________________________________________________________________________________

Caterpillar 3406C Engine

The Caterpillar 3406C is a heavy-duty, inline 6-cylinder, four-stroke diesel engine renowned for its extreme durability, mechanical simplicity, and reliability across industrial, marine, and power-generation platforms. As one of the final iterations in the legendary 3406 mechanical lineage, the 3406C utilizes highly robust internal hardware and traditional hydromechanical governing, making it a preferred choice in global, non-regulated areas that require dependable performance without complex electronic controls.

The 3406C features a fully mechanical, direct-injection fuel system optimized for precision fuel metering and atomization. A low-pressure mechanical fuel transfer pump draws fuel from the supply tank, routing it through a primary fuel filter/water separator and a secondary high-efficiency fuel filter. The clean fuel enters the fuel gallery of a dedicated, engine-mounted fuel injection pump housing. Inside the housing, an internal camshaft actuates individual, high-pressure plunger pumps dedicated to each cylinder. These individual pumps compress and meter the exact amount of fuel required, pulsing it through heavy-wall steel fuel lines to mechanical fuel injection nozzles located in each cylinder head. The nozzles feature multi-hole tips that atomize the fuel into a fine mist directly within the combustion chamber. Engine speed, load response, and fueling limits are physically controlled by a hydromechanical governor paired with a mechanical fuel ratio control valve to minimize exhaust smoke during acceleration. A manual fuel priming pump is standard to purge air from the system during fuel service.

The lubrication system is a full-pressure, wet-sump configuration supplied by a high-capacity, gear-driven oil pump. The pump draws engine oil from the rear-sump oil pan through a suction screen, pushing it directly through an integrated water-cooled oil cooler and a high-efficiency spin-on lube oil filter assembly. An internal oil pressure relief valve manages system pressure spikes. Pressurized oil channels into the primary cylinder block gallery to lubricate the main bearings, connecting rod journals, camshaft bearings, and overhead valve mechanism. Piston cooling nozzles route oil directly to the undersides of the pistons to control crown temperatures. The system also supplies pressurized oil directly to the fuel injection pump housing and the hydromechanical governor center housing to continuously lubricate internal camshaft bearings and moving components.

The engine utilizes a pressurized, closed-loop jacket water cooling system managed by a heavy-duty, gear-driven centrifugal water pump. The pump forces coolant through the engine block, around the cylinder liners, and up into the cylinder head passages to absorb combustion heat. The hot coolant passes through the water-cooled exhaust manifold and turbocharger backing (on applicable configurations) before reaching the thermostat housing. Dual or single mechanical thermostats regulate fluid flow based on operational temperature. During warm-up, coolant bypasses the main heat exchanger and routes directly back to the pump inlet. Once operating temperature is achieved, the thermostats open, routing hot coolant through a heavy-duty radiator, a keel cooling system, or an external heat exchanger. An integrated jacket water aftercooler or a dedicated corrosion-resistant aftercooler core is used to reduce air inlet temperatures downstream of the turbocharger compressor.

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3406C
Engine Type ............... 4-cycle inline 6-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 5.39 (137.0)
Engine Stroke, in (mm) ............... 6.49 (165.0)
Displacement, cu.in (L) ............... 893 (14.6)
Rated Engine Power, hp (kW) ............... 370-465 (272-345)
Rated Engine Speed, rpm ............... 1800-2100
Peak Torque ............... 1820-1960 Nm (1350-1450 lb-ft) at 1200-1400 rpm
Idle Speed ............... 600-650 rpm
Aspiration Type ............... Turbocharged and Air-to-Air Aftercooled (ATAAC)
Operating Speed ............... 2000 rpm
Compression Ratio ............... 14.5:1
Firing Order ............... 1-5-3-6-2-4
Crankshaft Type ............... Forged steel
Piston Type ............... Cast-aluminum alloy
Con Rod Type ............... Forged steel
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Gear-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 105-130

