Mercedes-Benz OM616 Specifications
| Engine Model: Mercedes-Benz OM616 |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled diesel |
| Total Displacement: 146.4 cu.in (2.39 L) |
| Rated Engine Power: 64-90 Hp (48-67 kW) at 4200 rpm |
| Fuel System Type: Indirect injection |
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The Mercedes-Benz OM616 is a naturally aspirated diesel
engine produced between 1973 and 1985, with licensed production continuing in
other markets well into the 2010s. As one of the most durable diesel engines in
automotive history, the OM616 succeeded the OM615 and served as the
four-cylinder foundation for the five-cylinder OM617. The engine is
characterized by its heavy cast iron construction, indirect injection with a
pre-chamber design, and a mechanical Bosch injection pump.
The OM616 requires no electrical input for operation once started, relying
entirely on mechanical fuel delivery and governor systems. Its reputation for
longevity - frequently exceeding 500,000 km (310,000 miles) with basic
maintenance - established the engine as a benchmark for durability in passenger
car and light commercial applications.
Engine Type: Inline 4-cylinder, 4-cycle, water-cooled, naturally aspirated
diesel.
Displacement: 2,399 (146.4 cu.in) depending on bore variation.
Bore: 90.9 mm (3.58 in).
Stroke: 92.4 mm (3.64 in) for all variants.
Compression Ratio: 21.0:1 for early variants.
Compression Ratio: 22.0:1 for late variants with revised pre-chamber design.
Valvetrain Configuration: Single Overhead Camshaft, 8 valves (2 valves per
cylinder).
The camshaft is driven by a duplex (double-row) timing chain.
Firing Order: 1-3-4-2.
Maximum Power
Early variants (1973-1978): 64 hp (48 kW) @ 4,200 rpm.
Late variants (1978-1985): 71 hp (53 kW) @ 4,400 rpm.
Licensed turbocharged variants (Force Motors, India): 90 hp (67 kW) @ 4,000 rpm.
Maximum Torque
All naturally aspirated variants: 137 Nm (101 lb-ft) @ 2,400 rpm.
Licensed turbocharged variants: 186 Nm (137 lb-ft) @ 1,800-2,200 rpm.
The cylinder block is manufactured from cast iron with
a deep-skirt design extending below the crankshaft centerline. This construction
provides exceptional rigidity and resistance to thermal distortion. Bore
diameter measures 90.9 mm (3.58 in) for late variants and 91.0 mm (3.58 in) for
early variants. The block features a closed-deck design with pressed-in cast
iron cylinder liners that are replaceable during major overhauls.
The crankshaft is forged steel with eight counterweights, supported by five main
bearings. The block incorporates an integrated oil gallery system feeding the
main bearings, connecting rods, and camshaft bearings. A large oil sump with a
capacity of 6.5 liters (6.9 qt) contributes to thermal stability and extended
oil change intervals.
The cylinder head is manufactured from cast iron,
matching the block material to ensure uniform thermal expansion.
Valves: 8 total; 4 intake, 4 exhaust.
Intake Valve Diameter: 40.0 mm (1.57 in).
Exhaust Valve Diameter: 36.0 mm (1.42 in).
Valve Stem Diameter: 9.0 mm (0.35 in) for both intake and exhaust.
Valve Seat Inserts: Press-fit inserts; exhaust valve seats are manufactured from
heat-resistant alloy.
Valve Guides: Cast iron guides pressed into the cylinder head.
Valve Adjustment: Mechanical adjusters with threaded rocker arms and lock nuts.
Adjustment is performed with the engine cold.
Camshaft: Chilled cast iron camshaft with induction-hardened lobes. The camshaft
is supported by four bearings and driven by a duplex timing chain.
Combustion Chamber: Indirect injection configuration utilizing a pre-chamber
(swirl chamber) cast into the cylinder head. Fuel is injected into the
pre-chamber where partial combustion occurs before flame propagates into the
main combustion chamber. This design allows for smooth combustion and reduced
mechanical noise at the expense of cold-start performance.
Glow Plugs: Early variants utilized series-wired loop-type glow plugs. Late
variants and converted engines utilize parallel-wired pencil-type glow plugs for
improved cold-start reliability.
The fuel system employs a mechanical Bosch in-line
injection pump with indirect injection through pre-chambers. Injection Pump
Type: Bosch M-type (M- or MW-series) mechanical in-line pump with a mechanical
governor. The pump is driven by the timing chain from the crankshaft. Injection
Pump Configuration: Individual plunger and barrel assemblies for each cylinder,
with delivery valves controlling injection timing and duration.
