Caterpillarexcavator

Caterpillar E120

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar E120 is a compact-to-mid-size hydraulic excavator built only from 1987 to 1989, exclusively in Japan under the Caterpillar-Mitsubishi joint venture. Every E120 carries the same powertrain across its short production run: a naturally aspirated, mechanically governed Mitsubishi 6D14 inline-six diesel with no electronic engine controls, rated at roughly 62.6 kW (84 hp) gross. Operating weight runs around 12,156 kg (26,800 lb), and the machine measures roughly 7.65 m long by 2.49 m wide by 2.77 m tall in standard transport trim. Caterpillar built the E120 with mechanical pilot controls and variable-flow hydraulics as the standard configuration; there was no electronic monitoring package and no documented long-reach or demolition variant. Roughly 18,600 units left the factory under the 1LF and 1MF serial prefixes before Caterpillar replaced the model with the larger E120B starting in 1989.

The E120 is essentially a badge-engineered twin of the Mitsubishi MS120, built on the same Japan platform and sharing the same engine, undercarriage, and hydraulic architecture, so service literature and many parts cross over between the two nameplates. Its successor, the E120B, is a distinct and heavier machine (around 12,927 kg / 28,500 lb operating weight) built around a different, more powerful engine package than the E120's naturally aspirated 6D14; the two models should not be treated as interchangeable for parts, engines, or manuals. In today's used and parts market, the E120 survives as a low-cost utility digger valued precisely because it has nothing electronic to fail: no ECM, no wiring-harness fault codes, and few sensors to chase. The tradeoff is age. Analog gauges, wiring, seals, and rubber hoses are all past their design life on any surviving unit, and parts support leans on the shared Mitsubishi MS120 supply chain and dismantled-machine sources rather than an active factory parts counter.

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 E120 specifications

Engine

Engine model	Mitsubishi 6D14 inline six-cylinder diesel, naturally aspirated. Fitted to 1LF-prefix production; engine fitment for the earlier 1MF-prefix run is not separately documented.
Cylinders	6, inline arrangement.
Gross power	62.6 kW (84 hp) gross, per factory-era rating for this model. Net power is not documented.
Displacement	Not documented for this application. The 6D14 block was built in several bore/stroke and boost tunes across trucks, buses, generators and construction equipment, so a single displacement figure cannot be assigned to this excavator without confirmation.
Emissions tier	None. This is a 1987 model year machine, predating U.S. EPA nonroad and EU Stage emissions regulation.

Weights

Operating weight (standard)	12,156 kg (26,800 lb) for the base 1987 configuration.
Configuration note	This figure applies to the original E120 (1LF/1MF serial prefixes) only. Closely numbered later trims carry different operating weights and are not interchangeable with this figure.
Ground pressure	Not documented for this configuration.
Transport weight	Not separately documented; treat as equal to operating weight absent a confirmed transport spec.

Dimensions

Transport length (standard)	7.65 m (25 ft 1 in).
Transport width (standard)	2.49 m (8 ft 2 in).
Transport height (standard)	2.77 m (9 ft 1 in).
Tail swing radius	Not documented for this configuration.
Track shoe width	Not documented for this configuration.
Ground clearance / undercarriage length	Not documented for this configuration.

Performance

Dig depth, reach, dump height, swing speed, travel speed, gradeability

Not documented in available literature for the original 1987 configuration. Figures published for later, closely numbered variants use a different engine and are not valid substitutes for this model.

Forces

Bucket and stick/arm digging force

Not documented in available literature for this configuration.

Service capacities (summary)

Fuel tank, hydraulic system, engine oil, cooling system

Not documented in available literature for this configuration. Verify with a dealer against the specific serial number before servicing.

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

E120 fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	Not published in any available specification source for the bare E120 (1987-1989, Japan-built, pre-dates the E120B). Two engine options were fitted across the production run depending on serial-number era; confirm exact refill volume against the machine's own O&M manual or a Cat dealer using its serial number.	Cat-era diesel engine oil to API CD/CE-class multigrade (Cat DEO-class). Era practice for this engine family: 15W-40 for general service, 10W or 10W-30 below 0 C (32 F), single-grade 30 in sustained heat above 30 C (86 F). Confirm against the viscosity-by-climate chart in the OMM for the exact engine fitted.
Cooling system	Not published for this pre-1989 configuration in available sources. Capacity depends on which engine is fitted; verify against the O&M manual or dealer records for the specific serial number.	Cat-spec heavy-duty antifreeze/coolant (extended-life or conventional, ELC-class or equivalent), mixed to a 50/50 water ratio for standard climates. Adjust concentration per the freeze-protection table in the OMM for colder regions.
Fuel tank	Not published for the bare E120 in available specification sources. Confirm exact volume against the OMM or dealer records for the specific serial number.	No. 2-D diesel fuel per standard diesel fuel spec of the era. Low-sulfur, cold-flow-treated fuel recommended in cold climates to limit gelling and filter plugging.
Hydraulic system total	Not documented for this vintage/serial range in available sources.	Cat-spec anti-wear hydraulic oil (era equivalent of Cat's HYDO/TDTO-class fluid), viscosity graded to ambient temperature per the OMM chart. Typical grade classes for this machine size are ISO 46 or 68 for temperate climates, with a lighter grade specified for cold-start regions.
Hydraulic tank	Not documented for this vintage/serial range in available sources; tank volume is a subset of the total system figure above and was not separately published.	Same hydraulic oil as the hydraulic system total, filled to the sight-gauge mark with the cylinders retracted per the OMM procedure.
Final drive (each side)	Not documented for this vintage/serial range in available sources.	Cat-spec gear/final-drive oil (TDTO-class), viscosity selected per the ambient-temperature chart in the OMM. Typical era guidance runs SAE 30 in warm climates, 10W in cold climates.
Swing drive	Not documented for this vintage/serial range in available sources.	Same TDTO-class gear oil family as the final drives, graded per the OMM ambient-temperature chart.
Grease (spec only)	Not a fill capacity; serviced per lubrication interval at each grease point rather than a bulk fill.	Cat-spec multipurpose extreme-pressure chassis grease, NLGI 2, or an equivalent EP grease, applied to boom, stick, bucket linkage, and swing-bearing points per the OMM lubrication chart.

