Komatsuengine(no series)
Komatsu NT-855-1A(S/N 139838-UP)
Maintenance schedule, common problems & OEM parts breakdown
The NT-855-1A(S/N 139838-UP) is a Cummins-built, factory-fitted turbocharged diesel engine — 14.0 L (855 cu in), inline six-cylinder, mechanical PT fuel injection with no aftercooling and no electronic engine control. It is rated around 164 kW (220 hp) at 1800 rpm with roughly 1,029 Nm (759 lb-ft) of max torque. Komatsu cataloged this engine into its D80/D85-18 series crawler dozer line, offered in three drivetrain configurations built on the same core engine: a power-shift A-series host running roughly 23,310-23,610 kg (51,390-52,051 lb), a lighter direct-drive E-series host running roughly 19,000-19,300 kg (41,900-42,560 lb), and a P-series designation. The NT-855-1A succeeded the naturally aspirated NH-220-CI engine used on the earlier D80A-12/D85A-12 generation, adding a turbocharger to raise output from that smaller-displacement predecessor.
Moving from the naturally aspirated NH-220-CI to the turbocharged NT-855-1A gave the D80/D85-18 series a meaningful jump in power and pulling torque without changing the mechanical, ECM-free character of the engine — service still runs on gauges, caution lamps, and PT injection adjustment rather than fault codes. Komatsu offered that same engine across power-shift and direct-drive transmission variants, letting buyers match drivetrain complexity and weight class to the job rather than the engine choice. In the used and parts market today, this engine and its D80/D85-18 hosts remain relevant because the mechanical PT fuel system and simple electrical layout are field-serviceable without diagnostic tooling, rebuildable top ends and injector sets keep older dozers working, and demand holds for a class of heavy-push mechanical dozer that predates emissions-tier electronics.
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.
Komatsu NT-855-1A(S/N 139838-UP) specifications
Engine
| Model | NT-855, 6-cylinder turbocharged diesel (Cummins-based big-cam design); this serial range is factory-coded NT-855-1A |
| Gross power | 164 kW (220 hp) at 1800 rpm |
| Displacement | 14.0 L (855 cu in) |
| Cylinders | 6, inline, turbocharged, no aftercooling |
| Max torque | 1,029 Nm (759 lb-ft) |
| Emissions tier | Not applicable — mechanical pre-emissions-regulation industrial diesel; no tier rating published |
Weights
| Operating weight, power-shift dozer (A-series host) | 23,310-23,610 kg (51,390-52,051 lb) |
| Operating weight, direct-drive dozer (E-series host) | 19,000-19,300 kg (41,900-42,560 lb) |
| Ground pressure | 0.055-0.061 MPa (7.9-8.82 psi), varies by host configuration and shoe width |
Dimensions
| Overall length with blade (A-series host) | 6.80 m (22.3 ft) |
| Overall length without blade | 4.39-4.69 m (14.39-15.4 ft), varies by host series |
| Width over tracks | 2.62 m (8.6 ft) |
| Height to top of cab | 3.41 m (11.14-11.2 ft) |
| Ground clearance | 0.40-0.43 m (1.33-1.4 ft) |
| Track gauge | 2.00 m (6.57 ft) |
| Length of track on ground | 2.73 m (8.96 ft) |
Performance
| Max forward speed, power-shift host (5-speed) | 8.05 km/h (5 mph) |
| Max reverse speed, power-shift host | 9.5 km/h (5.9 mph) |
| Max forward speed, direct-drive host (3-speed) | 11.3 km/h (7 mph) |
| Max reverse speed, direct-drive host | 13.4 km/h (8.3 mph) |
| Standard dozer blade capacity (host) | 6.5 m3 (8.5 cu yd) |
| Standard dozer blade width (host) | 3.75 m (12.3 ft) |
Service capacities (summary)
| Fuel tank (host) | 450 L (118.9 gal) |
| Cooling system | 79.1 L (20.9 gal) |
| Engine oil / hydraulic system capacity | Not documented for this exact serial range — verify with your dealer |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
NT-855-1A(S/N 139838-UP) fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | Not confirmed for this exact engine/serial range in accessible sources. Cummins NT855-family industrial/genset variants list roughly 37-39 L (about 39-41 US qt) with filter change; this mechanical construction version may use a different pan depth. Verify against the host dozer's OMM lubrication chart before servicing. | Komatsu EO diesel engine oil (API CD/CE-class oil, correct for this mechanical, non-electronic engine generation). Viscosity is climate-split: SAE 30 or SAE 10W-30 in temperate ranges, SAE 15W-40 for wide seasonal swings. Confirm the exact viscosity-by-ambient-temperature chart in the OMM before topping off. |
