Question 1

What engine does the Caterpillar 311 use?

Accepted Answer

The original 311 (1994-1997) runs the Cat 3064, a naturally aspirated, mechanically governed inline-four diesel rated about 59 kW (79 hp), with a mechanical injection pump and no engine ECM. Later 311B, 311C, and 311D LRR generations switch to turbocharged 3064T or 3054 engines with electronic governing; those are different engines, not a running change on this original model.

Question 2

What is the operating weight of the Caterpillar 311?

Accepted Answer

Operating weight is about 11.4 t (25,100 lb) in standard configuration. Used-equipment listings for this generation range from roughly 24,400 to 25,100 lb depending on the bucket and attachments fitted, so check the machine's own rating plate for its exact figure.

Question 3

What replaced the Caterpillar 311?

Accepted Answer

Caterpillar replaced the 311 with the 311B in 1997, which added a turbocharged engine and continued as the 311C and then the 311D LRR in the same size class. None of those later generations share the base 311's naturally aspirated 3064 engine or its fully mechanical fuel system.

Question 4

What engine is actually in the original Cat 311, and why do people say it's 'a Mitsubishi with a Cat badge'?

Accepted Answer

The first-generation 311 (built through the late 1990s) uses the Cat 3064, a naturally aspirated, mechanically governed inline diesel rated around 59 kW (79 hp) at the flywheel. There is no electronic engine control on this generation - injection timing and fueling are set by the mechanical pump and governor linkage, not an ECM. The 3064 comes out of the Caterpillar-Mitsubishi joint engine program, the same family that produced the 3046 and 3066, so owners often note the block and internals track closely with an industrial Mitsubishi diesel of the same displacement class. Cat-specific calibration and some bolt-on components still don't interchange straight across with a raw Mitsubishi parts book, so match components by the Cat serial and arrangement rather than assuming a one-to-one swap. A recurring complaint on this engine is a rough, uneven idle or misfire feel that clears up once a load comes on - that is usually chased to a tired injection pump, worn injectors, or a governor linkage needing adjustment, not anything electronic. Watch for later, visually similar 311B/311C/311D LRR listings that use a turbocharged 3064T or a 3054/C4.2 with electronic controls - that is a different engine generation with its own fault-code diagnostics, not what came under the hood of the original 311.

Question 5

Why does one track pull weaker than the other when traveling straight, and is that the final drive?

Accepted Answer

Owners chasing this usually find it is not the final drive gear itself. Each track has its own dedicated piston pump section and its own travel motor, so a track that stays lazier in both directions points upstream - a pump section out of calibration, a restricted pressure passage in the main control valve, or internal leakage at the center swivel (the rotating joint carrying hydraulic oil from the upper to the undercarriage) cross-porting oil between circuits. A common diagnostic step is to cross the two travel pressure lines at the control valve outlets - if the weak side follows the line swap, the fault is upstream in the valve or pump circuit, not the motor or final drive. Because this affects propel power on grade, have your dealer verify pump calibration and relief settings before relying on the machine on a slope.

Question 6

The travel motor is weeping oil right where it meets the sprocket - what's going on?

Accepted Answer

That is the classic wear point on this style of travel motor: a floating face seal, often called a duo-cone seal, between the motor housing and the sprocket hub. Once it starts to wear, motor case oil and final drive oil weep at that joint. It is a known wear item on this generation of compact excavator drive motor generally, not a sign of a bad individual unit. Because the travel motor housing also carries the spring-applied, hydraulically-released parking brake, do not let a weep go unaddressed - have your dealer verify the brake and seal condition before the machine goes back into daily grade work.

Question 7

The track adjuster keeps losing grease - is that a simple reseal?

Accepted Answer

Not a quick one on this machine. The adjuster cylinder sits behind the front idler and recoil spring assembly rather than out in the open, so a leaking adjuster seal means slacking the track, pulling the idler and recoil group, and then removing the adjuster to reseal it. While it is apart, check how much travel is left in the idler's adjustment range - if the idler is already run near the end of its travel, the adjuster cylinder can get kinked as the idler bounces on rough ground, which just repeats the same leak soon after the reseal.

Question 8

Why does the swing hesitate for a moment before it starts moving?