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

Caterpillar E120 maintenance schedule

Service interval	Tasks
Every 10 h	Check engine oil, coolant, and hydraulic oil levels before starting each shift; top off as needed. Drain water and sediment from the fuel/water separator daily. Inspect for fuel, oil, and hydraulic leaks around the engine, hoses, and center swivel joint. Weekly (every 50 hours), grease all boom, stick, bucket, and swing/center swivel joint pins. Weekly, check track tension and inspect the undercarriage for loose bolts, worn pads, or damaged shoes. Weekly, check battery electrolyte level and clean terminals, since there is no electronic charge-fault warning on this machine.
Every 250 h	Change engine oil and filter. Replace the fuel filter element and bleed air from the mechanical injection system. Service the air cleaner element; clean or replace it if the restriction indicator shows red. Check alternator and fan belt tension and condition; adjust or replace as needed. Inspect wiring and gauge sender connections for corrosion, since there is no fault-code system to flag a failing sensor.
Every 500 h	Change the hydraulic return filter element. Check final drive and swing drive gear oil level; top off with the specified gear oil. Test coolant condition and corrosion-inhibitor concentration; add inhibitor as needed. Inspect and torque track shoe bolts and idler/roller mounting hardware. Check the center swivel joint for external seepage and replace seals if leaking.
Every 1,000 h	Adjust intake and exhaust valve lash on the 6D14 to the factory cold-engine clearance. Pull the injectors and injection pump for bench calibration if power or idle quality has dropped. Change hydraulic tank oil and clean the suction strainer. Check swing bearing bolt torque and inspect for bearing play. Inspect travel motors and final drives for internal leakage or unusual noise.
Every 2,000 h	Flush the hydraulic tank and replace all hydraulic filters. Pressure-test the main hydraulic pump and control valve bank for internal wear. Re-verify injection pump static timing against the factory timing marks. Inspect engine and cab mounts/isolators and replace any that are worn or hardened. Inspect final drive and swing drive gear sets for measurable wear; overhaul or replace as needed.
Every 4,000 h	Evaluate the 6D14 for a top-end or full overhaul based on a compression test and bore/liner wear check. Rebuild or replace the center swivel joint as preventive maintenance on high-hour, high-age units. Replace rubber hydraulic and fuel hoses as a precaution regardless of visible condition, given the machine's age. Re-torque and inspect the full undercarriage — track chains, sprockets, and idlers — for replacement.

Servicing the E120 beyond the schedule

Predictive Maintenance & Fluid Analysis

The 6D14 has no ECM, so there's no fault code to catch a developing problem — oil sampling is your early-warning system. Send used engine oil out every service interval to track iron and copper trends from the naturally aspirated six's bearings and liners before a bottom-end failure. Watch hydraulic oil for water intrusion around the center swivel joint seals, a known wear point on this Japan-built platform. Test coolant inhibitor levels regularly; corrosion, not electronics, is what takes this machine down.

Corrective & Common Repairs

Expect analog gauge and wiring failures before engine failures — cracked insulation and corroded grounds are common on 1980s Cat/Mitsubishi wiring looms and are usually misdiagnosed as charging or sender problems. Weak or drifting cylinders on the boom and stick point to a tired relief valve or worn spool in the control valve bank, not the pump. Travel that feels weak or one-sided is often the center swivel joint leaking internally rather than the travel motor itself — check the joint before condemning a motor.

Overhaul & Rebuild Points

At high hours, the 6D14's mechanical injection pump and injectors need bench calibration to hold power and smooth idle — pull and test them rather than guessing at timing. Swing bearing bolt torque and bearing play deserve a hard look on any machine this age; the bolts loosen and the race wears with decades of use. The center swivel joint is the E120's signature rebuild item — reseal or replace it before it contaminates the travel circuit. Final drive gear sets should be checked for backlash at overhaul.

