Caterpillar 3306C
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar 3306C is a mechanically governed, inline-six diesel built for vocational and medium-duty truck service: dump trucks, cement mixers, refuse trucks, and delivery/step-van chassis from major North American truck builders. It displaces 10.5 L (638 cu in) from a 121 mm bore and 152 mm stroke (4.75 in x 6.00 in), and Caterpillar offered it naturally aspirated, turbocharged, and turbocharged-aftercooled, with truck ratings commonly landing near 224 kW (300 hp) depending on configuration. Dry engine weight runs roughly 930-1,010 kg (2,050-2,220 lb) bare, more once dressed with truck-specific accessories. The 3306C is the late, direct-injection generation of a family that traces back to 1973, when it replaced Caterpillar's earlier 1673 and 3160 engines; the platform stayed in production for two decades before Caterpillar shifted on-highway and vocational power to the 3176 and its electronically governed C10/C12 successors.
Across the 3306 family, the defining change was the fuel system: early precombustion-chamber engines gave way to direct injection on the 3306B and 3306C, running a scroll-metering pump in place of the older sleeve-metering design, for better fuel economy and less smoke. Bore, stroke, and core block architecture carried over largely unchanged through that transition. The 3306C's fully mechanical governance - no ECM, no electronic unit injectors - is exactly why it still matters in the used and parts market today: fleets that want to avoid electronic diagnostics and emissions-system complexity keep these engines running well past their original design life, and decades of vocational-truck production left a deep, still-active supply of rebuild kits, injection components, and remanufactured long blocks.
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 3306C specifications
Engine
| Configuration | Inline 6-cylinder, 4-stroke-cycle diesel. Late-production truck-rated units use direct injection; earlier 3306 production used a precombustion-chamber design. Turbocharged, with either jacket-water aftercooling or air-to-air aftercooling depending on rating. |
| Displacement | 10.5 L (638 cu in) |
| Bore x stroke | 121 mm x 152 mm (4.75 in x 6.00 in) |
| Compression ratio | About 15.3:1 on turbocharged truck ratings |
| Gross power (on-highway/truck ratings) | 153-224 kW (205-300 hp) at 2000 rpm. Lower ratings use jacket-water aftercooling; the top 224 kW (300 hp) rating uses air-to-air aftercooling. Exact figure depends on the specific rating code ordered. |
| Emissions tier | Mechanically governed, pre-emissions-regulation diesel. Predates EPA on-highway diesel emissions standards. Cat phased this engine out of on-highway truck use through the 1990s as emissions rules tightened, replacing it with the 3406 and later C-series on-highway engines. |
Weights
| Dry weight (bare engine) | Approx. 1,100-1,400 kg (2,425-3,086 lb) depending on flywheel housing, accessory drive, and turbocharger/aftercooler configuration. A commonly cited baseline figure is about 1,120 kg (2,469 lb). |
Dimensions
| Overall length | Approx. 1,300-1,500 mm (51.2-59.1 in), varies with flywheel housing and front accessory drive |
| Overall width | Approx. 850-950 mm (33.5-37.4 in) |
| Overall height | Approx. 1,050-1,250 mm (41.3-49.2 in) |
Performance
| Peak torque | Approx. 750-1,200 N*m (553-885 lb-ft), peaking around 1,200-1,500 rpm. Exact figure tracks the power rating ordered. |
| Governed speed | 2,000-2,200 rpm full load, rating-dependent |
| Idle speed | 650-750 rpm |
| Brake specific fuel consumption | Approx. 213-249 g/kWh (0.35-0.41 lb/hp-hr), best at mid-range load; varies by rating and rpm |
Service capacities (summary)
| Engine oil (crankcase, with filter) | 27-34 L (28.5-36.0 US qt), varies by oil pan configuration |
| Cooling system (engine-side) | Roughly 18-50 L (4.8-13 US gal) depending on the installed radiator or keel-cooling setup; the engine block plus standard reservoir alone is commonly cited near 18 L (4.8 US gal). |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
3306C fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | 27.4 L (7.3 US gal) at refill per the factory engine spec sheet for this block family; total system capacity varies by configuration (naturally aspirated, turbocharged, turbocharged-aftercooled) and oil pan/cooler fitment, with field-reported totals ranging up to about 32 L (34 US qt) — verify against the sump dipstick markings for the specific chassis fitment | Cat Diesel Engine Oil (DEO), multigrade SAE 10W-30 or SAE 15W-40; single-grade SAE 30 or SAE 40 acceptable where ambient temperature stays warm and stable. Pick viscosity off Cat's ambient-temperature chart: lighter multigrades for cold-start regions, straight 40-weight for consistently hot climates. |
| Cooling system (engine only) | 15.9-18.2 L (4.2-4.8 US gal) engine-only, depending on configuration: naturally aspirated/turbocharged models run about 15.9 L (4.2 US gal), turbocharged-aftercooled models run about 18.2 L (4.8 US gal). This is the engine block/head/aftercooler circuit only — total vehicle cooling-system volume, set by the truck OEM's radiator and hose routing, is not part of this engine's own refill chart and commonly runs well above the engine-only figure; check the chassis manufacturer's data for the installed total. | Cat DEAC (Diesel Engine Antifreeze/Coolant), a conventional low-silicate heavy-duty coolant maintained with a Supplemental Coolant Additive (SCA) at scheduled intervals; Cat ELC (Extended Life Coolant) is the low-maintenance alternative when used from first fill, eliminating SCA additions and stretching the change interval. Mix with clean, distilled or deionized water per the label ratio; do not mix DEAC and ELC chemistries. |