| Cooling system (radiator, block, hoses) | 79 L (20.9 US gal) total system fill. | Komatsu genuine coolant (ethylene-glycol base, permanent-type antifreeze/anti-corrosion coolant), mixed per the ambient-temperature chart in the OMM. The engine block/jacket alone holds roughly 20-21 L of that total; the remainder sits in the radiator, hoses, and expansion tank. |
| Fuel tank | 450 L (118.9 US gal). | No. 2-D diesel fuel. This is a mechanical (non-ECM) engine of an older generation; no biodiesel blend or low-sulfur spec is called out for it specifically - use clean, water-free diesel per the OMM's fuel-quality section. |
| Transmission / steering-clutch case (direct-drive powertrain) | Not documented in accessible sources for this exact model/serial range. Consult the host dozer's OMM lubrication chart for the exact fill volume. | Komatsu TO powertrain oil, used across the direct-drive transmission, wet steering clutches, and brakes on this class of mechanical dozer. Grade is climate-split: TO10 for cold-weather operation, TO30 for warm climates, per the OMM's viscosity chart. |
| Final drives (each side) | Not documented in accessible sources for this exact model/serial range. Final drive fill is listed separately from the transmission case in the OMM; consult that chart for the per-side volume. | Komatsu TO powertrain oil, same specification as the transmission/steering-clutch case. |
| Hydraulic tank (blade lift/tilt/angle circuit) | Not documented in accessible sources for this exact model/serial range. Consult the host dozer's OMM lubrication chart. | Komatsu HO hydraulic oil is the standard call-out for this era, though some mechanical-dozer blade circuits of this vintage share oil with the powertrain (TO-series). Confirm which spec the OMM lists for this specific chassis before adding oil. |
| Axles/differentials | Not applicable. | Not applicable - this is a crawler dozer. Final drives take the place of axle differentials; there is no separate axle housing. |
| Grease points (pins, bushings, track/linkage) | Spec only - no reservoir capacity applies; service per grease-point interval in the OMM. | Komatsu genuine multipurpose lithium-based chassis grease (NLGI 2 grade) for pins, bushings, and track/linkage grease points. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Komatsu NT-855-1A(S/N 139838-UP) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
Servicing the NT-855-1A(S/N 139838-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
With no ECM or fault codes on the NT-855-1A, oil and coolant sampling do the early-warning work. Track coolant additive (SCA) level and watch engine oil for coolant intrusion, the first sign of the wet-sleeve liner cavitation pitting known on this engine. Sample TO powertrain oil at case drains to catch dual-pump aeration wear on the transmission/steering-clutch circuit before it shows up as a driveline complaint. Pair oil analysis with a periodic compression or leak-down check rather than relying on smoke color alone.
Corrective & Common Repairs
A plugged fuel tank vent is the top reported cause of this engine dying after 10-15 minutes of normal running — crack the fuel cap to confirm before chasing the PT pump or injectors. Clogged injector tips usually trace back to skipped fuel filter changes, not injector failure. On the D80/D85-18 driveline, aerated transmission or steering oil from the dual-pump Y-suction pipe calls for resealing both pumps, not just the one acting up, and a no-first-start-engagement after sitting is a known startup quirk to rule out before condemning the transmission.
Overhaul & Rebuild Points
Persistent white smoke at start-up or under load, plus excessive crankcase pressure at the oil breather, signals top-end wear worth a compression check before committing to a rebuild. Valve lash and PT injector timing must be set to this serial range's own clearance figures, not reused from another NT855 build, since governor settings and injector clearance vary by series. When liners come out, replace liner seals as a set — seal failure, not just liner pitting, is the usual root cause of coolant-in-oil contamination on this engine.
Seasonal & Environment Servicing
Long cranking and heavy smoke on cold starts are normal for this mechanical, relatively low-compression PT-injected engine; cold-climate fleets commonly add an ether-assist system rather than treat it as a fault. Split engine oil viscosity by season — lighter grades in temperate ranges, SAE 15W-40 for wide swings — and swap TO10 powertrain oil in cold weather for TO30 in warm climates per the OMM chart. Check the fuel tank vent more closely in cold weather, since condensation adds to the blockage risk that already causes stalling on this engine.