Seasonal & Environment Servicing

Cold starts are the E120's known weak point. This naturally aspirated, mechanically governed diesel has no electronic cold-start assist, so operators often reach for an ether-assist can in freezing weather — use it sparingly, since overuse damages ring lands and bearings. Warm the block and battery first where possible. In hot, dusty applications, check the air cleaner restriction indicator more often than the factory interval suggests. Before winter layup, drain the fuel/water separator, refresh the coolant inhibitor, and grease the swivel joint and all pins.

E120 fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
No CID/FMI or SPN/FMI diagnostic codes (pre-electronic engine)	The E120 (1LF-prefix, built 1987-1989) uses a mechanically governed Mitsubishi 6D14 inline-six with jerk-pump injection and carries no engine control module, so it cannot generate Caterpillar CID/FMI or J1939 SPN/FMI trouble codes.	The machine predates Caterpillar electronic monitoring; that arrived later with the 3114-powered E120B successor, which is a different machine and engine.	Diagnose with direct mechanical and electrical checks (pressure gauges, multimeter, sender continuity) rather than a code reader; there is no diagnostic connector to plug a scan tool into.
Engine oil pressure lamp / gauge (low reading)	Warns that engine oil pressure has fallen below the safe minimum for the 6D14.	Low oil level, clogged oil filter, worn oil pump, or a failed pressure sender/switch.	Shut the engine down at once, check oil level and filter condition, and verify the sender before restarting.
Coolant temperature gauge (high reading)	Shows engine coolant temperature has risen into the overheat range.	Low coolant level, blocked radiator core, slipping or broken fan belt, or a stuck thermostat.	Reduce load, idle down, shut off once safe, let the engine cool, then check coolant level, belt, and radiator fins.
Charge / alternator warning lamp	Indicates the alternator is not charging the battery circuit.	Broken or slipping drive belt, failed alternator, or a loose or corroded wiring connection.	Check belt tension and wiring at the alternator; repair or replace before continued operation.
Air cleaner restriction indicator	Signals the air filter element is loaded enough to restrict intake airflow.	Dusty operating conditions, a worn element, or damaged intake seals.	Service or replace the air filter element and reset the restriction indicator.
Hydraulic oil temperature gauge (high reading)	Shows hydraulic fluid temperature above normal operating range.	Low hydraulic fluid level, clogged oil cooler fins, a relief valve stuck open, or sustained high-load work.	Reduce load and idle to cool the system, then check fluid level and clean the cooler fins.
Glow plug / cold-start preheat lamp	Shows the intake air preheat circuit is active before a cold start.	Normal cold-start cycle; a lamp that stays on continuously points to a stuck relay or preheat circuit fault.	Wait for the lamp to go out before cranking; if it will not go out, check the preheat relay and wiring.

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

E120 attachments & work tools

Buckets

The E120 sits in the roughly 12-tonne (26,800 lb) size class shared with the E110B/E120B and 311/312 family, and pin-on general-purpose and heavy-duty buckets for this class run about 600-1200mm (24-48 in) wide, with capacity in the 0.3-0.8 m3 (0.4-1.0 yd3) range depending on GP vs HD profile and tooth setup - varies by configuration/series. Bucket-end linkage for this class uses a 65mm (2.6 in) diameter pin about 410mm (16 in) long; confirm the exact bore on your machine before ordering, since dedicated documentation for the bare E120 (versus the better-documented E120B/311/312 siblings) is thin.

Hydraulic hammers

This 12-tonne carrier weight lines up with Cat's H110-class breaker, rated for an 8,000-14,000 kg (17,600-30,800 lb) carrier range, about 720 kg (1,588 lb) service weight, and an impact energy class near 2,034 J (1,500 ft-lbf) at 430-1,300 blows per minute. That puts the E120 toward the light end of that carrier band, so a smaller breaker in the same class line is the safer pick if the machine's actual hydraulic output runs low.

Quick couplers

Manual (pin-grabber/wedge-type) mechanical quick couplers are cataloged for the E120 in the same fitment group as the 311, 312, E110, E140 and other 12-14 tonne class machines of this era. Hydraulic (powered) couplers are not commonly cataloged for this vintage size class; a mechanical wedge-lock coupler is the typical fitment, and many E120 units in the field still run pin-on tools with no coupler at all.

Thumbs/grapples

Pin-on and weld-on hydraulic thumbs built for the shared 311/312/313/314 size class run about 600-660mm (24-26 in) wide with 3-4 tine layouts, and this same digging-end size class covers the E120. Orange-peel grapples sized for the 10-16 tonne range (also spanning 311/312/314) fit this class for scrap, brush and demolition handling; verify mounting bracket and pin spacing against the E120's actual stick end before ordering, as pin bosses can vary by production run.

Rippers

Single-shank rippers are cataloged for the shared 311/312/313/314/E-series fitment group, pin-mounted with a 65mm (2.6 in) pin diameter matching the bucket-linkage pin size for this class. These are sized for light ripping of frozen ground or soft rock rather than heavy quarry ripping, consistent with the E120's engine and hydraulic output at this weight class.