| Fuel tank | Not applicable — this is a bare truck engine; the fuel tank is supplied and sized by the truck chassis manufacturer, not covered by this engine's own refill chart. | Standard No. 2-D diesel fuel meeting Cat's fuel specification; use winterized/No. 1-D blends in cold climates to control cold-flow properties. |
| Grease (spec only) | Spec only — applied at fan hub and idler pulley grease fittings where equipped; no refill volume published for this engine. | Cat Multipurpose Grease (MPGM), NLGI No. 2 for general service; NLGI No. 1 in sustained sub-freezing climates for easier pumpability through the fittings. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar 3306C maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 7,500 h |
|
| Every 15,000 h |
|
Servicing the 3306C beyond the schedule
Predictive Maintenance & Fluid Analysis
With no ECM to flag faults, oil sampling is the 3306C's main early-warning system - track wear metals for liner and ring wear, and watch for coolant intrusion signaling a head gasket or wet-liner seal starting to fail. Sample fuel periodically; the mechanical injection pump and scroll-metering system are sensitive to sludge and water contamination that clog injectors. Log turbocharger boost pressure and exhaust temperature trends at each service interval to catch bearing wear or a cracked charge-air hose before it costs power or fuel economy.
Corrective & Common Repairs
Expect injection pump fuel seepage near the exhaust manifold - treat it as a fire risk, not a nuisance leak. Governor shaft corrosion causes hard starting or a no-start; free and lubricate it before condemning the pump. Diesel sludge and water in the tank clog filters and injectors, showing up as power loss or stalling under load. After any overheating event, check for a blown head gasket or warped head before returning the truck to service, and replace worn charge-air boots that let unfiltered air past the turbo.
Overhaul & Rebuild Points
Cylinder liner and ring wear are the usual overhaul trigger on a 3306C running high hours; oil consumption and blow-by are the tell. Cracked heads around valve seats and injector bores show up on engines that saw repeated overheating cycles typical of stop-and-go vocational routes. An in-frame overhaul - pistons, rings, liners, rod and main bearings - buys a comparable second service life, and the injection pump/governor is usually rebuilt at the same time. Decades of production left a deep parts and remanufactured long-block supply that keeps overhaul costs reasonable.
Seasonal & Environment Servicing
Cold starts are the mechanical governor's weak point - verify the ether or glow-plug starting aid before winter and drain the water separator more often as condensation increases. Fuel gelling in cold climates demands a winter-blend or additive plan given the era-correct fuel system's tolerance for wax. In hot, dusty vocational duty (mixers, refuse routes), clean the charge-air cooler and radiator fins more often and shorten the air filter service interval to protect the direct-injection system from abrasive dust ingestion.
3306C common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 1D-4540 | Bolt,Machine Fuel Filter Mounting | Fuel system service | Check fitment → |
| 1R-0750 | Filter As-Fuel | Fuel system service | Check fitment → |
| 4W-9057 | Tube As | Fuel system service | Check fitment → |
| 1W-6629 | Tube As-Fuel Filter | Fuel system service | Check fitment → |
| 134-3589 | Film-Information | Fuel system service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
3306C fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Low Oil Pressure Warning (dash lamp / buzzer) | Oil pressure contactor switch signals that engine oil pressure has dropped below its set threshold. | Low oil level, worn or failing oil pump, plugged oil filter, worn bearings, or a faulty pressure switch. | Stop the engine, verify oil level, and confirm actual pressure with a mechanical gauge before restarting. Do not continue running on the lamp alone. |
| High Coolant Temperature Warning (dash lamp / buzzer) | Water temperature sending unit trips a contact switch once coolant temperature exceeds its set point. | Low coolant level, stuck thermostat, blocked radiator or oil cooler, failed water pump, or slipping fan drive. | Idle down and check coolant level and radiator/oil cooler flow once safe. Verify actual temperature with a shop gauge and inspect the thermostat and water pump if the lamp recurs. |
| Overspeed Shutdown | Overspeed contactor switch trips when engine rpm exceeds the governor's safe limit, energizing the fuel rack shutoff solenoid to stop the engine. | Sudden loss of load (driveline disconnect), governor linkage failure, or a runaway condition from turbocharger oil ingestion. | Do not restart until the cause is found and cleared. Inspect governor linkage, driveline, and turbocharger seals before returning to service. |
| Automatic Engine Shutdown (fuel rack shutoff solenoid trip) | Shutoff solenoid energizes and moves the injection pump fuel rack to the off position, stopping the engine. Can be triggered by the oil pressure, coolant temperature, or overspeed switches, or by a remote shutdown switch. | Any upstream alarm condition reaching its shutdown threshold, or a wiring/solenoid fault causing a false trip. | Trace which upstream switch energized the solenoid before assuming a solenoid fault. Check switch continuity and the shutdown wiring harness. |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
3306C attachments & work tools
Air compressor / air-brake system
A gear-driven air compressor feeds the truck air-brake circuit on 3306C truck arrangements; output is matched to the chassis air-tank sizing rather than one fixed spec. Standard equipment on vocational and on-highway builds of this engine.
