Mitsubishi K4F Specifications
| Engine Model: Mitsubishi K4F |
| Engine Type: 4-cycle inline 4-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 96.4 cu.in (1.58 L) |
| Rated Engine Power: 35 Hp (26 kW) at 2500 rpm |
| Fuel System Type: Indirect injection |
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The Mitsubishi K4F is a 1.6-liter, naturally
aspirated inline-four diesel engine produced by Mitsubishi Motors as
part of the K-series engine family. This engine was developed during the
1980s as a compact, fuel-efficient powerplant for mid-sized compact
tractors, skid-steer loaders, excavators, and various industrial
machinery applications. The K4F features a vertical, water-cooled layout
with a swirl chamber indirect injection system, a design that
prioritizes smooth operation and low noise over high power output.
The engine gained widespread recognition in agricultural equipment,
powering Mitsubishi tractor models such as the MT25 and MT30. The
industrial variant found application in wheel loaders, compact
excavators, and Deutz-Fahr tractors. The Mitsubishi K4F is known for its
serviceability, featuring a robust cast iron construction with
replaceable components that support in-frame overhaul capability.
Engine Type: Inline-4, four-stroke, vertical, water-cooled diesel.
Displacement: 1,580 cc (1.58 L / 96.4 cu.in).
Bore and Stroke: 78.0 mm x 82.6 mm (3.07 in x 3.25 in).
Compression Ratio: 22.0:1.
Combustion System: Swirl chamber, indirect injection.
Firing Order: 1-3-4-2.
Rated Power Output: 30-35 hp (22-26 kW).
Compression Pressure (Standard): 30 kg/cm2 (427 psi) at 280 rpm.
Injection Timing: 21 degrees before top dead center (BTDC).
The cylinder block is constructed from cast iron, a material selection
providing the rigidity and vibration damping required for sustained
diesel operation in agricultural and industrial environments. This
contrasts with the aluminum blocks used in some petrol variants of
Mitsubishi K-series engines, which were designed for light passenger
vehicles where weight reduction was prioritized over structural mass.
The block incorporates five main bearing bulkheads supporting a forged
steel crankshaft with precision-engineered counterweights to reduce
lateral forces and enhance engine stability during high-speed operation.
The Mitsubishi K4F engine block features a replaceable wet-type cylinder
liner design, a significant advantage for agricultural equipment where
downtime directly impacts productivity. This design permits complete
engine overhaul without removing the engine from the equipment frame, as
the liners can be extracted and replaced while the block remains
installed.
The block includes cast water jacket passages surrounding each cylinder
liner for uniform coolant distribution and thermal management. The oil
sump is a pressed steel or cast aluminum component with a capacity
appropriate to the specific chassis configuration, varying between 4.5
and 5.0 liters depending on the oil pan design for each equipment
application. The block features integral mounting flanges that provide
attachment points for tractor or industrial equipment frames.
The cylinder head is a single-piece cast iron unit that houses the swirl
chamber pre-combustion system for each cylinder. The swirl chamber
design promotes thorough mixing of fuel and air before combustion
propagates into the main cylinder, contributing to smooth operation and
reduced combustion noise. This indirect injection layout is
characteristic of diesel engines from this era, providing quieter
operation than direct injection designs at the cost of slightly reduced
fuel efficiency.
The valvetrain operates on an overhead valve (OHV) configuration with
pushrods and rocker arms. The camshaft is located within the cylinder
block and driven by a gear train from the crankshaft. Each cylinder
receives two valves: one intake and one exhaust. Valve seat inserts are
pressed into the cylinder head and machined to precise angles for
positive sealing against diesel combustion pressures. The engine uses
mechanical valve lifters with screw-and-locknut adjusters for manual
valve clearance setting. The valve cover is a steel stamping sealed by a
gasket.
The fuel system employs a mechanical indirect injection design. The
injection pump is a Bosch M-type distributor pump mounted on the side of
the cylinder block and driven by a gear from the camshaft. The pump
incorporates a mechanical governor that maintains engine speed under
varying loads, a critical feature for PTO-driven agricultural implements
where consistent rotational speed is required for proper implement
operation. The pump uses throttle-type nozzles that deliver fuel in a
precisely directed spray pattern into each swirl chamber.