Hydraulic-kit notes

A single auxiliary function (hammer, thumb, or ripper) in this size class generally needs flow around 60-120 L/min (16-32 gpm) at roughly 14,500 kPa (2,100 psi) to run a class-matched breaker. Confirm the E120's factory or retrofitted auxiliary plumbing and relief-valve setting before adding a hammer, since not every unit of this vintage left the factory with a dedicated hammer circuit; a grapple with rotation needs a second, dual auxiliary line rather than the single line that serves a hammer or thumb.

All E120 assemblies by section

Every catalogued assembly group for the Caterpillar E120. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Engine

Alternator

Alternator General

Automatic Timer

Breather And Oil Filter

Camshaft

Connecting Rod And Bearing - Part 1 Of 2

Connecting Rod And Bearing - Part 2 Of 2

Crankshaft And Pulley

Crankshaft Bearing

Cylinder Block Part 2 Of 2

Cylinder Block Part 1 Of 2

Cylinder Block Part 1a Of 2

Cylinder Block Repair Kit - Part 1 Of 1

Cylinder Head Part 1 Of 2

Cylinder Head - Part 2 Of 2

Cylinder Head Repair Kit

Engine Attaching Parts

Engine Gasket Kit - Part 2 Of 2

Engine Gasket Kit Part 1 Of 2

Engine Hanger

Exhaust Manifold

Exhaust Muffler

Exhaust Pipe

Fan And Pulley

Flywheel

Flywheel Housing Part 1 Of 2

Flywheel Housing - Part 2 Of 2

Fuel Feed Pump

Fuel Filter - Part 1 Of 1

Fuel Hose

Fuel Injection Nozzle

Fuel Injection Pipe

Fuel Injection Pump General

Fuel Return System

Governor - Part 2 Of 5

Governor Part 3 Of 5

Governor - Part 4 Of 5

Governor - Part 1 Of 5

Governor - Part 5 Of 5

Injection Pump - Part 2 Of 2

Injection Pump - Part 1 Of 2

Inlet Manifold

Instrument (Safety Relay)

Liner And Piston Kit

Name Plate

Oil Cooler

Oil Filter

Oil Filter And Oil Level Gauge

Oil Line

Oil Pan

Oil Pump And Gear Train

Oil Strainer

Piston

Rocker Cover

Starter Part 1 Of 2

Starter - Part 2 Of 2

Starter General

Timing Gear - Part 1 Of 2

Timing Gear - Part 2 Of 2

Valve Gear Train - Part 2 Of 2

Valve Gear Train (Continued) - Part 1 Of 2

Water Pipe And Thermostat

Water Pump

Water Temp Gauge Unit

Vehicle

Accumulator (1lf1-09264)

Adjuster Cylinder

Air Cleaner

Air Conditioner Part 2 Of 3

Air Conditioner Part 1 Of 3

Air Conditioner - Part 3 Of 3

Air Conditioner Compressor

Air Conditioner Condenser And Receiver

Air Conditioner Harness

Air Conditioner Lines

Am/Fm Radio (1lf1-09251 Std 1lf09252- O.P.)

Arm And Bucket Lines Part 1 Of 2

Arm And Bucket Lines - Part 2 Of 2

Arm Cylinder (For Telescopic Arm) - Part 2 Of 2

Arm Cylinder - Part 2 Of 2

Arm Cylinder Part 1 Of 2

Arm Cylinder (For Telescopic Arm) Part 1 Of 2

Arm Lines (For Breaker/Double Acting Actuators)

Auto Lock (1lf-09263)

Bank Forming Bucket

Base Frame

Boom And Accessories - Part 2 Of 2

Boom And Accessories Part 1 Of 2

Boom And Accessories (For Breaker/Double Acting Actuators) - Part 1 Of 2

Boom And Accessories (For Breaker/Double Acting Actuators) - Part 2 Of 2

Boom Cylinder Part 1 Of 2

Boom Cylinder - Part 2 Of 2

Boom Light And Harness

Boom Lines

Boom Lines (For Breaker/Double Acting Actuators)

Bucket - Sae 5/8 Cubic Yards (Jis 0.45 Cubic Meters)

Bucket - Sae 5/8 Cubic Yards (Jis 0.5 Cubic Meters)

Bucket - Sae 1/2 Cubic Yards (Jis 0.35 Cubic Meters)

Bucket - Sae 1/4 Cubic Yards (Jis 0.22 Cubic Meters)

Bucket - Sae 1/4 Cubic Yards (Jis 0.15 Cubic Meters)

Bucket - Sae 3/4 Cubic Yards (Jis 0.55 Cubic Meters)

Bucket Cylinder - Part 2 Of 2

Bucket Cylinder Part 1 Of 2

Bucket With Ejector - Sae 1/4 Cubic Yards (Jis 0.21 Cubic Meters)