Alternator / charging system
Factory charging options for truck arrangements run roughly 24V in the 35-100A range, with some lighter-duty chassis using 12V units; rating is picked to suit the vocational body load (mixer, dump, refuse). Exact output varies by arrangement number.
Engine (compression-release) brake
A Jacobs-type engine brake is offered as a factory or dealer-fit option on many 3306C truck arrangements, mounted at the front or rear of the cylinder head depending on chassis packaging. Fitment is tied to specific serial/arrangement ranges, so confirm compatibility before ordering.
Flywheel and flywheel housing (clutch/transmission mount)
An SAE No. 1 flywheel housing is the standard mount for the 3306C truck engine, mating it to manual clutch or heavy-duty automatic (Allison/Fuller-class) transmissions common in this size class. Flywheel face and ring-gear pattern follow the same SAE No. 1 bolt circle used across comparable truck diesels.
Aspiration / power-rating configuration
Truck-rated 3306C engines were built naturally aspirated, turbocharged, and turbocharged-aftercooled, spanning roughly 170-300+ kW (230-400+ hp) depending on rating and duty cycle. Aftercooled ratings require the matching aftercooler and radiator cooling package; do not mix aftercooled fueling with a non-aftercooled cooling set.
Cooling system / fan drive
Water pump drive is belt- or gear-driven depending on arrangement, and the fan is carried on a clutch-type drive (viscous or on/off) sized to the vocational cooling package rather than a fixed direct drive. Cooling package must be matched to the chassis radiator and duty cycle, especially on aftercooled ratings.
Cold-start aid
An ether-injection starting aid is available for cold-climate operation on truck arrangements of the 3306C. Base mechanical arrangements use a manually actuated system; treat any automated/ECM-cycled ether control as belonging to later electronically governed Cat truck engines, not the core 3306C.
Governor and fuel system
Truck 3306C engines use a mechanically governed injection pump with adjustable timing rather than full electronic (ECM) control. Injection timing and fuel setting are arrangement-specific and must match the intended horsepower rating; period literature also references the same core engine under related truck designations such as direct-injection (DI) and PC variants.
Accessory drive train
Air compressor, power-steering pump, and water pump commonly run off gear drives rather than belts on the 3306C, cutting belt-slip maintenance versus belt-driven competitors of the era. This gear-train layout is a characteristic feature of the 3300-series truck engine package.
Power take-off (PTO) provisions
PTO capability on 3306C-powered trucks is normally provided through the transmission (Allison/Fuller-class units) rather than an engine-integrated front pad. A dedicated engine-mounted front PTO is not well documented for this truck arrangement, so confirm availability with the chassis or transmission builder rather than assuming a standard fitment.
All 3306C assemblies by section
Every catalogued assembly group for the Caterpillar 3306C. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Air Inlet And Exhaust System
7c-1653 Lines Gp-Air
| 4L***37 | Seal To Aftercooler Elbow | 2 |
| 7C***53 | Lines Group-Air | 1 |
| 7W***97 | Elbow--90 Degree | 1 |
9l-5805 Manifold Gp-Exhaust
| 0S***14 | Bolt (.25" Diameter-.50" Long) | 1 |
| 1W***48 | Support Assem. | 1 |
| 1W***49 | Shield As-Manifold | 1 |
155-5463 Turbocharger Gp
| 10***08 | Hose | 1 |
| 15***63 | Turbocharger Group | 1 |
| 4P***66 | Clamp; (Compressor) | 2 |
155-7899 Turbocharger Gp
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 2 |
| 15***63 | Turbocharger Group | 1 |