NT-855-1A(S/N 139838-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 07281-00197 | Clamp,(With Pre-Fuel Filter) | Fuel system service | Check fitment → |
| 6610-71-8004 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 6610-71-8005 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| 09019-08035 | Wrench,Filter (For Add. Fuel Filter) | Fuel system service | Check fitment → |
| 6128-81-7042 | Element Assembly, Air Cleaner | Air intake service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
All NT-855-1A(S/N 139838-UP) assemblies by section
Every catalogued assembly group for the Komatsu NT-855-1A(S/N 139838-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Cooling And Electrical Systems
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator (1.2kw? 50a) (Delco-Remy)
| 60***90 | Alternator A. (50a) | 1 |
| CU***71 | Resistor | 3 |
| CU***06 | Washer | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator (25a)(#139838-187609)
| 60***70 | Alternator A. (25a) | 1 |
| KD***37 | Bearing,Ball? Front | 1 |
| KD***20 | Holder,Brush | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator (35a)(#187610-)
| 60***60 | Alternator A. (35a) | 1 |
| KD***80 | Collar | 1 |
| KD***70 | Rear Bracket Ass'Y,Rear | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator (Sandy And Dusty Spec.) (25a)
| 60***71 | Alternator A. (25a) | 1 |
| KD***20 | Collar | 1 |
| KD***82 | Rotor Ass'Y | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator And Mounting
| 01***60 | Bolt, Trunnion Cap | 1 |
| 01***35 | Bolt,(Cold Weather Spec.) | 1 |
| 01***55 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Alternator And Mounting (1.2kw? 50a)
| 01***65 | Bolt, Mount Side Weights | 1 |
| 01***16 | Nut,(Balancer) | 1 |
| 01***19 | Washer,(Not Used With Ventilator) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Cooling Fan And Tension Pulley
| 01***16 | Bolt (Welded) | 4 |
| 01***20 | Bolt | 2 |
| 01***11 | Nut,(For Center Guard) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Corrosion Resistor
| 01***29 | Washer,Spring (Cold Weather Spec.) | 4 |
| 02***32 | Bolt,(With Joy Stick Steering) | 4 |
| 07***40 | Hose,See Fig. K4010-05a0 | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Hand Primer(#155814-)
| 66***01 | Hand Primer Ass'Y,Priming | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Regulator And Safety Relay
| 08***01 | Dust - Indicator | 1 |
| 60***10 | Regulator Ass'Y | 1 |
| 60***30 | Safety Relay A.,(A)(W/After Cooler)(S6d155-4b) | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Starting Motor (11kw)(#139838-187612)
| 60***24 | Starting Motor A.,(11kw) (Cold Weather Spec.) | 1 |
| KD***00 | Seal Ass'Y,(Not Shown) | 1 |
| KD***82 | Screw,Dish | 8 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Starting Motor (11kw)(#187613-194438)
| 60***60 | Starting Motor A.,(11kw) | 1 |
| SD***09 | Metal | 1 |
| SD***20 | O-Ring | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Starting Motor And Mounting (11kw)(#139838-187612)
| 01***22 | Screw | 2 |
| 01***45 | Screw | 3 |
| 01***29 | Washer,Spring (Cold Weather Spec.) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Starting Motor And Mounting (11kw)(#187613-)
| 01***45 | Bolt,(For Slag Handling) | 3 |
| 01***29 | Washer,Spring (Cold Weather Spec.) | 1 |
| 01***48 | Washer,Spring? Single Flange | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Water Pump
| 01***29 | Washer,Spring (Cold Weather Spec.) | 7 |
| 02***57 | Bolt | 5 |
| 02***83 | Bolt | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cooling And Electrical Systems : Water Pump Piping
| 01***11 | Nut,(With Under Mirror) | 2 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 1 |
| 01***29 | Washer,Spring (Cold Weather Spec.) | 4 |
Cylinder Block
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Cam Follower And Push Rod
| 02***25 | Bolt | 18 |
| 02***24 | Washer,Radio Controlled Slag Handling | 18 |
| 66***10 | Housing Ass'Y,Cam Follower | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Camshaft
| 02***25 | Key | 1 |
| 02***04 | Plug,(For Shipping) | 1 |
| 66***30 | Washer,Thrust | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Crankshaft And Vibration Damper