Accepted Answer

A short pause between moving the swing lever and the upper actually turning is normal - it is the spring-applied, hydraulically-released swing parking brake taking a moment to release, more noticeable with cold hydraulic oil. What is not normal is a hesitation that keeps growing, or swing motion continuing after the lever is centered and travel should stop. Either points to brake wear or a leaking brake-release circuit rather than a simple adjustment. Because this brake is what holds a suspended load or keeps the house from swinging on a grade, have your dealer verify the brake pack and release valve before trusting it on a slope or near the edge of an excavation.

Question 9

How do you troubleshoot a no-start or charging complaint on this machine - is there a fault code to read?

Accepted Answer

No. This generation has no onboard diagnostic display or ECM to pull codes from, so electrical troubleshooting is done with a wiring diagram and a multimeter rather than a scan tool. Recurring complaints include a starting-circuit fuse that blows on crank, usually traced to corroded or loose connections between the battery, starter solenoid, and start switch rather than the starter itself, and charging complaints that come down to alternator brushes, the regulator, or a corroded ground strap rather than any sensor. Given the machine's age, budget time for cleaning and re-terminating connectors before condemning a part.

Question 10

What should you check before buying a used original Cat 311?

Accepted Answer

First, confirm it is genuinely the earlier mechanical 311 and not a later 311B/C/D relisted under the shorter name - look for the absence of any onboard monitor or gauge-cluster fault display, and a mechanical, linkage-actuated injection pump with no ECM connector on the engine harness. If it is an import, note the serial prefix; gray-market machines can carry different cab and hydraulic components than domestic-prefix units, which affects parts lookup and manual cross-reference. On a test run: let the engine idle cold and watch for roughness that clears up under load, which points to a tired injection pump; run both tracks side by side on flat ground and compare pull; check both travel motor sprocket hubs for oil weep and both track adjusters for grease weep; and hold the swing lever centered mid-swing on a slight grade to confirm the parking brake holds without drift. Given how old these machines now are regardless of care, have your dealer or a qualified tech run a full hydraulic and brake inspection before putting it into daily work.

Engine model	Cat 3064, naturally aspirated inline-4 diesel. The later 311B/311C generations switch to the turbocharged 3064T instead.
Gross/net power	59 kW (79 hp) flywheel output.
Displacement	4.25 L (259 cu in).
Cylinders	4 cylinders in line, bore x stroke 102 x 130 mm (4.02 x 5.12 in).
Emissions tier	No emissions tier rating. Built 1994-1997, before nonroad diesel emissions standards applied to this power class.

Operating weight	11.4 t (25,100 lb) in standard configuration. Used-equipment listings for this generation show weight ranging from about 24,400 lb to 25,100 lb depending on bucket and attachments fitted.
Ground pressure	Not published for this original series with standard 500 mm (20 in) shoes. Ground-pressure figures found for later 311B/311C/311D generations do not carry over to this machine.

Transport length	7.25 m (23 ft 9 in).
Transport width	2.49 m (8 ft 2 in).
Transport height	2.76 m (9 ft 1 in).
Track shoe width	500 mm (20 in) standard triple-grouser shoe.
Tail swing radius / ground clearance / undercarriage length	Not documented for this original series. Tail swing, ground clearance, and undercarriage-length figures found online belong to the later 311B/311C/311D LRR/311F generations and should not be assumed to apply here.

Max dig depth	5.6 m (18 ft 4 in).
Max reach at ground	8.1 m (26 ft 7 in).
Max dump height / swing speed / travel speed / gradeability / drawbar pull	Not documented for this original series. Every dump-height, swing-speed, travel-speed, and gradeability figure found in research is specific to the later 311B/311C/311C Utility/311D LRR/311F generations and does not carry over.

Bucket digging force	73.55 kN (16,535 lbf) breakout force with the standard bucket.
Stick/arm digging force	Not published separately for this original series. Available factory figures for this generation list only the bucket breakout force above.

