Mitsubishi 4M40T Specifications
| Engine Model: Mitsubishi 4M40T |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve turbocharger liquid-cooled diesel |
| Total Displacement: 173 cu.in (2.83 L) |
| Rated Engine Power: 125-140 Hp (92-103 kW) at 4000 rpm |
| Fuel System Type: Direct injection |
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The Mitsubishi 4M40T is a 2.8-liter, inline-four,
turbocharged diesel engine introduced as the successor to the 4D56 family.
Launched in the mid-1990s, it was engineered to provide increased durability,
reduced noise and vibration, and enhanced torque delivery for heavier
applications. Unlike its predecessor, the 4M40T employs a timing chain instead
of a belt, significantly improving longevity and reliability under severe
operating conditions.
The engine became the cornerstone powertrain for the second-generation
Mitsubishi Pajero (Montero), the L200 Triton pickup, the Delica L400 van, and
light-duty Canter trucks. Its robust cast-iron construction, combined with an
intercooled turbocharger, established it as one of Mitsubishi’s most dependable
diesel powerplants throughout the late 1990s and 2000s.
The 4M40T is a 4-stroke, inline 4-cylinder, water-cooled diesel engine utilizing
a single overhead camshaft (SOHC) valvetrain. Total displacement measures 2.835
Liters (2,835 cc / 173.0 cu.in), derived from a bore and stroke of 95.0 mm
(3.740 in) x 100.0 mm (3.937 in). The compression ratio is set at 21.0:1. The
firing order follows 1-3-4-2. Induction is provided by a turbocharger coupled
with an air-to-air intercooler.
Maximum power output ranges from 125 to 140 HP (92-103 kW) at 4,000 RPM, while
peak torque is delivered between 294 and 314 Nm (217-232 lb-ft) at 2,000 RPM.
Compression pressure standard is 3.0 MPa (440 psi), with a minimum service limit
of 2.2 MPa (320 psi). The dry weight of the engine is approximately 220 kg (485
lbs).
The cylinder block is constructed from cast iron using
a deep-skirt design that extends below the crankshaft centerline, providing
exceptional rigidity for the rotating assembly. The block features siamese bores
with a finished bore diameter of 95.0 mm (3.740 in). A distinguishing
characteristic of the 4M40T is the integration of a balance shaft system - a
twin-shaft assembly located within the crankcase - that operates at twice
crankshaft speed to cancel the secondary vibrations inherent in
large-displacement inline-four diesel engines.
The crankshaft is forged steel with induction-hardened journals and is supported
by five main bearings. Piston cooling jets (oil squirters) are cast into the
block structure, directing oil to the underside of each piston crown to manage
thermal loads under sustained turbocharged operation. The timing chain housing
is integrated into the front of the block, representing a structural departure
from the belt-driven architecture of earlier Mitsubishi diesel engines.
The cylinder head is manufactured from cast iron to
maintain thermal stability and gasket sealing integrity under the elevated
cylinder pressures generated by turbocharged operation. It employs a SOHC
configuration operating two valves per cylinder - one intake and one exhaust -
for a total of eight valves. The valves are arranged in a cross-flow pattern to
optimize swirl generation and combustion efficiency within the indirect
injection system.
The combustion chamber utilizes a swirl-type pre-combustion chamber design,
where fuel is injected into a turbulent air mass before combustion propagates
into the main cylinder. Valve clearance adjustment is performed via threaded
tappets located between the camshaft lobes and valve stems. Cold valve
clearances are specified as 0.20 mm (0.008 in) for intake valves and 0.30 mm
(0.012 in) for exhaust valves. The camshaft is driven by a single-row roller
timing chain equipped with a hydraulic tensioner that maintains optimal chain
tension throughout the engine’s service life.
The fuel system employs an inline injection pump - a
Bosch VE-type distributor pump or a Zexel equivalent - mounted to the cylinder
head side and driven directly by the timing chain. This pump delivers diesel
fuel to the swirl chambers at pressures calibrated to match the indirect
injection combustion characteristics. Fuel delivery is controlled by a
mechanical governor that responds to throttle input and engine load. The
injection pump incorporates a cold-start advance mechanism that modifies
injection timing during engine warm-up to improve cold drivability.