| 01***25 | Bolt - Rear Guard Mounting | 6 |
| 01***36 | Washer,Radio Controlled Slag Handling | 6 |
| 01***48 | Washer,Spring? Single Flange | 6 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Cylinder Block
| 02***16 | Bolt | 12 |
| 02***25 | Bolt,(Cold Weather Spec.) | 2 |
| 02***16 | Bolt | 6 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Engine Support
| 01***45 | Bolt | 8 |
| 66***31 | Plate,Lock (K5) | 4 |
| 66***10 | Bracket,R.H | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Flywheel And Flywheel Housing
| 01***30 | Bolt,Radio Controlled Slag Handling | 6 |
| 01***55 | Bolt,(For France Noise Suppression) | 4 |
| 01***36 | Washer,Radio Controlled Slag Handling | 6 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Gear Case Cover
| 02***25 | Bolt,(Cold Weather Spec.) | 3 |
| 02***51 | Bolt | 9 |
| 02***57 | Bolt | 8 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Oil Pan
| 01***30 | Bolt,(Cold Terrain Spec.) | 1 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***30 | Bolt,(For France Noise Suppression) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Piston And Connecting Rod
| 02***13 | Pin,Dowel | 2 |
| 66***30 | Ring,Snap | 2 |
| 67***21 | Piston Ring Ass'Y | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Power Take Off
| 01***35 | Bolt, Mounting - Flywheel Housing End | 5 |
| 01***40 | Bolt,(Dust And Dirt Protection) | 2 |
| 01***35 | Bolt,(For Pedal Steering) | 4 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Block : Rear Cover
| 02***16 | Bolt | 4 |
| 02***25 | Bolt | 2 |
| 02***32 | Bolt | 2 |
Cylinder Head
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Air Cleaner And Pre-Cleaner
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***35 | Bolt, Mounting - Flywheel Housing End | 2 |
| 01***45 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Air Cleaner And Pre-Cleaner (For Trimming Dozer) (Tunnel Spec.)
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***35 | Bolt, Mounting - Flywheel Housing End | 2 |
| 01***45 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Air Intake Manifold And Connection
| 01***25 | Bolt,(Without Auto Priming System) | 4 |
| 01***30 | Bolt,Radio Controlled Slag Handling | 2 |
| 01***35 | Bolt - Torque Converter Totransmission Mounting | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Cylinder Head
| 02***04 | Plug | 6 |
| 02***04 | Plug,(For Shipping) | 4 |
| 02***07 | Plug,(For Shipping) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Exhaust Manifold
| 01***45 | Screw | 4 |
| 01***50 | Bolt | 4 |
| 02***38 | Bolt | 8 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Muffler
| 01***30 | Bolt,(For France Noise Suppression) | 4 |
| 01***70 | Screw | 2 |
| 01***30 | Bolt | 4 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Rocker Arm And Housing
| 02***27 | Bolt,Radio Controlled Slag Handling | 2 |
| 02***78 | Bolt | 4 |
| 02***32 | Washer,Spring | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Rocker Arm Housing Cover
| 01***29 | Washer,Spring (Cold Weather Spec.) | 1 |
| 02***22 | Bolt | 1 |
| 02***22 | Bolt | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Thermostat
| 01***29 | Washer,Spring (Cold Weather Spec.) | 8 |
| 02***25 | Bolt,(Cold Weather Spec.) | 2 |
| 02***38 | Bolt,Radio Controlled Slag Handling | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Turbocharger
| 02***16 | Bolt | 16 |
| 02***20 | Washer,Radio Controlled Slag Handling | 4 |
| 02***16 | Washer,Radio Controlled Slag Handling | 16 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Cylinder Head : Water Manifold
| 01***29 | Washer, Spring | 12 |
| 02***32 | Bolt,(With Joy Stick Steering) | 12 |
| 02***07 | Plug,(For Shipping) | 1 |
Fuel System
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Fuel Filter(#139838-155378)
| 01***12 | Bolt (M8-1.25x12) | 1 |
| 01***40 | Bolt,(For Position Fixing) | 2 |
| 04***12 | Wire,Lock | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Fuel Filter(#155379-)
| 01***29 | Washer,Spring (Cold Weather Spec.) | 4 |
| 02***32 | Bolt,(With Joy Stick Steering) | 4 |
| 02***25 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Injection And Fuel Connection