Caterpillar 311

Caterpillar 311 specifications

Engine

Weights

Dimensions

Performance

Forces

Service capacities (summary)

311 fluids & capacities

Caterpillar 311 maintenance schedule

Servicing the 311 beyond the schedule

Predictive Maintenance & Fluid Analysis

Corrective & Common Repairs

Overhaul & Rebuild Points

Seasonal & Environment Servicing

311 fault codes & troubleshooting

311 attachments & work tools

Buckets

Hydraulic hammers

Quick couplers

Thumbs/grapples

Rippers

Hydraulic-kit notes

All 311 assemblies by section

311 serial number reference

Frequently asked questions

What 311 owners discuss

Need a specific 311 part?

System	Capacity	Recommended fluid
Engine crankcase (with filter)	13 L (3.4 US gal)	Cat DEO diesel engine oil, API CD/CE multigrade. Use a lighter SAE 10W-30 for cold ambient starts and SAE 15W-40 for temperate-to-hot climates, per Cat's engine oil viscosity chart.
Cooling system	about 17 L total: 15.5 L jacket plus 1.5 L recovery bottle (4.5 US gal)	Cat DEAC (Diesel Engine Antifreeze/Coolant), the factory fill for this era. Cat ELC (Extended Life Coolant) is accepted as a longer-drain alternative on refill.
Fuel tank	reported 90-140 L (24-37 US gal) for the base 311 depending on source; treat as varies by configuration and confirm against the machine's own capacity chart. Do not confuse with the later 311C Utility's larger 195 L (51.5 US gal) tank.	No. 2-D diesel fuel, minimum cetane rating of 40. No. 1-D diesel is acceptable in cold-start conditions.
Hydraulic system total	146 L (38.6 US gal)	Cat HYDO anti-wear hydraulic oil, viscosity graded by ambient temperature: thinner grade for cold starts, heavier grade for sustained hot-climate operation.
Hydraulic tank	99 L reservoir (26 US gal)	Cat HYDO anti-wear hydraulic oil, same climate-based viscosity selection as the total hydraulic system.
Final drive (each)	2.6 L each (0.7 US gal)	Cat TDTO gear oil, TO-4 specification. SAE 30 for roughly -20 to 25 C (-4 to 77 F), SAE 40 for -10 to 40 C (14 to 104 F), SAE 50 for 0 to 50 C (32 to 122 F), selected by ambient temperature.
Swing drive	2.8 L (0.7 US gal)	Cat TDTO gear oil, TO-4 specification, same SAE 30/40/50 ambient-temperature selection as the final drives.
Pilot/other circuits	not separately listed; the pilot and servo control circuit draws from the main hydraulic reservoir	Same Cat HYDO anti-wear hydraulic oil used in the main hydraulic system.
Grease (all pin and bushing points)	spec only, no reservoir volume	Cat multipurpose EP grease, moly-fortified, NLGI 2 consistency.

Service interval	Tasks
Every 10 h	Check engine oil level and top off before starting. Check coolant level in the radiator overflow bottle. Drain water and sediment from the fuel/water separator. Walk around the machine and check for hydraulic, fuel, and oil leaks and loose fasteners. Grease boom, stick, and bucket linkage pins daily; check track tension and inspect the undercarriage for wear weekly. Confirm the oil pressure, coolant temperature, and charging warning lamps light at start-up, since this machine has no digital fault display to fall back on.
Every 250 h	Change engine oil and replace the oil filter. Replace the fuel filter element. Check final drive and swing drive gear oil levels. Clean or replace the primary air filter element. Check alternator and fan belt tension and condition. Grease the swing bearing and check swing gear backlash by hand.
Every 500 h	Take an engine oil sample for lab analysis. Change the final drive gear oil in each travel motor. Change the swing drive gear oil. Inspect the travel motor sprocket hubs for oil weep at the seal between motor and hub. Check the mechanical fuel injection pump and lines for leaks. Sample hydraulic oil for contamination and wear metals.
Every 1,000 h	Replace the hydraulic tank breather/filler element. Check and adjust engine valve lash. Inspect fuel injection pump timing and injector spray pattern. Measure track chain pitch elongation and pin/bushing wear. Check swing bearing bolt torque. Inspect the track adjuster and recoil spring assembly for grease or oil leakage.
Every 2,000 h	Change the hydraulic tank oil and clean the tank strainer. Test coolant condition and renew the fill if it is outside specification. Inspect the water pump for bearing play and seal leakage. Run a full undercarriage wear check covering chain pitch, roller and idler wear, and sprocket tooth wear. Inspect the swing and travel parking brakes for holding capacity and release-circuit leakage. Check engine and cab mounts for cracking or looseness.
Every 4,000 h	Rebuild or bench-test the mechanical fuel injection pump and injectors. Overhaul or replace track chain, rollers, idlers, and sprockets once worn past factory limits. Inspect and reseal the main hydraulic pump and cylinder rods. Perform an engine inframe inspection of liners, bearings, and rings if oil consumption or blow-by has increased. Inspect and rebuild the swing and travel brake packs and motor seals as needed.