Injectors: Mechanical pintle-type injectors with opening pressure of 115-125 bar
(1,668-1,813 psi). Injectors are connected to the injection pump by
high-pressure steel lines. Governor: Mechanical centrifugal governor integrated
into the injection pump, controlling idle speed and maximum engine speed without
electronic intervention. Fuel Lift Pump: Mechanical diaphragm pump mounted to
the cylinder head, operated by an eccentric lobe on the camshaft. The lift pump
draws fuel from the tank and supplies it to the injection pump.
Fuel Filter: Spin-on cartridge filter with an integrated water separator and
manual priming pump. Cold Start Device: Manual or automatic cold start advance
mechanism that adjusts injection timing to compensate for lower combustion
temperatures during engine warm-up. Engine Shutdown: Vacuum-operated shut-off
valve mounted on the injection pump. Vacuum is supplied by the engine-driven
vacuum pump and controlled by a solenoid valve activated by the ignition switch.
The lubrication system is a full-flow, pressurized
design utilizing a rotor-type oil pump driven by the crankshaft. Oil Pump Type:
Internal gear (gerotor) pump mounted to the front of the crankshaft, housed
within the timing cover assembly. Oil Capacity: 6.5 liters (6.9 qt) including
oil filter replacement. Recommended Oil Viscosity: 15W-40 or 20W-50 for standard
operating conditions; 10W-40 for colder climates. Oil Quality Requirement: API
CD, CE, CF, or later diesel-specific classifications.
Oil Pressure: At warm idle, pressure ranges from 0.8-1.5 bar (12-22 psi). At
3,000 rpm, pressure reaches 3.0-4.0 bar (44-58 psi). Oil Cooler: Not equipped as
standard. The large oil capacity provides sufficient thermal mass for the
engine’s heat load. Oil Filter: Full-flow spin-on canister type mounted to the
cylinder block. The filter incorporates a bypass valve to maintain oil flow if
the filter element becomes restricted.
Crankcase Ventilation: Open or closed system depending on market. Early variants
utilized a draft tube; later variants incorporated a closed system with a
breather hose routed to the air cleaner.
The cooling system is pressurized and utilizes a
centrifugal water pump driven by the accessory drive belt. Water Pump Type:
Centrifugal pump with a cast iron housing and stamped steel impeller.
Thermostat: Wax-pellet type located in the coolant outlet housing. Opening
temperature is 82-88 °C (180-190 °F). Coolant Capacity: 8.0-9.0 liters (8.5-9.5
qt) inclusive of engine block, heater core, and radiator.
Radiator: Cross-flow copper or aluminum core with plastic end tanks depending on
production year. Cooling fan configuration consists of an engine-driven
mechanical fan with a viscous clutch or a direct-drive fan on commercial
variants. System Pressure: Radiator cap rated at 1.0 bar (15 psi). Coolant
Specification: Ethylene glycol-based coolant with corrosion inhibitors suitable
for cast iron engine construction.
| Intake and Exhaust Systems |
Exhaust System: Cast iron exhaust manifold with a
single exhaust outlet. A single catalytic converter is not present on
pre-emissions variants; later export variants incorporate an oxidation catalyst.
Intake Manifold: Cast iron or aluminum manifold with individual runners per
cylinder. The intake manifold incorporates a pre-heating system using exhaust
gas recirculation (on later variants) or an electric heater element for
cold-weather operation.
Timing System: Duplex (double-row) roller timing chain
driven by the crankshaft. The chain drives the camshaft, injection pump, and
vacuum pump. A hydraulic or spring-loaded tensioner maintains chain tension. The
duplex chain design provides redundancy and extended service life compared to
single-row configurations.
Vacuum System: Engine-driven vane-type vacuum pump mounted to the cylinder head,
driven by the camshaft. The vacuum system supplies the brake booster, engine
shut-off valve, and (on automatic transmission variants) the transmission
modulator.
Starting System: 12-volt electric starter with a heavy-duty solenoid. Glow plug
pre-heating is required before cold starts; pre-heat duration ranges from 10-30
seconds depending on ambient temperature.
Overall Length: 720 mm (28.3 in) measured from
accessory drive pulley face to transmission mounting flange.
Overall Width: 580 mm (22.8 in) inclusive of injection pump and intake manifold.
Overall Height: 760 mm (29.9 in) from oil pan bottom surface to valve cover top
surface.
Dry Weight: 195-210 kg (430-463 lb) depending on accessory drive components and
sump configuration.