| 67***20 | Plunger Ass'Y | 1 |
| 67***31 | Plunger Ass'Y | 1 |
| 67***10 | Adapter,Injector | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (1/7)
| 02***04 | Nut | 2 |
| 02***04 | Plug | 4 |
| 02***18 | O-Ring,Filter | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (2/7)
| 01***20 | Washer,Spring | 3 |
| 02***25 | Bolt,Radio Controlled Slag Handling | 2 |
| 02***04 | Nut | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (3/7)
| 01***13 | Washer,(For Alternator 50a) | 2 |
| 01***20 | Washer,Spring | 8 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (4/7)
| 01***20 | Washer,Spring | 4 |
| 02***32 | Bolt,(Logging Spec.) | 2 |
| 66***20 | Ring,Snap | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (5/7)
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (6/7)
| 01***20 | Washer,Spring | 5 |
| 02***32 | Bolt,(Logging Spec.) | 3 |
| 02***38 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump (7/7)
| 01***20 | Washer,Spring | 2 |
| 02***32 | Bolt,(Logging Spec.) | 2 |
| 02***57 | Bolt | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump And Piping(#139838-155378)
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 1 |
| 01***08 | Nut, Regular Hexagon (M10-1.50) | 1 |
| 01***18 | Nut | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump And Piping(#155379-)
| 01***20 | Bolt | 1 |
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 2 |
| 01***19 | Washer,(Not Used With Ventilator) | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Pt Fuel Pump Drive
| 02***25 | Bolt | 5 |
| 02***28 | Washer,Spring | 5 |
| 02***19 | Key | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Water Separator And Piping(#155379-)
| 01***30 | Bolt,(For France Noise Suppression) | 2 |
| 01***35 | Bolt, Mounting - Flywheel Housing End | 4 |
| 01***08 | Nut, Regular Hexagon (M10-1.50) | 2 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Fuel System : Water Separator(#155379-)
| 07***75 | O-Ring,Steering Oil Filter | 1 |
| 07***12 | Gasket,Mechanical Pump Piping | 1 |
| 60***60 | Plug,Drain (For Pakistan) | 1 |
Lubricating Oil System
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Lubricating Oil Bypass Filter
| 02***32 | Bolt | 2 |
| 02***20 | Washer,Spring | 2 |
| 02***01 | O-Ring (Kit) | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Lubricating Oil Cooler (Main Clutch)
| 01***29 | Washer,Spring (Cold Weather Spec.) | 24 |
| 01***38 | Washer,Radio Controlled Slag Handling | 2 |
| 01***16 | Washer,Radio Controlled Slag Handling | 4 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Lubricating Oil Cooler And Oil Filter
| 01***25 | Bolt,(Sandy? Dusty Terrain Spec.) | 3 |
| 01***29 | Washer,Spring (Cold Weather Spec.) | 7 |
| 01***30 | Washer,Spring(Sandy?Dusty Terrain S.) | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Lubricating Oil Piping
| 01***16 | Bolt,(For Slag Handling) | 1 |
| 01***16 | Bolt,(Sandy And Dusty Spec.) | 1 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Lubricating Oil Pump
| 02***83 | Bolt | 6 |
| 02***95 | Bolt | 1 |
| 02***22 | Bolt | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : P.T.O. Lubricating Oil Piping
| 01***30 | Bolt,(For France Noise Suppression) | 4 |
| 01***30 | Washer,Spring(Sandy?Dusty Terrain S.) | 4 |
| 07***15 | Gasket,(Hd325?Pc750?800?1800) (A5010) | 3 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Lubricating Oil System : Turbocharger Lubricating Oil Piping
| 01***16 | Bolt,(For Slag Handling) | 1 |
| 01***25 | Washer,Spring?(Sandy And Dusty Spec.) | 1 |
| 07***10 | Hose | 1 |
Tool And Kit
Komatsu : Nt-855-1a(S/N 139838-Up) : Tool And Kit : Gasket Kit
| 01***23 | Washer,(Not Shown) | 1 |
| 02***07 | O-Ring (K6) | 1 |
| 02***18 | O-Ring,Filter | 1 |
Komatsu : Nt-855-1a(S/N 139838-Up) : Tool And Kit : Tool
| 09***35 | Wrench,Filter (For Add. Fuel Filter) | 1 |
| 09***11 | Wrench | 1 |
| 09***14 | Wrench | 1 |
Frequently asked questions
What engine powers this part?
The Cummins NT-855-1A, a turbocharged mechanical diesel — 14.0 L (855 cu in), inline six-cylinder, PT fuel injection, no aftercooling, no electronic controls. It is rated around 164 kW (220 hp) at 1800 rpm with roughly 1,029 Nm (759 lb-ft) max torque.