| 15***99 | Turbocharger Group | 1 |
Basic Engine
1w-0592 Pan Gp-Oil
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 12 |
| 16***00 | Gasket; (Oil Pan) | 1 |
| 1A***29 | Bolt (1-1/8") Tube Assembly To Transfer Drive Case | 26 |
3n-2886 Adapter Gp-Seal
| 0L***29 | Bolt- 7.63 cm(3 In.) Long - Location "H" | 2 |
| 1W***06 | Adapter-Seal | 1 |
| 2P***92 | Seal (Id=133.02mm) | 1 |
110-5765 Air Compressor Gp
| 0S***89 | Bolt, Hex. Hd., 5/8"-11 N.C. X 1 3/4" | 2 |
| 10***17 | Air Compressor Group | 1 |
| 11***65 | Air Compressor Group | 1 |
109-1317 Air Compressor Gp
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 5 |
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 14 |
| 0T***65 | Bolt--3/8" X 3 1/2"--Use As Required; Bolt 5t***56 Plate To Cover Gp 4n***72 | 1 |
110-5764 Air Compressor Gp
| 11***64 | Air Compressor Group | 1 |
| 15***46 | Kit-Unloader; (Air Compressor) | 1 |
7e-9777 Camshaft Gp
| 0S***09 | Bolt (3/4") Filler Tube Assembly To Transfer Drive Case | 2 |
| 7E***61 | Camshaft | 1 |
| 7E***77 | Camshaft Group | 1 |
7n-1342 Cover Gp-Cylinder Block
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
| 2A***98 | Pin,Straight,Headle Flywheel Housing | 2 |
| 4B***38 | Plug 28.95 mm(1.14 In.) Hole Dia. | 1 |
7c-0272 Cover Gp-Cylinder Head
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 4 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 1 |
| 11***03 | Tube As | 1 |
3n-4923 Cover Gp-Front Housing
| 0S***66 | Bolt-Pulley To Crankshaft Adapter | 4 |
| 2P***20 | Gasket-- Front Cover | 1 |
| 2S***41 | Plug 2.14 In. (5.43 cm) Diameter | 1 |
8n-4745 Cover Gp-Valve Mechanism
| 13***47 | Seal-Integral; (Valve Cover) | 1 |
| 2B***95 | Cap Screw--Tube Assembly To Air Inlet Pipe | 15 |
| 2W***86 | Cover As-Cylinder Head | 1 |
4p-9856 Crankshaft Gp
| 10***52 | Plate-Thrust | 2 |
| 19***34 | Kit-Basic Engine Repair; (Main Bearing)(Crankshaft) | 0 |
| 23***33 | Bearing-Main; (Standard)(Standard) | 7 |
7n-6550 Cylinder Block Gp
| 10***12 | Insert; (Liner Seat) (.822-mm Thk) | 6 |
| 10***18 | Insert; (Liner Seat) (1.605-mm Thk) | 6 |
| 10***27 | Insert-Liner Seat (2.710mm Thk) | 6 |
1n-3576 Cylinder Block Gp
| 1N***76 | Cylinder Block Group | 1 |
| 1S***40 | Dowel; (30.23 mm X 9.37 mm) | 1 |
| 2S***58 | Washer-Hard; (17x29x3-mm Thk)(Engine Brake) | 14 |
8n-5286 Cylinder Block Gp
| 11***50 | Gasket-Plate | 1 |
| 1S***40 | Dowel; (30.23 mm X 9.37 mm) | 1 |
| 3S***96 | Seal-O-Ring; (9.53mm Id) | 1 |
4p-9669 Cylinder Head As
| 10***65 | Insert-Valve Seat; (Exhaust)(Standard) | 6 |
| 10***68 | Insert-Valve Seat; (Inlet)(Standard) | 6 |
| 13***96 | Cylinder Head As | 1 |
4p-9670 Cylinder Head Gp
| 10***60 | Valve (Intake) | 6 |
| 11***15 | Gasket As-Cylinder Head | 1 |
| 14***55 | Valve-Exhaust | 6 |
9n-2345 Damper Gp
| 0S***87 | Bolt-Bracket Assembly To Timing Gear | 6 |
| 16***23 | Damper Assem. | 1 |
| 5P***45 | Washer-Hard; (13.5x25.5x3-mm Thk)(Turbocharger Blanking Plate) | 6 |
7n-9536 Fastener Gp-Cylinder Head
| 1B***09 | Bolt-- Head To Cylinder Block | 5 |
| 1D***95 | Bolt (5/8-11x6in); (5/8-11x6-In) | 20 |
| 2S***36 | Washer,Flat Cover Assembly Mounting And Flywheel Housing Cover | 25 |
1w-3802 Fastener Gp-Front Housing
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 17 |
| 1C***51 | Bolt--Installation Of 2v***26 Retainer | 2 |
| 1W***02 | Fastener Group-Front Housing | 1 |
154-7388 Fastener Gp-Front Housing
| 0L***29 | Bolt- 7.63 cm(3 In.) Long - Location "H" | 2 |
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 16 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 2 |
150-4983 Flywheel Gp
| 0S***01 | Bolt 2.75 In. (69.85 mm) Long | 9 |
| 15***88 | Flywheel As | 1 |
| 15***83 | Flywheel Group | 1 |
4p-9858 Gear Gp-Front
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 2 |