Code	Meaning	Likely cause	What to do
No engine ECM / no CID-FMI-MID codes	The base 1994-1997 Cat 311 runs the naturally aspirated Cat 3064 (a Mitsubishi S4K-derived inline-4 diesel) with a mechanical governor and a mechanical (jerk-type) injection pump. There is no engine ECM and no electronic monitoring computer on this generation, so it never generates Caterpillar's standard MID-CID-FMI diagnostic codes. Those codes belong to the later turbocharged 311B/311C/311D LRR siblings, which use electronically governed engines and a Cat monitoring system.	Not a fault - reflects the mechanical, pre-electronic design of this engine and machine generation.	Do not expect a code readout. Diagnose with mechanical/electrical troubleshooting per the O&M and service manual: gauge readings, pressure/temperature checks, and continuity tests rather than a digital service tool.
Red lamp - engine oil pressure	Warning lamp on the dash lights when engine oil pressure sensed by a simple pressure switch drops below the safe minimum.	Low oil level, failing oil pump, plugged oil filter, worn bearings, or a faulty pressure switch/sender.	Shut the engine down as soon as it is safe to do so. Check oil level and filter condition before restarting; do not run the engine with this lamp lit.
Red lamp - engine coolant temperature	Warning lamp lights when coolant temperature, sensed by a temperature switch, exceeds the normal operating range.	Low coolant level, debris-clogged radiator or hydraulic oil cooler fins, failed thermostat, slipping or broken fan belt.	Reduce load and let the engine idle down. Once safe, check coolant level and inspect the radiator/cooler core and belt for damage or blockage.
Amber lamp - air filter restriction	Indicator lights when the air intake filter element restriction reaches its service limit.	Dirty or clogged primary air filter element, damaged or pinched intake hose.	Inspect and service or replace the air filter element; check intake ducting for cracks or collapse.
Amber lamp - charging system	Indicator lights when the alternator is not supplying adequate charging voltage to the batteries.	Loose or worn alternator drive belt, failed alternator, corroded or loose wiring connections.	Check belt tension and battery/alternator connections; test alternator output and replace if it will not charge.

Prefix	Identifies	Notes
9LJ	Base 311, standard production PIN block (9LJ1-UP, with a documented internal break at 9LJ262-UP)	Main production prefix for the base 311 hydraulic excavator, fitted with the Cat 3064 naturally aspirated diesel (about 59 kW / 79 hp). Matches an actual 1994-built unit (9LJ00279) with the 3064 engine. Shares its electrical schematic set with the 312's 6GK block for machines built in the same era, so wiring documentation is issued jointly for 311 & 312. Treat this as the reference prefix for the base 311 - other 311 prefixes get cross-walked back to it for parts and service lookups. Base 311 production runs about 1994-1997, ahead of the 311B.
5PK	Japan-built export/parallel-import unit, otherwise identical to the 9LJ-prefix 311	Same base 311 chassis and Cat 3064 engine as the 9LJ machine, sold through non-factory-authorized export channels in some markets (sometimes called a parallel-import or grey-market unit). Cross-reference rule: 5PK serial under roughly 1000 matches a 9LJ machine of S/N 261 or below; 5PK serial at or above roughly 1000 matches a 9LJ machine of S/N 262 or above. Order parts and pull service data using the equivalent 9LJ range.
2KM	Base 311, separate production PIN block, 3064 engine	A distinct machine serial prefix documented for the base 311 alongside 9LJ, also paired with the Cat 3064 engine and starting its own 1-up numbering; seal-kit and service-manual listings cover 2KM1-UP and 9LJ1-UP as the same base-311/3064 coverage. Confirm with dealer - regional/plant assignment and exact production span were not separately documented beyond the manual coverage itself.