Fuel System

Fuel System ............... Direct injection
Injection Pump Type ............... Rotary
Fuel System Control ............... Mechanical
Governor Type ............... Mechanical
Fuel Injector Type ............... Multi-hole
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 57.1-65.0 (1450-1650)
Overall Width, in (mm) ............... 35.4-44.3 (900-1150)
Overall Height, in (mm) ............... 43.3-51.2 (1100-1300)
Dry Weight, lbs (kg) ............... 2640-2970 (1200-1350)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 99C (210F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 345-550 kPa (50-80 psi)
Idle oil pressure ............... 140-275 kPa (15-30 psi)
Intake Valve Clearance, in (mm) ............... 0.015-0.017 (0.38-0.43)
Exhaust Valve Clearance, in (mm) ............... 0.025-0.027 (0.64-0.69)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CH-4 or CI-4
Engine Oil Capacity, qts (L) .................. 33.6-44.1 (32.0-42.0)
Coolant Capacity, qts (L) ............... 31.5-47.3 (30.0-45.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 500 hours
Inspect air filter ............... Every 100 hours
Change coolant ............... Every 2 years
Valve-lash adjustment ............... Every 1000 hours
Injector inspection ............... Every 1000-1500 hours
Compression test ............... Every 2000 hours
Drain water separator ............... As required
Belt inspection ............... As required

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ................ 5.400-5.402 (137.16-137.21)
Crankshaft Journal Outside Diameter, in (mm) ................ 4.7500-4.7512 (120.650-120.680)
Crank Pin Outside Diameter, in (mm) ................ 3.5000-3.5012 (88.900-88.930)
Crankshaft End Play, in (mm) ................ 0.005-0.021 (0.13-0.53)
Intake Valve Stem Outside Diameter, in (mm) ................ 0.3715-0.3725 (9.436-9.462)
Exhaust Valve Stem Outside Diameter, in (mm) ................ 0.3705-0.3715 (9.411-9.436)
Intake Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3735-0.3745 (9.487-9.512)
Exhaust Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3735-0.3745 (9.487-9.512)
Intake Valve Stem to Guide Clearance, in (mm) ................ 0.0010-0.0030 (0.025-0.076)
Exhaust Valve Stem to Guide Clearance, in (mm) ................ 0.0020-0.0040 (0.051-0.102)
Intake Valve Spring Free Length, in (mm) ................ 2.49 (63.2)
Exhaust Valve Spring Free Length, in (mm) ................ 2.49 (63.2)
Intake Cam Height, in (mm) ................ 2.285-2.297 (58.04-58.34)
Exhaust Cam Height, in (mm) ................ 2.245-2.257 (57.02-57.32)
Piston Pin Outside Diameter, in (mm) ................ 2.0000-2.0004 (50.800-50.810)
Piston Pin to Piston Bore Clearance, in (mm) ................ 0.0004-0.0012 (0.010-0.030)
Top Ring Side Clearance, in (mm) ................ 0.0035-0.0055 (0.089-0.140)
Second Ring Side Clearance, in (mm) ................ 0.0025-0.0045 (0.064-0.114)
Oil Ring Side Clearance, in (mm) ................ 0.0015-0.0035 (0.038-0.089)
Top Ring End Gap, in (mm) ................ 0.0200-0.0340 (0.508-0.864)
Second Ring End Gap, in (mm) ................ 0.0180-0.0300 (0.457-0.762)
Oil Ring End Gap, in (mm) ................ 0.0150-0.0270 (0.381-0.686)

Tightening Torque Specs

Cylinder head bolts ................ 270-310 Nm (199-229 lb-ft)
Main bearing caps ................ 400-450 Nm (295-332 lb-ft)
Connecting rods ................ 155-175 Nm (114-129 lb-ft)
Flywheel bolts ................ 380-420 Nm (280-310 lb-ft)
Crankshaft pulley bolt ................ 450-500 Nm (332-369 lb-ft)
Oil drain plug ................ 50-70 Nm (37-52 lb-ft)
Injector hold-downs ................ 35-45 Nm (26-33 lb-ft)

________________________________________________________________________________________

• Caterpillar Engines Specs
  
• Cat 3406E Specs
  
• Cat 3408 Specs
  
• Cat 3408C Specs
  
• Cat 3408E Specs
  

________________________________________________________________________________

________________________________________________________________________________________

_______________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________