Glow plugs are installed in the cylinder head to pre-heat the swirl chambers for
cold starting. Depending on the market and application, the system utilizes
either a standard 12V glow plug configuration or a high-speed glow system that
reduces pre-heat times to approximately 2-3 seconds. A fuel injection nozzle
with a multi-hole configuration is installed in each cylinder, delivering fuel
directly into the swirl chamber.
Lubrication is provided by a gear-type oil pump driven
by the crankshaft, circulating oil through a full-flow filtration system. The
total oil capacity, including the filter and the oil cooler circuit, ranges from
6.5 to 7.5 Liters (6.9-7.9 qt). A critical feature of the 4M40T lubrication
system is the inclusion of piston cooling jets - precision nozzles mounted in
the crankcase that direct a continuous stream of engine oil to the piston
crowns. This system is essential for maintaining piston integrity under the
thermal load generated by the turbocharger and intercooler configuration.
The engine is equipped with a water-cooled oil cooler mounted adjacent to the
oil filter housing, which stabilizes oil temperature during sustained high-load
operation. Oil pressure is regulated by a relief valve set to maintain
consistent pressure across the operating range. The recommended oil viscosity is
15W-40 meeting API CF-4 or higher specifications.
The cooling system is a water-cooled, pressurized
design utilizing a centrifugal water pump driven by the serpentine accessory
belt. Coolant circulates through the cast-iron block and cylinder head, with
dedicated passages directing flow to the turbocharger bearing housing for
thermal protection. The system includes a bypass circuit that allows coolant to
circulate through the engine block during warm-up until the thermostat reaches
its opening temperature.
The thermostat is calibrated to maintain operating temperatures between 76°C and
82°C (169°F-180°F) under normal conditions. A large-capacity aluminum radiator
with a dual-electric fan configuration manages heat rejection for the engine and
the air-to-air intercooler. The intercooler is mounted in front of the radiator
and receives its own airflow path to reduce intake air temperature before it
enters the combustion chamber, a critical factor for maintaining power output
and controlling combustion temperatures under boost.
Turbocharger System: The engine is equipped with a
single, wastegated turbocharger mounted to a cast-iron exhaust manifold. The
turbocharger features a water-cooled bearing housing to prevent oil coking after
engine shutdown. Boost pressure is controlled by an actuator that opens the
wastegate to divert exhaust gases once the calibrated boost threshold is
reached. Intercooling is achieved through an air-to-air cooler mounted in the
front grille area, which reduces charge air temperature before delivery to the
intake manifold.
Timing System: The timing chain is a single-row roller chain driving the
camshaft, injection pump, and balance shaft assembly. A hydraulic tensioner
supplied by engine oil pressure maintains consistent chain tension, eliminating
the need for manual adjustments. The chain guides are constructed from high-wear
polymer materials and are designed to last the engine’s service life under
normal operating conditions.
Balance Shaft System: Two balance shafts are housed within the cylinder block,
rotating in opposite directions at twice the engine speed. These shafts are
gear-driven from the crankshaft and are phased to generate a vibration that
counteracts the secondary shaking forces of the inline-four engine
configuration. This system significantly reduces perceived vibration in the
vehicle cabin.
Starting System: The engine utilizes a reduction-gear starter motor with high
torque output for cold-start reliability. The glow plug system integrates a
controller that manages pre-glow duration, after-glow cycling to reduce white
smoke, and post-glow operation to stabilize idle quality after cold starts.
Length measured from the timing cover front face to the
flywheel housing mounting surface is 700 mm (27.6 in). Width across the valve
cover, injection pump, and turbocharger assembly measures 600 mm (23.6 in).
Height from the oil pan bottom surface to the top of the cylinder head cover is
780 mm (30.7 in). The dry weight of the fully dressed engine - including the
injection pump, turbocharger, intercooler piping, and all manifolds - is 220 kg
(485 lbs).
