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Caterpillar 3406E Engine

The Caterpillar 3406E represents a revolutionary milestone in heavy-duty diesel engineering, introducing full electronic control to the legendary 3406 platform in 1993. It is a highly celebrated, inline-six electronic diesel engine designed for over-the-road trucks, marine vessels, and heavy industrial machinery. By replacing the traditional mechanical injection pump and external lines with an overhead camshaft and Electronic Unit Injectors (EUI), Caterpillar dramatically improved fuel atomization, emissions compliance, and cold-start reliability. Retaining the rugged cast-iron block, robust wet-sleeve cylinder liners, and heavy-duty bottom end of its predecessors, the 3406E is widely considered one of the most reliable, high-performance, and easily programmable million-mile engines ever built.

The 3406E utilizes an advanced Electronic Unit Injection (EUI) fuel system, completely eliminating the traditional external high-pressure injection pump and steel lines. A fuel transfer pump draws fuel from the storage tank, pushing it through a primary water separator, an Electronic Control Module (ECM) cooling plate, and a high-efficiency secondary fuel filter into a low-pressure fuel gallery machined directly into the cylinder head. Injection pressure and timing are controlled by individual Electronic Unit Injectors located in each cylinder, which are mechanically actuated by an overhead camshaft via rocker arms. The engine's Electronic Control Module (ECM) monitors real-time sensor data—including boost pressure, engine speed, and throttle position—to precisely energize the internal solenoid valve on each injector. This achieves optimal injection timing, duration, and ultra-high injection pressures directly within the combustion chamber for maximum fuel efficiency and minimal smoke.

The lubrication architecture utilizes a high-capacity, pressure-regulated wet-sump system driven by a gear-type oil pump mounted inside the oil pan. The pump draws engine oil from the sump through a suction screen and forces it directly into an integrated engine oil cooler core. After temperature reduction, the fluid flows through a dual, spin-on, full-flow filter assembly equipped with internal bypass valves to maintain oil flow during cold starts or in the event of filter plugging. Filtered oil enters the main oil gallery in the cylinder block, distributing pressurized lubrication to the crankshaft main bearings, connecting rod journals, and camshaft bearings. Target-directed cooling jets spray oil at the undersides of the pistons to dissipate combustion heat. The overhead camshaft and valve train are lubricated via a dedicated oil passage rising through the block and cylinder head, while external supply and return lines provide pressurized cooling and lubrication to the turbocharger bearings.

The cooling loop is a pressurized, closed-circuit configuration circulated by a high-output, gear-driven centrifugal water pump positioned on the front timing gear housing. The pump forces coolant into the cylinder block jacket, distributing fluid evenly around the cylinder liners and upward through the cylinder head to absorb thermal energy from the combustion chambers. The circuit includes integrated flow channels for the engine oil cooler and an Air-to-Air Aftercooler (ATAAC) or Jacket Water Aftercooler (JWAC), depending on the specific application. System temperature is managed by dual mechanical thermostats housed in the upper front section of the cylinder head. During engine warm-up, the thermostats remain closed, directing coolant through a bypass pipe back to the water pump inlet. Upon reaching normal operating temperature, the thermostats open to channel hot coolant out to the radiator or marine heat exchanger.

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3406E
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) ............... 300-550 (224-410)
Rated Engine Speed, rpm ............... 1800-2100
Peak Torque ............... 1800-2480 Nm (1350-1840 lb-ft) at 1200-1500 rpm
Idle Speed ............... 550-650 rpm
Aspiration Type ............... Turbocharged and Air-to-Air Aftercooled (ATAAC)
Operating Speed ............... 2000 rpm
Compression Ratio ............... 16.0:1-17.0:1
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 ............... 60-120

Fuel System

Fuel System ............... Electronic Unit Injection (EUI)
Fuel Pump Type ............... Gear-type, transfer
Governor Type ............... Electronic
Injection Pressure, bar ............... 1200
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 57.1-62.0 (1450-1580)
Overall Width, in (mm) ............... 37.4-45.3 (950-1180)
Overall Height, in (mm) ............... 45.3-53.2 (1150-1350)
Dry Weight, lbs (kg) ............... 2640-3080 (1200-1400)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 300-450 kPa (44-65 psi)
Idle oil pressure ............... 100-150 kPa (15-22 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) ............... 40.0-57.3 (40.0-55.0)

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 ................ 340 Nm (250 lb-ft)
Connecting rods ................ 190 Nm (140 lb-ft)
Flywheel bolts ................ 380-420 Nm (280-310 lb-ft)
Crankshaft pulley bolt ................ 450-500 Nm (332-369 lb-ft)
Oil pan bolts ................ 55 Nm (41 lb-ft)
Unit injector clamp bolt ................ 35 Nm (26 lb-ft)

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

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