| Home / Car Engines / Mercedes-Benz Engines / Mercedes-Benz M104 |
Mercedes-Benz M104 Specifications
| Engine Model: Mercedes-Benz M104 |
| Engine Type: 4-cycle inline 6-cylinder DOHC 12-valve liquid-cooled gasoline |
| Total Displacement: 171 cu.in (2.8 L), 195 cu.in (3.2 L), 219 cu.in (3.6 L) |
| Rated Engine Power: 193-272 Hp (144-203 kW) at 6000 rpm |
| Fuel System Type: Mechanical or electronic fuel injection |
____________________________________________________________________________________
- Mercedes-Benz M113K Engine Specifications
- Mercedes-Benz M159 Engine Specifications
- Mercedes-Benz M186 Engine Specifications
| General Technical Data |
The Mercedes-Benz M104 engine is an inline-six
cylinder, dual overhead camshaft powerplant introduced in 1989. It
succeeded the M103 engine, with a primary advancement being the
implementation of four valves per cylinder. Renowned for its robust
construction, smooth operation, and significant torque output, the M104
established a reputation for durability and engineering excellence.
It was produced in displacements of 2.8 liters, 3.2 liters, and a
flagship 3.6 liters. The engine family features a cast iron cylinder
block with a lightweight aluminum alloy cylinder head. A hallmark of the
M104 is its mechanical/electronic Bosch KE-Jetronic or, in later
versions, HFM engine management system. This engine served as a
cornerstone for Mercedes-Benz models throughout the 1990s, providing a
blend of refined performance and steadfast reliability.
Engine family: Mercedes-Benz M104
Engine type: Inline-six cylinder, four-stroke Otto cycle
Displacements: 2.8 liters (2799 cc), 3.2 liters (3199 cc), 3.6 liters
(3605 cc).
Bore: 89.9 mm (3.539 inches) for 2.8L and 3.2L; 91.0 mm (3.583 inches)
for 3.6L.
Stroke: 73.5 mm (2.894 inches) for 2.8L; 84.0 mm (3.307 inches) for 3.2L
and 3.6L.
Compression ratio: 10.0:1 for most applications; 9.2:1 for certain
markets with lower octane fuel.
Maximum power output: Ranges from 193 Hp (144 kW) for early 2.8L to 272
Hp (203 kW) for the 3.6L AMG variant.
Maximum torque output: Ranges from 199 lb-ft (270 Nm) for early 2.8L to
284 lb-ft (385 Nm) for the 3.6L. Firing order: 1-5-3-6-2-4.
Engine orientation: Longitudinal.
Aspiration: Naturally aspirated.
Fuel type: Premium unleaded gasoline (91 RON minimum).
Recommended oil grade: SAE 10W-40 or 15W-40, meeting Mercedes-Benz
specification 229.1.
Oil capacity: 7.0 liters (7.4 U.S. quarts), including filter.
Coolant capacity: 10.5 liters (11.1 U.S. quarts).
| Cylinder Block |
The cylinder block is manufactured from grey cast iron, providing high strength and excellent acoustic damping properties. It is a closed-deck design, enhancing rigidity and allowing for high cylinder pressures. The block incorporates six cylinders, cast integrally. The crankshaft is supported by four main bearing caps, also made of cast iron and secured with vertical bolts and two additional cross-bolts per cap, creating a rigid lower end structure.
Cylinder bore spacing is 99 mm (3.898 inches). The crankshaft is a forged steel component with seven main journals and six crankpins. It is internally counterweighted. Connecting rods are forged from steel, utilizing fracture-split cap technology for precise bearing alignment. Pistons are aluminum alloy, with a recessed crown to achieve the target compression ratio. Two compression rings and one oil control ring are fitted per piston.
| Cylinder Head and Valves |
The cylinder head is a single-piece casting from aluminum-silicon alloy (AlSi7Mg). It employs a dual overhead camshaft (DOHC) layout, with each camshaft operating twelve valves (two intake and two exhaust per cylinder). Valve actuation is via bucket-type hydraulic lifters, ensuring zero valve clearance maintenance. The camshafts are chain-driven from the crankshaft via a single-stage duplex roller chain.
The chain tension is controlled by a hydraulic tensioner. Intake valves have a head diameter of 30.5 mm (1.201 inches). Exhaust valves have a head diameter of 27.0 mm (1.063 inches). Valve stems are 6.0 mm (0.236 inches) in diameter. Valve seats are made from hardened material, and valve guides are pressed into the head. The intake ports are of a cross-flow design to improve volumetric efficiency.
| Fuel System |
Early production Mercedes-Benz M104 engines use the Bosch KE-Jetronic (K-Jetronic with electronic control) mechanical-electronic fuel injection system. This system employs a continuous fuel injection principle, with fuel quantity regulated by an airflow sensor plate and a differential pressure regulator, with electronic correction from an Engine Control Unit (ECU).
