Is the M104 engine good?  

This blog will answer the following questions: is the M104 engine good? What are the technical specifications of the M104 engine? What are the different versions of the M104 Engines? Which models used the M104 engine? What are the common problems in the M104 engine?

Is the M104 engine good?  

Yes, the M104 is one of the good engines manufactured by Mercedes Benz. The production of the M104 engine started in 1989 and lasted for almost 10 years. Mercedes Benz used the M104 in vans and passenger cars. Because of its strong engine block, the M104 can also be turbocharged to increase engine output without any modifications to the mechanical components.

The Turbocharger installations were mostly performed in the W140 passenger cars by well-known tuners. 75 units of W140 with Turbocharged M104 engine were also sold by an authorized Mercedes Benz dealer in Beaconsfield.

The M104 used overhead camshafts with cross-flow valves, the design allowed for better extraction of the exhaust gasses. The inline 6 cylinders M104 design was also reverse engineered by Toyota to make its 1FZ-FE engine that was mostly used in passenger cars.

What are the technical specifications of the M104 engine?

The technical specifications of the M104 engine are given in the table below:

Mercedes Benz adapted the design for the M104 engine from the VR 6 engine of Volkswagen. V configuration is ideally more suitable for dynamic balancing but it takes too much space in the vehicle. Mercedes Benz wanted a compact engine for its Vito van. VR 6 engine has the same cylinder head for both the banks of the cylinders. 

The engine block is smaller than a straight six or a V six configuration. Hence the M104 engine can be used in over 40 different models in the Mercedes Benz product line-up. The M104 engine has double overhead camshafts that allow for variable valve timings which improve the torque characteristics.

The variable timing is only present on the intake camshaft. It is controlled by an electromagnetic clutch. When the engine speed increases, the camshaft can be switched to early timing which improves the cylinder loading. The late timing was for low engine speeds and during starting the engine. Unlike modern engines, there is no precise adjustment. The change in the timing can be felt when driving the car.

M104 also uses an electronic fuel management system designed by Bosh. The ignition and fuel injection is controlled by a single control unit. The electronic control unit is connected to an air-mass sensor to measure the quantity of air entering the intake manifold.

The moving parts of the engine are lubricated by the engine oil, an oil pump is mechanically driven by the crankshaft. The overall engine oil capacity is 7.5 liter, the oil filter is also replaced at the time of replacing the engine oil.

Overall the M104 offered great performance and fuel efficiency. The fuel consumption on highways is 8.5L/ 100 Km and in the city, it’s 14 L/ 100Km. The M104 engine is water cooled, there is a fan operated by a clutch. The clutch pulley is driven by the crankshaft via the poly V-belt.

What are the different versions of the M104 Engines?

The different versions of the M104 engine are given in the table below:

The M104.980 and M104.941 are high-performance engines tuned by AMG. The 3.4 version was the version of the M104 that was tuned when AMG was not a part of the Daimler Benz corporations. Hence it was basically a conversion of the standard 3.0 L M104 engine.

The power produced by the 3.4 L M104 is 270 horsepower. AMG also increased the maximum engine speed limit by using a modified crankshaft and Bosch KE- Jetronic fuel injection system.

The 3.6 L M104.941 was developed by the AMG from the ground up. It featured lightweight but durable pistons and connecting rods. The crankshaft was taken from the OM603 diesel engine which was used in the 350 sd.

The power output of the 3.6 L AMG M104 is more than 270 hp at 5000 RPM. The increase in displacement is achieved by increasing the stroke of the cylinder instead of increasing the bore. The over-square nature of the engine limited the maximum engine speed but it also allowed for more torque.

Which Mercedes Benz cars used the M104 engine?

The following cars used the M104 engine:

What are the common problems in the M104 engine?

The common problems in the M104 engine are given below, these problems occur in poorly maintained engines.

• Engine overheating

The M104 uses a mechanical clutch in the engine fan, it is driven by the belt drive of the engine. The clutch acts as an overrun pulley and protects the fan when the engine is overrun. However, this pulley malfunctions in vehicles with high mileage.

The fan does not work even after the engine is running, causing the coolant in the engine to overheat. The remedy is to replace the pulley but there can be damage to the cylinder head gasket if the vehicle is driven in an overheated condition.

• Rough idle or surges

This problem is very common in the M104, poor idling and surges in the engine speeds are because of a faulty air mass sensor. The electronics fuel injection control unit keeps attempting to adjust the air-fuel mixture. This creates poor idle characteristics as the measured air quantity is incorrect.

Replacing the air mass is the only remedy to fix this issue, if a fault occurs again then there can be unmetered air entering the 

Conclusion

This blog explained the technical specifications of the M104 engine and also listed some of its common problems. The M104 was later replaced by the M112 engine in 1996, however, Mercedes Benz continued to produce the M104 for a few more years due to its popularity.