What is the operating weight of the machine this engine powers?
It varies by drivetrain configuration. The power-shift A-series host runs roughly 23,310-23,610 kg (51,390-52,051 lb); the lighter direct-drive E-series host runs roughly 19,000-19,300 kg (41,900-42,560 lb).
What replaced this engine?
The NT-855-1A itself succeeded the naturally aspirated NH-220-CI engine used on the earlier D80A-12/D85A-12 dozer generation. Which engine directly replaced the NT-855-1A on later D80/D85 dozer generations is not confirmed in available records — check with your dealer for the exact direct-replacement crossover.
What NT-855-1A(S/N 139838-UP) owners discuss
What wear patterns show up most often on the NT855-1A's mechanical top end and cylinder liners?
Operators and rebuild shops report the same two wear points on this Cummins wet-sleeve six: cam lobe wear from the mechanical injector lifters, and cylinder liner pitting on the coolant side caused by cavitation from combustion vibration. Liner pitting starts as microscopic pits and, left unchecked, can turn into pinholes that let coolant seep into the combustion chamber with little or no visible smoke at first. Because this engine has no electronic monitoring, the only way to catch it early is periodic coolant additive testing and a compression or leak-down check at oil changes.
Why does an NT855-1A sometimes run fine for 10-15 minutes and then die?
The most frequently reported stalling pattern on the mechanical PT fuel system is a plugged fuel tank vent. Once the vent clogs, the low-pressure gear pump starves for supply and the engine runs normally until tank vacuum builds enough to cut fuel flow, then it shuts down abruptly. It restarts and repeats the cycle. Owners narrow this down by cracking the fuel cap after a stall; if the engine picks back up, the vent is the culprit rather than the injectors or the PT pump itself.
What causes hard cold starts and white or black smoke on start-up?
Long cranking and heavy smoke on cold starts are typical of this mechanical, relatively low-compression PT-injected engine and are not automatically a sign of trouble. Fleets running these dozers in cold climates commonly add an ether-assist system rather than treat it as a fault. Persistent misfiring with alternating white and black smoke after warm-up, though, points to a clogged injector tip, usually traced back to skipped fuel filter changes rather than a problem with the engine itself.
How often does the PT injection system need attention, and can an owner adjust it?
The PT gear-pump-and-injector system needs periodic injector and governor adjustment to hold correct idle and full-throttle fuel settings, and owners with the right gauge sets do perform this in the field. Because rocker and injector clearance figures and governor settings vary by series and directly affect fuel delivery and engine load limits, pull the exact clearance and torque figures for this serial range from the service manual rather than reusing a number from a different NT855 build, and have your dealer verify the adjustment on a running engine before returning it to work.
What's the typical driveline complaint on the D80/D85-18 chassis this engine is fitted to?
The recurring complaint on this chassis is aerated transmission or steering oil traced to the dual-pump Y-style suction pipe: one pump can lose prime if a suction-side seal or o-ring on either pump starts leaking air, and the fix reported by shops is resealing both pumps rather than just the one that's acting up. A second common pattern is the machine not going into gear on the first start after sitting off for more than about 10 minutes, then engaging normally on a restart; operators treat this as a known startup quirk to check for rather than a transmission failure.
Does the NT855-1A throw electrical fault codes or have sensor-driven diagnostics?
No. This is a fully mechanical PT-injected engine with no ECM, so there is nothing resembling a modern fault code list. What owners actually deal with on the electrical side is basic charging and starting circuit wear: alternator output, starter solenoid contacts, and gauge sender accuracy for oil pressure and coolant temperature. Diagnosis on this engine leans on those gauges plus exhaust smoke color and sound rather than any electronic sensor.
What should a buyer check before purchasing a used NT855-1A powered D80/D85-18?
Pull the engine oil breather cap and look for oil blowing out or excessive crankcase pressure, and watch the exhaust for white smoke at start-up and under load, both flagged by used-equipment buyers as signs the engine may need a top-end or full rebuild. Check engine oil, coolant, and power-train case oil levels and condition together, since a coolant-in-oil mix points at liner seal failure from past overheating. Cycle the transmission from cold and again after it sits, to catch the known delayed gear-engagement quirk, and inspect track shoe wear against the ground conditions the machine worked in. Because internal engine condition can't be fully judged by eye, have your dealer verify compression and blow-by before you commit to a purchase.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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