat soak, or a drifting fuel temperature sensorCheck fuel return routing for restriction, allow cool-down and recheck, then verify sensor reading against a known-good reference
262-35-volt sensor supply voltage above normal range - open circuit or short to a higher voltage source on a shared sensor supplyChafed harness shorting the sensor supply wire, corroded connector pin, or an internal ECM supply faultInspect harness and connectors feeding the affected sensors for shorts or damage before replacing components
1-5Cylinder #1 injector solenoid current below normal - open circuit on the injector solenoidBroken or disconnected injector wiring, failed injector solenoid, or a bad ECM driver circuitCheck injector wiring continuity and connector condition, swap injector connector to confirm, then test the injector solenoid
168-2Electrical system voltage erratic or intermittentLoose or corroded battery terminals, failing alternator/regulator, or an intermittent ground connectionCheck battery terminals and main grounds, load-test the batteries, and check charging output at idle and at rated speed

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

345B II attachments & work tools

Buckets

General-purpose (GP) buckets for this size class run up to about 2150 mm (84.6 in) wide at roughly 3.4 m3 (4.5 yd3); heavy-duty (HD) buckets are narrower and heavier, typically 1200-1370 mm (48-54 in) wide in the 1.6-2.4 m3 (2.1-3.0 yd3) range with 4-5 teeth for tougher digging and rock work. Buckets mount pin-on through the F-linkage bucket system, with pin diameters around 100 mm at the stick side and 80 mm at the linkage side; pin-on is the standard bucket mount at this weight class, with a hydraulic coupler as an option rather than the default.

Hydraulic hammers

This size class lines up with Cat's H160/H180 breaker range, energy class roughly 8,500-12,000 ft-lb (11,500-16,300 J), built for carriers from about 32-55 t up to 40-80 t. Operating weight for this machine (roughly 44-49 t depending on undercarriage and boom/stick configuration) puts it at the top of the H160 class or the low end of H180, so exact breaker size varies by configuration and rock hardness - confirm the specific match before ordering.

Quick couplers

Hydraulic pin-grabber quick couplers on this size class use the TB-linkage family, the same linkage used by the factory ripper for this range (roughly 110 mm stick pin, 100 mm bucket-side pin). A pin-grabber coupler lets the operator swap buckets and other tools from the cab; straight pin-on mounting without a coupler is still common at this weight class when maximum bucket capacity matters more than tool-change speed.

Thumbs/grapples

Full-rotation hydraulic thumb kits are offered for this size class, typically paired with a 1370 mm (54 in) bucket and mounted pin-on alongside the stick for grabbing rock, stumps and debris. Demolition and material-handling grapples are offered through the Material Handler / UHD factory configuration of this model, which adds reinforced structure and a dedicated attachment circuit for grapples, shears and crushers - this is a special-order variant, not the standard excavator configuration.

Rippers

A single-shank ripper is available for this size class, mounted through the TB-linkage system with roughly 110 mm stick pin and 100 mm linkage pin diameter - the same linkage family used for pin-grabber couplers on this machine. It is used for breaking up hard-pack, rock, or frozen ground ahead of bucket digging.

Hydraulic kit notes

Factory systems-operation literature covers a shared auxiliary hydraulic system across the 320B through 345B Series II excavator range, separate from the main boom/stick/bucket implement hydraulics. The auxiliary flow-control option offers up to four programmable flow presets so the operator can match flow and pressure to hammers, shears, processors and brush cutters; confirm exact flow/pressure settings for a given tool against the machine's own auxiliary hydraulic documentation before hookup.