Cab (Door And Window Frame) Part 2c Of 4

Cab (Door And Window Frame) Part 2 Of 4

Cab (Frame) Part 1e Of 4

Cab (Interior Parts)-Part 4 Of 4

Cab (Door And Window Frame) Part 2b Of 4

Cab (Door And Window Frame) Part 2d Of 4

Cab (Frame) Part 1 Of 4

Cab (Frame) Part 1c Of 4

Cab (Frame) Part 1a Of 4

Cab (Glass And Corner Rubber) Part 3 Of 4

Cab (Interior Parts)-Part 4a Of 4

Cab (Frame) Part 1d Of 4

Cab (Window Washer)-Part 4b Of 4

Cab (Frame) - Part 1b Of 4

Cab (Door And Window Frame) Part 2a Of 4

Cab Heater-Part 2 Of 2

Cab Heater-Part 1 Of 2

Carrier Roller

Control Valve A Part 2 Of 4

Control Valve A Part 3 Of 4

Control Valve A - Part 4 Of 4

Control Valve A Part 1 Of 4

Control Valve B Part 2 Of 4

Control Valve B Part 3 Of 4

Control Valve B - Part 1 Of 4

Control Valve B - Part 4 Of 4

Controls (For 2 Pumps - Double Acting Actuators)

Controls (For 1 Pump - Breaker/Double Acting Actuators)

Controls (For Telescopic Arm)

Cross Over Relief Valve - Part 2 Of 2

Cross Over Relief Valve Part 1 Of 2

Delivery Lines

Drain Lines Part 1 Of 2

Drain Lines (For Swing Parking Brake) - Part 2 Of 2

Drain Lines (For Swing Parking Brake) Part 1 Of 2

Drain Lines - Part 2 Of 2

Electric Parts (For Cold Weather)

Electric Parts Part 1 Of 2

Electric Parts - Part 2 Of 2

Engine - Part 2a Of 2

Engine Part 2 Of 2

Engine Part 1 Of 2

Engine Control (For Automatic Engine Speed Control)-Part 3 Of 3

Engine Control (For Automatic Engine Speed Control) Part 2 Of 3

Engine Control (For Automatic Engine Speed Control) - Part 1 Of 3

Engine Control

Engine Hood Part 1 Of 2

Engine Hood-Part 2 Of 2

Floor Mat (For Breaker/Double Acting Actuators)

Front Guard

Front Lines (For Telescopic Arm)-Part 2 Of 2

Front Lines (For Swing Parking Brake)

Front Lines (For Telescopic Arm)-Part 1 Of 2

Front Lines

Front Lubrication Lines

Front Pilot Lines (For Breaker)

Fuel Tank And Fuel Lines - Part 2 Of 2

Fuel Tank And Fuel Lines - Part 1 Of 2

Gear Pump

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) (For Telescopic Arm) Part 2 Of 3

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) - Part 5 Of 5

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) (For Telescopic Arm) - Part 3 Of 3

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) (For Telescopic Arm) Part 1 Of 3

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) Part 2 Of 5

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) Part 4 Of 5

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) - Part 1 Of 5

Grab Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters) Part 3 Of 5

Grab Bucket Cylinder Part 1 Of 2

Grab Bucket Cylinder - Part 2 Of 2

Grapple

Grease Bath

Head Guard

Head Rest

Hydraulic Tank - Part 2 Of 2

Hydraulic Tank (For Cold Weather) Part 1 Of 2

Hydraulic Tank (For Cold Weather) - Part 2 Of 2

Hydraulic Tank Part 1 Of 2

Idler Wheel

Link And Rod

Long Arm - 9'8" (2940mm) - Part 2 Of 2

Long Arm - 9'8" (2940mm) Part 1 Of 2

Long Arm - 9'8" (2940mm) (For Breaker/Double Acting Actuators) - Part 2 Of 2

Long Arm - 9'8" (2940mm) (For Breaker/Double Acting Actuators) - Part 1 Of 2

Lower Structure Cover

Medium Arm - 8' (2440mm) - Part 2 Of 2

Medium Arm - 8' (2440mm) (For Breaker/Double Acting Actuators) - Part 2 Of 2

Medium Arm - 8' (2440mm) (For Breaker/Double Acting Actuators) - Part 1 Of 2

Medium Arm - 8' (2440mm) Part 1 Of 2

Name Plate And Label (For Cold Weather)

Name Plate And Label (For Automatic Engine Speed Control)

Name Plate And Label (For Telescopic Arm)

Name Plate And Label (For Breaker)

Name Plate And Label (Cab)

Name Plate And Label (Body)

Nipper - Part 2 Of 2

Nipper - Part 1 Of 2

Over Load Relief Valve (For Telescopic Arm)

P.T.O. Valve (For Telescopic Arm) Part 1 Of 2

P.T.O. Valve (For Telescopic Arm) - Part 2 Of 2

P.T.O. Valve (For 2 Pumps - Double Acting Actuators)

Pilot Filter

Pump Part 5 Of 11

Pump Part 10 Of 11

Pump Part 8 Of 11

Pump Part 1 Of 11

Pump Part 3 Of 11

Pump - Part 11 Of 11

Pump Part 9 Of 11

Pump Part 6 Of 11

Pump Part 2 Of 11

Pump Part 7 Of 11

Pump Part 4 Of 11

Pump Drive

Pump Suction Lines

Radiator - Part 3 Of 3

Radiator - Part 2 Of 3

Radiator (For Air Conditioner) Part 2 Of 3

Radiator (For Air Conditioner) - Part 3 Of 3

Radiator - Part 1 Of 3

Radiator (For Air Conditioner) Part 1 Of 3

Radiator Baffle Plate

Radio Mantle (1lf1-09251 O.P. 1lf09252- Std)