| 0S***18 | Bolt; (5/16-18x1-In)(Hydraulic Pump) | 2 |
| 0S***48 | Bolt,Machine Camshaft Gear Mounting | 4 |
9n-3128 Housing Gp-Flywheel
| 0S***87 | Bolt-Bracket Assembly To Timing Gear | 13 |
| 10***22 | Housing-Flywheel | 1 |
| 1B***74 | Plug,Pipe Base Assembly,Engine Oil Filter Assembly | 1 |
8n-0303 Housing Gp-Front
| 1W***00 | Gasket Timing Gear Cover | 1 |
| 1W***16 | Plate As-Front | 1 |
| 5M***14 | Pipe Plug Cylinder Block Oil Pressure | 1 |
6n-8326 Lifting Gp-Engine
| 6N***26 | Lifting Group; Lifting Eye Gp-Engine | 1 |
| 6V***99 | Bolt; (5/8-11x38.1mm) | 4 |
| 8D***54 | Washer,Flat Electric Starting Motor Group | 4 |
110-5763 Lines Gp-Air Compressor
| 11***63 | Lines Group-Air Compressor | 1 |
| 2M***80 | Seal--To Connector Pump Outlet | 1 |
| 2N***87 | Elbow-Flared Needed For Customer; (Used Without Brakesaver) | 1 |
9y-4724 Panel Gp-Sound Suppression
| 00***26 | Bolt | 1 |
| 1W***71 | Panel Assem. | 1 |
| 4B***88 | Bolt (5/16 X 28.58 mm); (5/16-18x1.125-In) | 19 |
4p-9870 Piston & Rod Gp
| 15***87 | Body As-Piston | 1 |
| 1P***56 | Bolt,Shoulder Connecting Rod | 2 |
| 1S***43 | Ring,Retaining Piston Pin | 2 |
9n-2346 Pulley Gp-Crankshaft
| 5S***48 | Washer-Special | 1 |
| 7W***94 | Pulley-Crankshaft; (2 Groove) | 1 |
| 9N***46 | Pulley Group-Crankshaft; Crankshaft Pulley Group | 1 |
2p-6224 Seal Gp-Crankshaft
| 2P***24 | Seal Group-Crankshaft; Crankshaft Seal Group | 1 |
| 4W***52 | Seal Group-Crankshaft; (Counter Clockwise Rotation) | 1 |
| 9Y***95 | Seal Group-Crankshaft; (Clockwise Rotation) | 1 |
7c-7013 Valve Mechanism Gp
| 1B***09 | Bolt-- Head To Cylinder Block | 1 |
| 1L***72 | Dowel (Part Of 8s***99 Assem.) | 1 |
| 2S***36 | Washer,Flat Cover Assembly Mounting And Flywheel Housing Cover | 1 |
7e-9778 Valve Mechanism Gp
| 2W***43 | Lifter As-Valve | 12 |
| 5S***18 | Push Rod,Engine Pop Valve Lifter | 12 |
| 7C***13 | Valve Mechanism Group | 1 |
Cooling System
172-7760 Pump Gp-Water
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
| 15***82 | Seal-Lip Type | 1 |
| 16***50 | Seal Group; (Water Pump) | 1 |
4p-9861 Pump Gp-Water
| 0T***55 | Bolt; (3/8-16x4.25-In)(Location S) | 2 |
| 17***60 | Pump Group-Water | 1 |
| 4P***61 | Pump Group-Water | 1 |
172-7768 Pump Gp-Water
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
| 15***46 | Housing-Water Pump | 1 |
| 15***82 | Seal-Lip Type | 1 |
138-2899 Pump Gp-Water
| 0T***55 | Bolt; (3/8-16x4.25-In)(Location S) | 2 |
| 13***99 | Pump Group-Water | 1 |
| 17***68 | Pump Group-Water | 1 |
4p-9862 Pump Gp-Water
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 1 |
| 13***22 | Impeller-Pump | 1 |
6i-0903 Cooler Gp-Fltr Base & Eng Oil
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 2 |
| 1R***39 | Filter As-Engine Oil; (Standard Efficiency) | 1 |
| 2W***61 | Gasket | 1 |
6i-0902 Cooler Gp-Fltr Base & Eng Oil
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 2 |
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 2 |
| 1A***29 | Bolt (1-1/8") Tube Assembly To Transfer Drive Case | 8 |
8n-0888 Regulator Gp-Temperature
| 11***10 | Regulator-Water Temperature; (91 Deg Celsius) | 1 |
| 1W***10 | Pipe-Outlet | 1 |
| 5S***82 | Capscrew; (Hex Hd) (1/2-13x1 3/8, Gd8, Z) | 4 |
119-0099 Housing & Regulator Gp
| 11***10 | Regulator-Water Temperature; (91 Deg Celsius) | 1 |
| 11***99 | Housing & Regulator Group | 1 |
| 1P***89 | Pipe-Head Outlet | 1 |
8n-4112 Lines Gp-Water
| 1B***74 | Plug,Pipe Base Assembly,Engine Oil Filter Assembly | 3 |
| 3J***90 | Plug Adapter Turbo Oil Supply; Plug-Adapter Turbo Oil Supply | 1 |
| 5M***13 | Plug To Turbocharger Lubrication Valve Body Assembly | 2 |
2w-6779 Lines Gp-Water
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 1 |
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 2 |