Regular maintenance is critical for the longevity of
the 4M40T. The timing chain does not have a mandatory replacement interval but
should be inspected for elongation and guide wear every 100,000 km (60,000
miles). Engine oil and filter changes are recommended at 5,000-7,500 km
(3,000-4,500 miles) under normal driving conditions, using diesel-rated oil
meeting the appropriate viscosity and API specifications.
Valve clearance inspections are scheduled every 40,000 km (25,000 miles), with
cold adjustments made to the specified intake clearance of 0.20 mm (0.008 in)
and exhaust clearance of 0.30 mm (0.012 in). The fuel filter should be replaced
annually or every 20,000 km (12,000 miles) to protect the injection pump from
water and particulate contamination.
Coolant replacement is recommended every two years or 40,000 km (25,000 miles)
to maintain corrosion inhibitor effectiveness. Compression pressure testing
should yield a standard value of 3.0 MPa (440 psi), with a minimum service limit
of 2.2 MPa (320 psi) and a maximum variation between cylinders of 0.2 MPa (30
psi). The glow plug system should be tested at each major service interval to
ensure proper cold-start function.
Cylinder Head Bolts (Cold), Step 1: 100 Nm (74 lb-ft).
Cylinder Head Bolts (Cold), Step 2: 50 Nm (37 lb-ft).
Main Bearing Cap Bolts: 20 Nm (15 lb-ft).
Connecting Rod Cap Bolts: 50 Nm (37 lb-ft).
Flywheel Bolts: 120-125 Nm (89-92 lb-ft).
Camshaft Sprocket Bolt: 80-90 Nm (59-66 lb-ft).
Rocker Arm Shaft Bolts: 30-35 Nm (22-26 lb-ft).
Injection Pump Drive Gear Bolt: 50-60 Nm (37-44 lb-ft).
Balance Shaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft).
Timing Chain Tensioner Bolts: 25-30 Nm (18-22 lb-ft).
Timing Chain Guide Bolts: 20-25 Nm (15-18 lb-ft).
Oil Pan Bolts: 10-12 Nm (7-9 lb-ft).
Water Pump Bolts: 20-25 Nm (15-18 lb-ft).
Glow Plug Installation: 15-20 Nm (11-15 lb-ft).
Turbocharger Mounting Nuts: 40-45 Nm (30-33 lb-ft).
Exhaust Manifold Nuts: 25-30 Nm (18-22 lb-ft).
Intake Manifold Bolts: 20-25 Nm (15-18 lb-ft).
Valve Cover Bolts: 8-10 Nm (71-89 lb-in).
Engine Mount Bracket Bolts: 55-65 Nm (41-48 lb-ft).
The Mitsubishi 4M40T served as a primary diesel
powertrain across a wide range of Mitsubishi vehicles and light commercial
platforms throughout the late 1990s and into the 2000s.
Key applications include:
Mitsubishi Pajero / Montero (V25, V26, V45, V46): Second-generation models
produced from 1994 through 1999. The 4M40T was offered in both intercooled and
non-intercooled configurations depending on market and trim level, with the
intercooled variant reserved for higher-specification models.
Mitsubishi L200 / Triton / Strada (K74, K75, K76): Third-generation pickup
trucks manufactured between 1996 and 2005. The engine provided the torque
necessary for load-carrying applications while maintaining durability in
commercial use.
Mitsubishi Delica / L400 (V45, V46): Fourth-generation van and passenger wagon
variants produced from 1994 through 2004. The 4M40T was the preferred diesel
option for the Delica Space Gear series, valued for its combination of power and
refinement in a compact engine bay.
Mitsubishi Canter / FE Series: Light-duty truck applications where the 4M40T was
installed in cab-over configurations for commercial delivery vehicles requiring
robust low-end torque and extended service intervals.
Hyundai Galloper: The Korean-manufactured Galloper SUV, produced under license
from Mitsubishi, utilized the 4M40T as its diesel powertrain option in later
production years, continuing the engine’s legacy beyond Mitsubishi’s own
production timeline.
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