All 345B II assemblies by section

Every catalogued assembly group for the Caterpillar 345B II. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Electrical And Starting System
160-3576 Control Gp-Hydraulic Generator
09***21Rail-Mounting; (60-cm)0
10***33Kit; (Receptacle) (Includes Receptacle As)1
12***74Bushing; (3/4-14 Thd)3
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191-2971 Generator Ar-Hydraulic
19***20Enclosure Group-Generator1
19***71Generator Ar-Hydraulic1
19***31Generator Group-Hydraulic1
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188-2632 Generator Ar-Hydraulic
18***32Generator Ar-Hydraulic1
18***33Generator Ar-Hydraulic1
18***48Installation Ar-Generator1
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188-2633 Generator Ar-Hydraulic
18***33Generator Ar-Hydraulic1
18***34Generator Group-Hydraulic1
18***46Lines Group-Hydraulic1
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194-3121 Generator Ar-Hydraulic
19***71Generator Ar-Hydraulic1
19***21Generator Ar-Hydraulic1
19***22Installation Ar-Generator1
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189-2988 Generator Gp-Hydraulic
18***88Generator Group-Hydraulic1
19***28Brush4
19***34Holder-Brush2
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191-7831 Generator Gp-Hydraulic
16***83Motor Group1
16***85Valve Group; -Hydraulic Generator1
17***99Film; (Warning) (Generator Disconnect Switch)2
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188-2634 Generator Gp-Hydraulic
16***76Control Group; (Hydraulic Generator)1
16***81Mounting Group; (Motor)1
16***83Motor Group1
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153-2521 Lamp Gp-Flood
15***21Lamp Group-Flood; -Chassis, Boom-Boom, Rear1
17***93Cover1
17***17Lens As; (Floodlight)1
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205-6343 Panel Gp-Control
00***92Screw-Washer Head; (1/4-20x0.5-In)2
09***41Screw; (Machine) (M6x1thd)2
09***21Rail-Mounting; (60-cm)1
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191-7833 Wiring Gp-Generator
06***88Locknut; (1-11-1/2-Thd)2
06***08Locknut; (1-11-1/4-Thd)4
10***48Bushing2
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188-2647 Wiring Gp-Generator
06***88Locknut; (1-11-1/2-Thd)2
06***08Locknut; (1-11-1/4-Thd)2
10***48Bushing2
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190-1582 Wiring Gp-Generator
10***01Kit; (Receptacle) (12-Pin) (Includes Receptacle As & Wedge)1
10***03Kit; (Receptacle) (3-Pin) (Includes Receptacle As & Wedge)1
12***52Kit-Cap1
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Frame And Body
191-8588 Enclosure Gp-Generator
03***15Pin1
09***91Bolt; (Locking) (M12x1.75x25mm)2
13***55Bolt; (M8x1.25x8-mm)10
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190-3420 Enclosure Gp-Generator
03***15Pin1
13***55Bolt; (M8x1.25x8-mm)10
18***84Hinge1
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Hydraulic System
191-7830 Control & Mtg Gp-Joystick
08***70Sleeve16
10***01Kit; (Receptacle) (12-Pin) (Includes Receptacle As & Wedge)1
10***03Kit; (Receptacle) (3-Pin) (Includes Receptacle As & Wedge)1
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177-2543 Drive Gp-Pump
09***91Ball Bearing1
12***01Seal-O-Ring1
17***43Drive Group-Pump1
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129-7995 Drive Gp-Auxiliary Pump
09***91Ball Bearing1
12***95Drive Group-Pump1
12***97Gear1
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194-3122 Installation Ar-Generator
08***32Cap1
18***98Bar2
18***03Guard As1
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188-2648 Installation Ar-Generator
18***98Bar2
18***03Guard As1
18***51Plate1
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191-7832 Lines Gp-Hydraulic
11***49Fitting As; (Quick Disconnect)2
14***70Elbow, 90°,-8 Orb Swiv. /-8 Orfs2
14***75Elbow Group1
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194-0574 Lines Gp-Hydraulic
12***90Hose-Hydraulic; (101.2-In)0
12***32Coupling-Permanent1
12***49Coupling-Permanent1
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191-7829 Lines Gp-Hydraulic
10***18Block1
12***90Hose-Hydraulic; (101.2-In)0
12***61Coupling-Permanent1
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188-2646 Lines Gp-Hydraulic
11***49Fitting As; (Quick Disconnect)2
14***70Elbow, 90°,-8 Orb Swiv. /-8 Orfs1
14***75Elbow Group1
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179-3625 Pump Gp-Gear
13***78Seal; (112.9mm Od)1
13***21Flange As1
13***23Gear-Drive; (15-Teeth)1
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160-5885 Valve Gp-Flow Control & Relief
16***55Valve Group; (Check)1
16***56Valve-Needle; (Generator Speed)1
16***73Retainer1
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345B II serial number reference

The PIN plate on a 345B Series II is riveted to the machine frame, usually on the right-hand side near the cab or front of the upper frame — check there before assuming a stamped location elsewhere on the undercarriage. Read the first three characters of the plate as the alpha serial prefix (identifies the specific build/parts-book series), and the digits that follow as the sequential unit number within that series.

PrefixIdentifies
AGS345B L Series II (long/mass-excavation undercarriage)
ALB345B Series II and 345B L Series II (standard and long undercarriage)
AKJ345B Series II and 345B L Series II (standard and long undercarriage)
AKX345B Series II (standard undercarriage)
ALD345B Series II
AMD345B Series II and 345B L Series II (standard and long undercarriage)
AMJ345B Series II and 345B L Series II (standard and long undercarriage)
AMN345B Series II and 345B L Series II (standard and long undercarriage)
AYR345B Series II and 345B L Series II (standard and long undercarriage)
DCW345B Series II
CCC345B Series II
FEE345B Series II
DET345B Series II Material Handler (MH)
APB345B Series II Material Handler (MH)

Frequently asked questions

What engine does the Cat 345B Series II use?