| 0T***65 | Bolt--3/8" X 3 1/2"--Use As Required; Bolt 5t***56 Plate To Cover Gp 4n***72 | 1 |
Electrical And Starting System
2w-8198 Shutoff Gp-Electrical
| 12***74 | Solenoid Group-Shutoff; -Governor | 1 |
| 1W***70 | Switch As-Start | 1 |
| 2A***46 | Bolt,Machine Governor Linkage Bracket | 2 |
125-5774 Solenoid Gp-Shutoff
| 12***74 | Solenoid Group-Shutoff; -Governor | 1 |
| 6V***77 | Nut (8-32 Thd) | 2 |
| 9B***33 | Lockwasher; (Int'L Tooth) | 2 |
107-5813 Starting Aid Gp
| 10***44 | Hose As-Fuel | 1 |
| 10***67 | Film-Warning; (Flamm Starting Aid) | 1 |
| 10***82 | Boss | 1 |
109-3447 Starting Aid Gp
| 03***46 | Elbow, 90 Deg Adj., 1/4in. J.I.C. X 7/16in.-14 Str. Thd. | 2 |
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 1 |
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 1 |
6v-4641 Starting Motor Gp-Electric
| 6V***41 | Starting Motor Group-Electric | 1 |
| 6V***45 | Starting Motor Group-Electric | 1 |
| 6V***46 | Starting Motor Group-Electric | 1 |
207-1546 Starting Motor Gp-Electric
| 03***23 | Bolt; (1/4-28x1-In) | 5 |
| 19***70 | Solenoid As-Starting Motor; (24-Volt)(Starting Motor) | 1 |
| 20***46 | Starting Motor Group-Electric | 1 |
6n-1678 Starting Motor Gp-Electric
| 2L***54 | Terminal-Ring; (6-Ga, 1/2-In Screw) | 2 |
| 3T***64 | Starting Motor Group-Electric | 1 |
| 4H***69 | Gasket Starter Mtg Part Of Kit P/N 5r***25 | 1 |
8c-3594 Starting Motor Gp-Electric
| 03***21 | Shim Lever Housing | 1 |
| 03***23 | Bolt; (1/4-28x1-In) | 5 |
| 2H***29 | Ring - Retaining External | 1 |
9x-4454 Starting Motor Gp-Electric
| 3E***27 | Kit-Bearing; (Starting Motor)(Incl Bearing Seals & Spacers) | 1 |
| 3E***28 | Kit; (Brush) (Includes O-Rings, Screw, Spring, & Brush) | 1 |
| 3E***29 | Kit; (Hardware) Includes Washers, Bolts, Lockwashers, Nuts, Bushings, & Plate) | 1 |
3t-2371 Starting Motor Gp-Electric
| 3T***42 | Bearing Assem. | 1 |
| 3T***44 | Kit-Brush; (Includes 4 Brushes) | 1 |
| 3T***47 | Screw-Special; (M5x10-Thd, M5x13-Thd) | 4 |
3t-2764 Starting Motor Gp-Electric
| 3T***71 | Starting Motor Group-Electric; Electric Starting Motor Group | 1 |
| 3T***64 | Starting Motor Group-Electric | 1 |
| 8C***94 | Starting Motor Group-Electric; Starting Motor Gp-Electric-Delco-Remy | 1 |
6v-4940 Starting Motor Gp-Electric
| 3E***25 | Cover As; (Starting Motor) | 1 |
| 3E***27 | Kit-Bearing; (Starting Motor)(Incl Bearing Seals & Spacers) | 1 |
| 3E***28 | Kit; (Brush) (Includes O-Rings, Screw, Spring, & Brush) | 1 |
6v-4646 Starting Motor Gp-Electric
| 03***21 | Shim Lever Housing | 1 |
| 03***23 | Bolt; (1/4-28x1-In) | 5 |
| 2H***29 | Ring - Retaining External | 1 |
6v-4645 Starting Motor Gp-Electric
| 5C***74 | Nut (M5x.8 Thd); (M5x0.8-Thd) | 2 |
| 6V***45 | Starting Motor Group-Electric | 1 |
| 7X***62 | Washer-Hard; (13.5x19x0.8-mm Thk) | 5 |
207-1545 Starting Motor Gp-Electric
| 20***45 | Starting Motor Group-Electric | 1 |
| 20***46 | Starting Motor Group-Electric | 1 |
| 6V***40 | Starting Motor Group-Electric | 1 |
Engine Arrangement
150-4982 Engine Ar
| 14***48 | Kit-Gasket; (Fuel System)(Fuel System) | 0 |
| 14***28 | Kit-Gasket; (Single Cylinder Head) | 0 |
| 14***62 | Kit-Gasket; (Rear Structure)(Rear Structure) | 0 |
Fuel System
7c-8993 Fastener Gp-Fuel Inj Pump
| 0S***14 | Bolt (.25" Diameter-.50" Long) | 3 |
| 2S***83 | Bolt (3.25" Long-Drilled Head) | 1 |
| 4F***57 | Screw,Cap,Hexagon H Shock Mount To Bracket | 8 |
1w-8668 Torque Control Gp
| 1P***52 | Insulator,Bushing Governor | 1 |
| 1W***68 | Torque Control Group | 1 |
| 2P***85 | Spacer (.635 mm Thk); (0.635-mm Thk) | 1 |
4p-2507 Control Gp-Fuel Ratio
| 10***93 | Washer | 1 |
| 11***58 | Washer; (12.7x6.65x0.79-mm Thk) | 1 |
| 1B***01 | Nut Generator Line Leads; Nut-Generator Line Leads | 1 |
8n-2177 Control Gp-Governor
| 1M***54 | Screw | 1 |
| 3N***92 | Lever-Governor Control | 1 |