Relay Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 1 Of 2

Relay Box (For Automatic Engine Speed Control And Swing Parking Brake)-Part 2 Of 2

Relay Box

Relief Valve (1lf1-09264)

Relief Valve (For Breaker/Double Acting Actuators)

Relief Valve (1lf09265-)

Remote Control Valve - Part 2 Of 2

Remote Control Valve (For Automatic Engine Speed Control) Part 1 Of 3

Remote Control Valve Part 1 Of 2

Remote Control Valve (For Automatic Engine Speed Control) - Part 3 Of 3

Remote Control Valve (For Telescopic Arm) - Part 1 Of 2

Remote Control Valve (For Telescopic Arm) - Part 2 Of 2

Remote Control Valve (For Automatic Engine Speed Control) Part 2 Of 3

Return Lines - Part 2 Of 2

Return Lines (For Swing Parking Brake) Part 1 Of 2

Return Lines (For Swing Parking Brake) - Part 2 Of 2

Return Lines - Part 1 Of 2

Ripper

Rotary Joint

Seat And Floor Mat-Part 2 Of 3

Seat And Floor Mat-Part 1 Of 3

Seat And Floor Mat-Part 3 Of 3

Seat Belt

Servo And Pilot Lines (For Automatic Engine Speed Control) - Part 2 Of 2

Servo And Pilot Lines (For Automatic Engine Speed Control And Swing Parking Brake) - Part 2 Of 2

Servo And Pilot Lines (1lf09265-) Part 4 Of 4

Servo And Pilot Lines (For Automatic Engine Speed Control) - Part 1 Of 2

Servo And Pilot Lines - Part 1 Of 4

Servo And Pilot Lines (1lf09265-) Part 4a Of 4

Servo And Pilot Lines (For Swing Parking Brake) - Part 2 Of 2

Servo And Pilot Lines (For Telescopic Arm)

Servo And Pilot Lines (1lf1-09264) Part 3a Of 4

Servo And Pilot Lines Part 2a Of 4

Servo And Pilot Lines Part 2 Of 4

Servo And Pilot Lines Part 1a Of 4

Servo And Pilot Lines (For Swing Parking Brake) - Part 1 Of 2

Servo And Pilot Lines (1lf1-09264) Part 3 Of 4

Servo And Pilot Lines (For Automatic Engine Speed Control And Swing Parking Brake) Part 1 Of 2

Short Arm - 6'4-3/8" (1940mm) (For Breaker/Double Acting Actuators) - Part 1 Of 2

Short Arm - 6'4-3/8" (1940mm) - Part 2 Of 2

Short Arm - 6'4-3/8" (1940mm) (For Breaker/Double Acting Actuators) - Part 2 Of 2

Short Arm - 6'4-3/8" (1940mm) Part 1 Of 2

Shut Off Valve

Shuttle Valve (For Automatic Engine Speed Control)

Side Mirror

Slow Return Valve

Solenoid Valve (For Telescopic Arm)

Solenoid Valve

Solenoid Valve (For Breaker)

Solenoid Valve (For Swing Parking Brake)

Swing Brake (For Swing Parking Brake) - Part 2 Of 2

Swing Brake (For Swing Parking Brake) Part 1 Of 2

Swing Drive - Part 1 Of 2

Swing Drive (For Swing Parking Brake)

Swing Drive - Part 2 Of 2

Swing Frame (For Breaker/Double Acting Actuators)

Swing Frame And Counter Weight (For Telescopic Arm)

Swing Frame And Counter Weight - Part 1 Of 2

Swing Frame And Counter Weight - Part 2 Of 2

Swing Frame Cover (For Breaker/Double Acting Actuators/Telescopic Arm) - Part 1 Of 3

Swing Frame Cover (Side) (For Extreme Hot Weather) Part 1 Of 2

Swing Frame Cover (For Vandalism Guard)

Swing Frame Cover (For Breaker/Double Acting Actuators/Telescopic Arm) - Part 2 Of 3

Swing Frame Cover (Under) (For Extreme Hot Weather)

Swing Frame Cover (Side) (For Extreme Hot Weather) - Part 2 Of 2

Swing Frame Cover (Side) Part 2 Of 3

Swing Frame Cover (Support)

Swing Frame Cover (For Breaker/Double Acting Actuators/Telescopic Arm) - Part 3 Of 3

Swing Frame Cover (Side) - Part 3 Of 3

Swing Frame Cover (Upper)

Swing Frame Cover (Under)

Swing Frame Cover (Side) Part 1 Of 3

Swing Gear - Part 2 Of 2

Swing Gear Part 1 Of 2

Swing Lines

Swing Lines (For Swing Parking Brake)

Swing Motor Part 2 Of 3

Swing Motor Part 1 Of 3

Swing Motor - Part 3 Of 3

Switch And Harness (For Breaker)