Later M104 engines, designated M104.94x, utilize the Bosch HFM (Hot Film Mass Airflow) engine management system. This is a fully electronic sequential fuel injection system. It uses a hot-film air mass meter for precise load calculation, a dedicated ECU, and electromagnetic fuel injectors. A fuel pressure regulator maintains constant pressure at the fuel rail. The electric fuel pump is located in the fuel tank. Fuel filter replacement is a scheduled maintenance item.
| Lubrication System |
The lubrication system is a pressure-fed, full-flow filtration wet-sump design. An oil pump is driven directly from the crankshaft via a short chain. The oil pump is a gear-type unit, located in the front engine cover. Oil is drawn from the sump through a pickup tube and screen, pressurized, and then forced through a full-flow oil filter.
From the filter, oil is directed into the main gallery of the cylinder block. It supplies the crankshaft main bearings and connecting rod bearings via drilled passages. A separate gallery feeds the cylinder head, lubricating the camshaft bearings, hydraulic lifters, and the chain tensioner. Oil pressure is monitored by a switch and a gauge sender unit. The oil pan is constructed from pressed steel.
| Cooling System |
The cooling system is a pressurized, forced-circulation type with a centrifugal water pump. The water pump is driven by the serpentine accessory drive belt. The thermostat is of a wax-pellet design, located in the housing on the cylinder head. The system uses a crossflow aluminum radiator with a plastic header tank. An electric cooling fan is thermostatically controlled, supplemented by a viscous clutch fan on some models.
| Other Systems |
The ignition system is a distributorless, static high-voltage distribution system. One ignition coil serves two cylinders (waste-spark system). Ignition timing is fully controlled by the ECU. The engine is equipped with a crankcase ventilation system that is closed and regulated by an oil separator. Exhaust gas recirculation is not used on this engine family.
| Dimensions and Weight |
The external dimensions of the M104 engine are constrained by its inline-six configuration. Approximate length is 700 mm (27.56 inches). Approximate width is 650 mm (25.59 inches). Approximate height is 700 mm (27.56 inches). These dimensions can vary slightly depending on attached accessories and manifold configurations. The dry weight of a complete M104 engine, including all fluids and standard accessories, is approximately 185 kg (408 lbs).
| Maintenance Data |
Engine oil and filter change interval is 10,000 miles (16,000 km) or 1 year under normal operating conditions. Severe service intervals are shorter. Spark plug replacement interval is 30,000 miles (48,000 km). The accessory drive belt (serpentine belt) should be inspected every 20,000 miles (32,000 km) and replaced if signs of wear or cracking are present.
The timing chain and its components are designed for the service life of the engine and do not have a scheduled replacement interval, but inspection is advised during major service. Valve clearance adjustment is automatic via hydraulic lifters, requiring no scheduled adjustment. Coolant replacement is recommended every 4 years or 80,000 km (50,000 miles). Air filter replacement interval is 20,000 miles (32,000 km).
| Tightening Torques |
All torque values are for clean, oil-free threads unless specified. Cylinder head bolts are tightened in a specific multi-stage sequence using the torque-plus-angle method: first pass 40 Nm (30 lb-ft), second pass 60 Nm (44 lb-ft), final pass tighten an additional 90 degrees. Main bearing cap bolts: 60 Nm (44 lb-ft) plus an additional 90 degrees.
Connecting rod cap bolts: 45 Nm (33 lb-ft) plus an additional 90 degrees. Crankshaft pulley bolt: 300 Nm (221 lb-ft). Camshaft sprocket bolts: 70 Nm (52 lb-ft). Spark plugs: 25 Nm (18 lb-ft). Oil drain plug: 40 Nm (30 lb-ft). Oil filter housing cap: 25 Nm (18 lb-ft).
| Vehicle Applications |
The Mercedes-Benz M104 engine was installed in a wide range of passenger vehicles from 1989 through 1999. Primary applications include: W124 chassis (E-Class: 300 E 2.8, 300 E 3.2, E 280, E 320). C124 chassis (E-Class Coupe). S124 chassis (E-Class Wagon). W140 chassis (S-Class: S 280, S 320, early S 350). C140 chassis (S-Class Coupe). R129 chassis (SL-Class: SL 280, SL 320, SL 300-24, SL 320).
W202 chassis (C-Class: C 280, C 36 AMG). The high-performance 3.6-liter variant, developed by AMG, was fitted to the 1993-1997 W124 300 CE 3.6 AMG, the 1992-1993 R129 SL 3.6 AMG, and the 1993-1997 W202 C 36 AMG. Production of the M104 ceased with the widespread adoption of the newer M112 V6 engine family.
____________________________________________________________________________________
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Industrial Engines Technical Specifications |
| Outboard Engines Technical Specifications |