| 8N***77 | Control Group-Governor; Governor Control Group | 1 |
2w-1011 Filter Gp-Fuel
| 03***47 | Elbow-Filtered Fuel From Based Assembly | 2 |
| 1R***50 | Filter As-Fuel; (Advanced Efficiency)(Secondary) | 1 |
| 2W***11 | Filter Group-Secondary; (Secondary) | 1 |
2w-2410 Governor Gp
| 03***16 | Bolt-Self Locking; (1/4unc X 3/4) | 3 |
| 0S***16 | Screw,Cap,Hexagon H Receptacle Mtg; Bolt Brackets To Firewall Assembly | 6 |
| 13***07 | Seal-Lip Type; (6.39mm) | 1 |
4w-3834 Lines Gp-Fuel Drain
| 03***47 | Elbow-Filtered Fuel From Based Assembly | 1 |
| 1W***29 | Tube As-Fuel Filter | 1 |
| 3J***07 | Seal Valve Assembly To; Seal- Tube Assembly To Logic Valve | 1 |
100-4634 Lines Gp-Fuel Injection
| 10***35 | Line As-Fuel Injection | 1 |
| 10***36 | Line As-Fuel Injection | 1 |
| 10***34 | Lines Group-Fuel Injection | 1 |
100-4635 Lines Gp-Fuel Injection
| 10***31 | Line As-Fuel Injection | 1 |
| 10***32 | Line As-Fuel Injection | 1 |
| 10***33 | Line As-Fuel Injection, .. Idler, . Idler | 1 |
4p-9889 Lines Gp-Fuel Injection
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 1 |
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 1 |
| 10***34 | Lines Group-Fuel Injection | 1 |
4p-9827 Pump Gp-Fuel Injection
| 1W***87 | Valve As-Check; (Fuel Injection Pump) | 1 |
| 4P***27 | Pump Group-Fuel Injection | 1 |
| 4P***30 | Plunger & Barrel Assem. | 1 |
4p-9841 Pump Gp-Fuel Injection
| 0S***15 | Bolt 19 mm (.75 In.) Long Return Air Console To Enclosed Rops | 4 |
| 11***18 | Seal-O-Ring; (26.64mm Id) | 6 |
| 15***24 | Gasket-Timing | 1 |
4w-1876 Pump Gp-Fuel Priming
| 03***94 | Connector-Flared | 1 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 1 |
| 0S***18 | Bolt; (5/16-18x1-In)(Hydraulic Pump) | 1 |
1w-1695 Pump Gp-Fuel Transfer
| 0S***15 | Bolt 19 mm (.75 In.) Long Return Air Console To Enclosed Rops | 2 |
| 1W***69 | Piston | 1 |
| 1W***95 | Pump Group-Fuel Transfer | 1 |
2w-4160 Pump & Mtg Gp-Fuel Transfer
| 1W***95 | Pump Group-Fuel Transfer | 1 |
| 2W***60 | Pump Group-Fuel Transfer & Mtg; Fuel Transfer Pump And Mounting Group | 1 |
| 4B***65 | Screw,Cap,Hexagon Fuel Injection Pump | 1 |
4p-9839 Pump Gp-Gov & Fuel Inj
| 03***79 | Seal-O-Ring (Id=10.82mm) | 1 |
| 14***77 | Gasket | 1 |
| 15***26 | Gasket | 1 |
2w-9161 Shutoff Gp-Manual
| 1N***54 | Lever | 1 |
| 2W***61 | Shutoff Group-Manual; -Fuel | 1 |
| 9F***80 | Bolt 28.58 mm(1.125 In.) Long | 1 |
2w-7699 Shutoff Gp-Manual
| 15***28 | Gasket-Governor | 1 |
| 15***30 | Gasket-Governor | 1 |
| 1W***20 | Spring | 1 |
Lubrication System
7e-0571 Lines Gp-Engine Oil
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 3 |
| 11***87 | Seal-O-Ring (23.16 mm Id) | 2 |
6i-2354 Base Gp-Oil Filter
| 1B***90 | Bolt; (5/16-18x1.375-In)(Rh Front Cover) | 2 |
| 1B***75 | Bolt (" " " ); Bolt ( " " " ) | 1 |
| 1P***67 | Plunger; (Engine Oil Cooler Relief Valve) | 2 |
1p-4244 Breather Gp
| 1P***44 | Breather Group | 1 |
| 2W***62 | Breather As-Crankcase; (Engine) | 1 |
| 3H***43 | Bolt,Machine Breather Assembly To Cover | 1 |
9n-1869 Filler Gp-Engine Oil
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 3 |
| 1P***98 | Pipe-Oil Filler | 1 |
| 2P***20 | Gasket Cover,Timing Cover | 1 |
7w-1828 Fumes Disposal Gp
| 1A***79 | Capscrew (5/16 - 18 Nc X 1 1/2 Gd5, Hex) | 1 |
| 4D***88 | Clip-(Slot To Fit Fastener M10 Or 3/8) | 1 |
| 4W***81 | Hose-Disposal; (Fumes) | 1 |
155-4048 Gauge Gp-Oil Level (Dipstick)
| 15***52 | Gauge As-Oil Level | 1 |
| 15***48 | Gauge Group-Oil Level (Dipstick) | 1 |
| 2B***95 | Cap Screw--Tube Assembly To Air Inlet Pipe | 2 |
4p-9506 Lines Gp-Turbocharger Oil
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 2 |
| 10***68 | Hose As | 1 |
4p-9859 Pump Gp-Engine Oil
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 2 |