Switch Box (Body) - Part 3b Of 3

Switch Box (Body) Part 3 Of 3

Switch Box (Panel) Part 1a Of 3

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 3 Of 6

Switch Box (For Telescopic Arm)

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 5 Of 6

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 1 Of 6

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 4 Of 6

Switch Box (Panel) Part 1 Of 3

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) Part 2 Of 6

Switch Box (Body) Part 3a Of 3

Switch Box (Meter Unit) Part 2 Of 3

Switch Box (For Automatic Engine Speed Control And Swing Parking Brake) - Part 6 Of 6

Telescopic Arm Part 1 Of 2

Telescopic Arm - Part 2 Of 2

Telescopic Lines-Part 1 Of 2

Telescopic Lines-Part 2 Of 2

Tool And Battery Box

Track 19-5/8"(500mm) Triple Grouser Shoes

Track 19-5/8" (500mm) Flat Shoes

Track 23-5/8" (600mm) Triple Grouser Shoes

Track 27-1/2" (700mm) Triple Grouser Shoes

Track 30-3/8" (770mm) Triangle Shoes

Track 30-3/8" (770mm) Triple Grouser Shoes

Track Roller

Trapezoidal Bucket - Sae 3/8 Cubic Yards (Jis 0.3 Cubic Meters)

Travel Drive - Part 5 Of 5

Travel Drive Part 2 Of 5

Travel Drive Part 1 Of 5

Travel Drive Part 4 Of 5

Travel Drive Part 3 Of 5

Travel Drive And Sprocket

Travel Lines - Part 2 Of 2

Travel Lines Part 1 Of 2

Travel Motor Lines Part 1 Of 2

Travel Motor Lines - Part 2 Of 2

Traveling Control (For Automatic Engine Speed Control) (1lf1-09264)-Part 1 Of 2

Traveling Control - Part 1 Of 2

Traveling Control (For Automatic Engine Speed Control) (1lf1-09264)-Part 2 Of 2

Traveling Control (For Automatic Engine Speed Control) (1lf09265-)-Part 2 Of 3

Traveling Control (For Automatic Engine Speed Control) (1lf09265-)-Part 3 Of 3

Traveling Control (For Automatic Engine Speed Control) (1lf09265-)-Part 1 Of 3

Traveling Control - Part 2 Of 2

Upper Structure Lines (For Telescopic Arm) - Part 2 Of 2

Upper Structure Lines (For Telescopic Arm) - Part 1 Of 2

Upper Structure Lines (For 1 Pump - Double Acting Actuators)

Upper Structure Lines (For 2 Pumps Combined Flow - Double Acting Actuators) - Part 2 Of 2

Upper Structure Lines (For Telescopic Arm) - Part 1a Of 2

Upper Structure Lines (For 2 Pumps Combined Flow - Double Acting Actuators) - Part 1 Of 2

Upper Structure Lines (For 1 Pump - Breaker)

Upper Structure Lines (For Telescopic Arm)-Part 2a Of 2

Vandalism Guard

Wiper Motor

Wiring Harness Part 1 Of 2

Wiring Harness (For Cold Weather) - Part 2 Of 2

Wiring Harness - Part 2 Of 2

Wiring Harness (For Cold Weather) - Part 1 Of 2

Working Control - Part 1 Of 2

Working Control (For Automatic Engine Speed Control)

Working Control - Part 2 Of 2

Yoke And Tension

E120 serial number reference

On an E120 the PIN plate is a riveted metal tag on the upper structure, typically front-right near the cab or boom foot pivot. If the tag is missing or unreadable, the number is also stamped into the frame itself nearby. The first three characters of the PIN are the prefix - it identifies the model and production run - and the digits after it are the machine's sequential build number within that run.

Prefix	Identifies	Notes
1LF	E120 (original, pre-B generation), Japan-built	Production ran 1987 into 1989, ahead of the E120B changeover. Fitted with the Mitsubishi 6D14 diesel. No documented hardware split (undercarriage length, arm, etc.) versus 1MF-prefix units - if that matters for parts fitment, confirm with your dealer.
1MF	E120 (original, pre-B generation), Japan-built	Production ran 1987 into 1988, the same launch window as 1LF and ending a year earlier. Appears to be a parallel serial block of the same base E120 rather than a separate hardware variant. The Mitsubishi 6D14 engine tie is documented for 1LF-prefix units; not separately documented for 1MF - confirm with your dealer before assuming an exact match.

Frequently asked questions

What engine does the Caterpillar E120 use?

Every Caterpillar E120 is powered by the naturally aspirated, mechanically governed Mitsubishi 6D14 inline-six diesel, rated at roughly 62.6 kW (84 hp) gross. There is no ECM or electronic fuel system on this engine; fueling is handled entirely by a mechanical injection pump and governor.

What is the operating weight of the Caterpillar E120?

The E120's operating weight runs around 12,156 kg (26,800 lb), varying slightly with undercarriage and bucket configuration. Standard transport dimensions are roughly 7.65 m long, 2.49 m wide, and 2.77 m tall.

What replaced the Caterpillar E120?