High-pressure injection lines carry fuel from the distributor pump to
individual injectors mounted in the cylinder head. Injector opening
pressure is calibrated to specifications, ensuring proper atomization of
fuel for complete combustion. A fuel filter with an integrated water
separator is mounted between the fuel tank and the injection pump. This
water separator is essential for diesel engines, as water contamination
from fuel storage can cause corrosion and premature wear of the
precision injection pump components. A hand-priming pump is provided on
the filter housing or injection pump for bleeding air from the system
after filter changes.
The lubrication system is a fully pressurized, forced lubrication design
using a trochoid-type oil pump. The pump is mounted inside the oil pan
or on the front of the engine block and driven by the crankshaft or
camshaft gear train. The trochoid pump design consists of an inner rotor
with lobes that mesh with an outer rotor, creating expanding and
contracting chambers that draw and discharge oil with minimal pulsation.
The pump draws oil through a screened pickup tube positioned at the
lowest point of the oil pan to maintain suction even when the equipment
operates on inclines.
The full-flow spin-on oil filter is mounted on the cylinder block. As
all oil circulated by the pump passes through this filter before
reaching the bearing surfaces, any contaminants are removed from the
lubrication circuit during every pass. From the filter, oil circulates
through main oil galleries drilled longitudinally through the block,
supplying the crankshaft main bearings, connecting rod bearings,
camshaft bearings, and the valve train components through external or
internal passages.
The cooling system is a pressurized, thermostatically controlled liquid
cooling setup with a belt-driven centrifugal water pump. Coolant
circulates from the radiator lower tank through the water pump, into the
cylinder block water jacket, upward through the cylinder head, and
returns to the radiator upper tank through a cast outlet at the front or
rear of the cylinder head. The system incorporates a wax-type thermostat
with a nominal opening temperature that maintains engine operating
temperature within the designed range, allowing the engine to reach
optimal thermal efficiency quickly while preventing overheating under
sustained load.
Coolant capacity for the engine block only is 4.0 L (4.2 US qt), with
additional volume required for the radiator and connecting hoses. The
total system capacity depends on the specific equipment application and
radiator size. A belt-driven fan, mounted on the water pump hub and
enclosed in a fan shroud, draws air through the radiator core to remove
heat from the circulating coolant. The cooling system is pressurized by
a radiator cap with a pressure relief valve, raising the boiling point
of the coolant for operation under load.
Electrical System: The engine uses a 12-volt electrical system with
negative ground. A 12-volt, 1.6 kW or 2.0 kW starter motor engages the
flywheel ring gear for engine cranking. A 12-volt, 35-ampere alternator
supplies charging current to the battery and powers the electrical loads
during engine operation.
Timing System: The camshaft is driven by a gear train at the front of
the engine. This gear drive system provides precise timing without the
maintenance or replacement concerns associated with belt or chain
drives, contributing to the engine's reputation for reliability.
Air Intake System: A dry-type air cleaner with a replaceable paper
filter element is mounted on the intake side of the engine. Agricultural
and construction equipment often uses a dual-element air cleaner with a
primary filter and a secondary safety filter to protect the engine in
dusty operating environments.
Governor System: The mechanical governor is integrated into the
injection pump housing. A flyweight mechanism senses engine speed and
adjusts the fuel control rack position to maintain the selected engine
speed regardless of load variations.
Overall length from the front cover to the flywheel housing mounting
face is 750 mm (29.5 in). Width, measured across the cylinder head and
injection pump, is 550 mm (21.7 in). Height from the oil pan rail to the
top of the valve cover is 650 mm (25.6 in). The complete engine dry
weight, including the intake and exhaust manifolds, injection pump,
injectors, starter motor, alternator, water pump, and flywheel, is 180
kg (397 lb). The cast iron cylinder block and cylinder head contribute
the majority of this mass.
Engine Oil Capacity: With filter change, 4.5-5.0 L (4.8-5.3 US qt),
depending on the specific oil pan configuration and equipment
application. Recommended Oil Viscosity: 15W-40 for temperate climates,
meeting API classification CD or higher for diesel service. Oil Change
Interval: 250-500 operating hours, depending on service conditions.
Severe service in dusty environments requires more frequent changes.