| 3B***15 | Bolt Guard Assembly To Accessory Drive Housing | 2 |
| 4P***59 | Pump Group-Engine Oil | 1 |
6i-1343 Pump Gp-Engine Oil
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 1 |
| 0T***73 | Bolt (3/8) (63.5mm Long) (On Cab Of Cover Assem.) | 2 |
| 1B***75 | Bolt (" " " ); Bolt ( " " " ) | 1 |
4p-9860 Pump Gp-Engine Oil
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 1 |
| 1P***46 | Washer-Hard; (10.2x35x6-mm Thk) | 1 |
| 4P***30 | Gear-Oil Drive; (33-Teeth) | 1 |
Service Equipment And Supplies
6l-4502 Chart-Plate & Film
| 10***64 | Film; (Identification) (Engine Oil Filter) | 1 |
| 11***52 | Plate & Film Group; -Engine Information | 1 |
| 13***89 | Film-Information; (Fuel Filter) | 1 |
3306C serial number reference
The engine serial/ID plate sits on the engine block, most commonly on the left side near the front, though some installations carry it on the valve cover or flywheel housing instead. The plate reads as a three-character prefix followed by a sequence number (for example 9TL01234); the prefix ties to the specific model and build configuration, and the digits track production sequence within that prefix. Always match the full plate serial, not just a casting or part number, when identifying the engine.
| Prefix | Identifies | Notes |
|---|---|---|
| 2AZ | 3306C Truck Engine | Mechanical inline-six diesel truck engine, turbocharged and air-to-air aftercooled (ATAAC). One of the core on-highway serial ranges for this model. |
| 7RJ | 3306C Truck Engine | Turbocharged, air-to-air aftercooled truck engine build. Covered by dedicated system operation, testing-and-adjusting, and fault-code service literature for this range alongside 9TL and 2AZ. |
| 9TL | 3306C Truck Engine | Turbocharged, air-to-air aftercooled truck engine build, commonly cited as a later-production on-highway range for this model. |
| 3KS | 3306C Truck Engine | Listed alongside 2AZ, 7RJ, and 9TL as a 3306C truck-engine serial range in dealer parts-prefix references. Cited less often elsewhere - confirm with dealer before ordering parts against this range. |
Frequently asked questions
What engine does the Caterpillar 3306C use?
The 3306C is itself Caterpillar's engine, not a machine that takes a separate power plant. It's an inline-six, 10.5 L (638 cu in) mechanical diesel - the late, direct-injection generation of the 3306 family, built naturally aspirated, turbocharged, or turbocharged-aftercooled depending on the rating ordered.
What is the operating weight of the Caterpillar 3306C?
Bare dry weight runs about 930 kg (2,050 lb) naturally aspirated up to roughly 1,010 kg (2,220 lb) turbocharged-aftercooled; fully dressed with truck-specific accessories it can reach 1,100-1,400 kg (2,425-3,086 lb). Exact figure varies by configuration and chassis installation.
What replaced the Caterpillar 3306C?
Caterpillar moved on-highway and vocational truck power to the 3176 through the 1990s, which evolved into the electronically governed C10 and C12. Those platforms were succeeded by the ACERT-equipped C9 in 2004 as emissions rules tightened further.
What 3306C owners discuss
What's the shop-floor reputation of the 3306C, and how is it different from the earlier 3306/3306B?
Does the 3306C have a jake brake / engine brake, and how well does it work?
Why is the truck hard to start or rough-running after sitting for a few days?
What injection pump and governor quirks come up specifically on the 3306C?
What cooling-system and cylinder-liner wear patterns show up as these engines rack up hours?
Are there electrical or sensor issues to worry about on the 3306C?
What should I check before buying a used 3306C truck?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific 3306C part?
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