Valve Clearance (cold): Intake 0.10-0.15 mm
(0.004-0.006 in); Exhaust 0.25-0.35 mm (0.010-0.014 in). Adjustment interval is
24,000 km (15,000 miles). Timing Chain Inspection Interval: Chain and tensioner
inspection recommended at 120,000 km (75,000 miles). Duplex chain replacement
intervals extend beyond 200,000 km (124,000 miles) under normal service.
Injection Pump Timing: Static injection timing set to 24°-26° BTDC for early
variants; 20°-22° BTDC for late variants. Timing is adjusted by shim selection
on the injection pump mounting flange. Injector Opening Pressure: 115-125 bar
(1,668-1,813 psi). Inspection interval is 48,000 km (30,000 miles). Glow Plug
Replacement Interval: Replace as required; resistance testing recommended at
48,000 km (30,000 miles).
Drive Belt Tension (Accessory): 10-12 mm (0.39-0.47 in) deflection under 10 kg
(22 lb) of force at the midpoint of the longest span. Coolant Change Interval:
48,000 km (30,000 miles) or 2 years. Engine Oil Change Interval: 7,500-10,000 km
(4,700-6,200 miles) depending on operating conditions and oil quality. Idle
Speed (warm, neutral): 650-750 rpm. Fuel Filter Change Interval: 30,000 km
(18,600 miles) or as indicated by water-in-fuel sensor.
Cylinder Head Bolts (cold), Step 1: 40 Nm (30 lb-ft).
Cylinder Head Bolts (cold), Step 2: 80 Nm (59 lb-ft).
Cylinder Head Bolts (cold), Step 3: 130-140 Nm (96-103 lb-ft) for M12 bolts.
Crankshaft Damper Pulley Bolt: 200-220 Nm (148-162 lb-ft).
Connecting Rod Cap Nuts: 50-55 Nm (37-41 lb-ft).
Main Bearing Cap Bolts: 80-85 Nm (59-63 lb-ft).
Camshaft Bearing Cap Bolts: 20-25 Nm (15-18 lb-ft).
Camshaft Sprocket Bolt: 80-90 Nm (59-66 lb-ft).
Valve Cover Nuts: 8-10 Nm (6-7 lb-ft).
Rocker Arm Shaft Bolts: 20-25 Nm (15-18 lb-ft).
Intake Manifold Nuts: 20-25 Nm (15-18 lb-ft).
Exhaust Manifold Nuts: 30-35 Nm (22-26 lb-ft).
Oil Pan Bolts: 10-12 Nm (7-9 lb-ft).
Oil Pump Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Timing Chain Tensioner Bolt: 50-60 Nm (37-44 lb-ft).
Water Pump Bolts: 20-25 Nm (15-18 lb-ft).
Injection Pump Mounting Nuts: 20-25 Nm (15-18 lb-ft).
Injection Line Fittings: 20-25 Nm (15-18 lb-ft).
Injector Hold-Down Clamps: 30-35 Nm (22-26 lb-ft).
Flywheel / Drive Plate Bolts: 90-100 Nm (66-74 lb-ft).
Glow Plugs: 20-25 Nm (15-18 lb-ft).
Mercedes-Benz 240D (W115): 1973-1976. The OM616.912
powered the W115-series 240D, producing 64 hp (48 kW).
Mercedes-Benz 240D (W123): 1976-1985. The OM616.912 (early) and OM616.940 (late)
powered the W123 240D across its production life. Late variants produced 71 hp
(53 kW).
Mercedes-Benz 240 GD (W460 G-Class): 1979-1987. The OM616.931 was installed in
the G-Class short-wheelbase and long-wheelbase variants, featuring a reinforced
oil sump and revised engine mounts for off-road operation.
Mercedes-Benz T1 Transporter (307 D, 308 D, 407 D): 1977-1985. The OM616 powered
these light commercial vans and chassis-cab configurations, with power output
calibrated for commercial duty cycles.
Mercedes-Benz L 407 D / L 408 D (Light Truck): 1970s-1980s. The OM616 was
utilized in light-duty commercial trucks and delivery vehicles.
Unimog 421: Selected variants of the Unimog 421 series received the OM616 for
light-duty agricultural and municipal applications.
Force Motors Trax / Gurkha (India): Licensed production of the OM616 continued
under Force Motors (formerly Bajaj Tempo) into the 2010s. These variants
incorporated turbocharging, intercooling, and electronic injection upgrades,
producing approximately 90 hp (67 kW) and 186 Nm (137 lb-ft). Applications
included the Force Trax utility vehicle and the Force Gurkha off-road vehicle.
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