Caterpillar replaced the E120 with the E120B starting in 1989. The E120B is a larger, heavier machine, around 12,927 kg (28,500 lb) operating weight, built around a different and more powerful engine package than the original E120's naturally aspirated 6D14 — treat the two models as separate machines for parts and service purposes.

What E120 owners discuss

What's the real-world experience with the E120's engine? Any known quirks?

The E120 runs a naturally aspirated Mitsubishi 6D14 inline-six with a mechanical (jerk-pump) injection system — no electronic engine controls on this generation. Owners of mechanical-injection diesels this age consistently report the same failure signature: a hard cold start, uneven idle, or a puff of white or blue smoke on startup usually traces back to a tired injection pump, worn injectors, or a weak battery bank rather than anything electronic. Compression loss from decades of hours is the other usual suspect behind a no-start. Starting fluid can mask a weak-cranking problem for a while, but repeated use washes oil off the cylinder walls and accelerates wear, so it gets treated as a last resort, not a routine fix. Have a diesel tech check cranking speed, compression, and injection timing before relying on starting fluid as a regular cold-start aid.

Why does the hydraulic system feel sluggish or noisy under load?

This generation uses variable-displacement piston pumps paired with mechanical, lever-and-linkage implement controls — there's no electronic flow-sharing or load-sensing computer to blame. A whining or rising-pitch pump noise under load almost always points to cavitation: low reservoir level, a clogged suction strainer, or oil too cold or too viscous to draw in freely. A hissing or whistling sound paired with lost lifting or digging power under load points to the main relief valve holding pressure incorrectly rather than a pump on its way out. Because everything routes through mechanical linkage, a sticky or misadjusted control rod can mimic a hydraulic fault, so linkage wear gets ruled out first before anyone tears into the pump.

What undercarriage wear should an owner expect on a machine this size and age?

For an excavator in this operating-weight class (roughly 12 tonnes / 26,500 lb), track sag past about 25-40 mm (1-1.5 in) beyond factory tension spec is the usual trigger point owners use to call for adjustment or replacement. Rollers, idlers, and sprockets wear fastest on machines that spend more time traveling than digging, and uneven side-to-side wear usually means one track or final drive has been running out of adjustment for a while rather than pointing to a manufacturing issue. On a machine of this vintage, expect the undercarriage — not the upperstructure — to be the biggest line item in a pre-purchase repair estimate.

Does the E120 share its engine with the later E120B, or any other Cat model?

No — don't cross-shop parts or specs between them. The original E120, built only in Japan and carrying 1LF or 1MF serial prefixes, uses the naturally aspirated Mitsubishi 6D14. The follow-on E120B is a different machine under the same size-class name: depending on the source, it's documented with either a Cat 3114 or a turbocharged Mitsubishi S4K, not the 6D14 — treat this as varying by configuration until a data plate confirms it. Verify which engine is actually fitted to a given machine, from the data plate and injection pump tag, before ordering rebuild kits or gaskets. 6D14 parts will not fit a 3114 or S4K-T.

What electrical or sensor problems come up on a machine this old?

This generation predates onboard diagnostics entirely — there's no ECM, no fault codes, and nothing resembling a modern sensor suite. The gauge cluster is a straightforward analog setup for charge, temperature, and oil pressure, fed by simple senders. After several decades in service, the usual complaints are corroded or high-resistance connectors, cracked wiring insulation, and a tired alternator or voltage regulator rather than any sensor failure. When a gauge reads wrong or the charge light misbehaves, checking grounds and connector pins first resolves most reported cases before anyone replaces a sender or the alternator itself.

What is the center swivel joint issue owners mention, and how does it show up?

The center swivel joint, also called the rotary manifold, sits in the middle of the undercarriage and carries hydraulic oil from the upperstructure controls down to the travel motors while the house rotates freely. Across this Japan-built Cat and Mitsubishi excavator lineage, it's a known high-hour wear item — internal seals harden and leak, letting oil bypass between the left and right travel circuits. Telltale symptoms are a machine that pulls to one side while traveling straight, noticeably weaker hill-climbing power, or hydraulic oil showing up mixed into the final drive gear oil. This isn't documented for every individual E120 serial range, but the design and the failure mode carry through the whole family, so it's worth checking on any high-hour example.

What should someone check before buying a used E120?

Confirm the data plate and injection pump match a genuine 1987-89 Japan-built machine carrying a 1LF or 1MF serial prefix with the Mitsubishi 6D14 engine — don't assume parts or specs carry over from an E120B. Rotate the house through a full swing and listen for grinding or feel for play in the swing bearing. Check final drive oil level and compare left and right travel speed side by side; a mismatch points to a worn travel motor or a leaking center swivel joint. Inspect track tension and roller, idler, and sprocket wear, since undercarriage repair is usually the biggest cost surprise on a machine this age. Look for hydraulic oil weeping from the center swivel joint and confirm the main relief valve holds pressure under a loaded test, not just at idle. Because this exact model is rare on the used market, line up a parts plan before buying — much of the driveline and undercarriage crosses to the Mitsubishi-badged sibling machine of the same size class, which can be easier to source than Cat-branded parts. Have a dealer or independent tech verify swing bearing condition and hydraulic relief pressures before putting the machine back into regular service.

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

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