Every 345B Series II runs the Cat 3176C ATAAC inline-six, a 10.3 L turbocharged-and-aftercooled diesel rated 257 kW (345 hp) gross and 239 kW (321 hp) net at the flywheel, meeting EPA Tier 2/ADEM II emissions.

What is the operating weight of the 345B Series II?

Operating weight runs roughly 44 to 49 tonnes (about 97,000 to 108,000 lb) depending on boom/stick combination and undercarriage width, with the standard long-undercarriage build near the low end and mass-excavation (LME) builds near the top.

What replaced the Cat 345B Series II?

Cat replaced the 345B Series II with the 345C L in 2005. The 345C L moved to the C13 ACERT engine for Tier 3 emissions compliance and added a new long-reach boom option while keeping a similar digging envelope.

What 345B II owners discuss

What hydraulic quirk do owners commonly report on the 345B II once the machine warms up?
A repeated complaint is one hydraulic circuit losing pressure specifically as oil temperature climbs, with pressure normal cold. That pattern points toward a relief valve drifting out of setting, a worn pump port plate or servo, or an internal leak path that only opens once oil viscosity drops with heat. On machines running attachments like shears or hammers, a warm-oil circuit going soft has also been tied to the pump's flow compensator losing calibration. Check case drain flow and pump pressure warm versus cold before replacing parts. Have your dealer verify pump and relief valve settings before any teardown.
What usually causes a total loss-of-swing complaint on this machine, and how do techs trace it?
Loss of swing traces back most often to the swing pump-and-motor pairing rather than the brake alone. Owners have found both the swing motor and its feed pump damaged together, since metal debris from one worn component contaminates the other and takes it out too. Before condemning the motor, confirm the swing brake actually releases: the brake solenoid should read voltage from the pump controller when the joystick is worked. Have your dealer verify swing brake solenoid signal and pump controller output before replacing swing components.
What engine-related quirks show up most on the 3176C in the 345B II?
The 3176C in this application has a solid reputation overall, but low fuel pressure at cranking is a recurring no-start complaint. Reported root causes include worn fuel pump check-valve plungers sticking open and killing pressure, and injectors lifting enough to bend their own hold-down bolts. Intermittent crank-no-start is just as often a starter relay, ignition switch, or corroded harness connection rather than a fuel problem, so rule out simple wiring and relay contacts before chasing the fuel system. Have your dealer verify fuel pressure at the regulator and check-valve condition before pulling injectors.
How fast does undercarriage wear on a 345B II, and what should owners watch for?
In this weight class, ground conditions drive undercarriage wear far more than hours do. Machines run in rock or abrasive material see undercarriage life fall well short of a machine that spent its life on dirt or clay, which is why used-machine buyers grade remaining undercarriage life as a percentage rather than trusting the hour meter alone. Reman undercarriage components in this size class are typically backed for roughly 4,000 hours or a few years, a rough baseline for expected life under normal duty, but actual life swings heavily with application. Inspect bushings, sprockets, and idlers for measurable wear rather than relying on hours.
What electrical or sensor fault codes come up most for the 345B II's control system?
The 345B II's electronic control reports sensor-specific codes rather than one generic warning light. Common ones include individual cylinder (fuel injection) circuit codes for open or short conditions, a throttle switch input fault, engine oil pressure sensor open, short, or calibration-required codes, and coolant temperature sensor open or short-to-ground codes. A separate governor/throttle position sensor code shows up as an erratic or incorrect signal and is commonly traced to a damaged or loose harness connector rather than a failed sensor. Have your dealer verify sensor wiring and connectors with a diagnostic scan before swapping a sensor.
Boom or stick drift developed with hours on the machine — cylinder seal or valve?
Operators report drift on this class of excavator comes from either worn cylinder piston seals bypassing internally or a leaking section in the main control valve, and the two are told apart by swapping the hose connections at the cylinder. If the drift follows the hoses to the opposite direction, the valve is the likely cause; if it stays with the same cylinder movement, the piston seal is bypassing. A sluggish drift-reduction function, where oil returns slowly from the cylinder, has separately been linked to that valve section needing attention. Internal bypass isn't visible externally, so pressure-test before committing to a reseal.
What should a buyer check before purchasing a used 345B II?
Walk the frame, boom, and stick for cracks, dents, or repaired welds, since that signals abuse rather than fair wear, and work every hinge, latch, and pin for play. Grade the undercarriage separately from the hour meter, as a percentage of wear life remaining, because ground conditions swing wear rate significantly on this size machine. Cycle every hydraulic function under load and watch for cylinder drift or a circuit that goes soft specifically once the oil is hot, a pattern owners flag as a known warm-oil symptom on this model. Pull active and stored fault codes with a diagnostic tool instead of trusting a clean dash, since sensor and wiring faults on this control system are common and cheap to check up front. Have your dealer or an independent inspector run a full pre-purchase hydraulic and undercarriage inspection before making an offer.

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

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