Fuel Filter Replacement Interval: 250-500 operating hours. Glow Plug
Operation: Pre-heat for 5-10 seconds before starting in cold conditions.
Coolant Capacity: Engine block only, 4.0 L (4.2 US qt). Total system
capacity including radiator depends on the application. Coolant Type:
Ethylene glycol antifreeze for diesel engines with supplemental coolant
additives (SCAs) for wet liner protection. Thermostat Opening
Temperature: 82°C (180°F). Air Filter Replacement Interval: 100-250
operating hours in dusty agricultural environments, longer under clean
conditions. Injection Timing: 21 degrees BTDC. Idle Speed: 650-750 rpm
in neutral.
Valve Clearance Adjustment (Cold Engine): Intake and Exhaust: 0.25 mm
(0.010 in). Valve Clearance Adjustment Interval: Every 500-1,000
operating hours or as indicated by increased engine noise. Compression
Pressure (Standard): 30 kg/cm2 (427 psi) at 280 rpm. Compression
Pressure (Service Limit): Consult the engine manual for minimum
acceptable compression pressure. Injector Inspection Interval: Every
1,000 operating hours. Injection Pump Service: Consult the engine manual
for timing procedures, which involve shim adjustments on the pump
mounting flange.
Cylinder Head Bolts (M12): 87-94 lb-ft (118-127 Nm).
Cylinder Head Bolts (M10): 58-65 lb-ft (78-88 Nm).
Connecting Rod Cap Nuts: 36-40 lb-ft (49-54 Nm).
Main Bearing Cap Bolts: 72.3-79.5 lb-ft (98-108 Nm).
Flywheel Bolts: 61.5 ± 3.6 lb-ft (83 ± 5 Nm).
Crankshaft Pulley Bolt: 150-180 lb-ft (203-244 Nm).
Injector Hold-Down Clamp Bolts: 18-22 lb-ft (24-30 Nm).
Injection Pump Mounting Nuts: 20-25 lb-ft (27-34 Nm).
Glow Plug Torque: 12-15 lb-ft (16-20 Nm). Do not overtighten.
Rocker Arm Shaft Bracket Bolts: 25-30 lb-ft (34-41 Nm).
Camshaft Thrust Plate Bolts: 18-22 lb-ft (24-30 Nm).
Intake Manifold Nuts: 25-30 lb-ft (34-41 Nm).
Exhaust Manifold Nuts: 25-30 lb-ft (34-41 Nm).
Oil Pan Bolts: 12-15 lb-ft (16-20 Nm).
Valve Cover Bolts: 6-8 lb-ft (8-11 Nm).
Water Pump Mounting Bolts: 14-18 lb-ft (19-24 Nm).
Starter Motor Mounting Bolts: 28-35 lb-ft (38-47 Nm).
Alternator Mounting Bolts: 28-35 lb-ft (38-47 Nm).
The Mitsubishi K4F engine was installed in agricultural, construction,
and industrial equipment across multiple markets from approximately the
mid-1980s through the 1990s.
Mitsubishi MT25 Compact Tractor: A 25-horsepower class tractor using the
K4F engine for general agricultural duties including mowing, tilling,
and light loader work.
Mitsubishi MT30 Compact Tractor: The 30-horsepower variant of the MT
series, using the K4F engine for heavier tasks such as rotary tilling
and material handling.
Mitsubishi MT33 Compact Tractor: A higher-output configuration of the
same tractor platform, representing the upper end of the K4F power
range.
Mitsubishi W5200A Wheel Loader: The industrial variant of the K4F,
designated K4F-DT or K4F-T, powered this compact wheel loader for
construction and material handling applications.
Deutz-Fahr AgroKid 35A Tractor: K4F-powered compact tractor sold under
the Deutz-Fahr brand, a common arrangement in European markets where
Deutz-Fahr distributed Mitsubishi-built tractors.
Deutz-Fahr AgroKid 45A Tractor: The larger variant of the AgroKid series
using the K4F engine for agricultural and estate maintenance duties.
Mitsubishi Compact Excavators: Various small excavator models used the
K4F engine for hydraulic power generation in construction and
landscaping applications.
Industrial Power Units: The K4F was offered as a stationary power unit
for generators, irrigation pumps, and other equipment requiring reliable
diesel power in a compact package.
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