Is the Mercedes Benz 2.7 litre engine reliable?

In this article, we find out if the Mercedes Benz 2.7 litre diesel engine is reliable? Which models used the 2.7 litre Mercedes Benz diesel engine? What are the common problems in the 2.7 litre Mercedes Benz diesel engine?

Is the Mercedes Benz 2.7 litre engine reliable?

Yes, the  Mercedes Benz 2.7 litre diesel is a reliable engine. The 2.7-litre diesel engine is known as OM 612, it was an inline 5 cylinder diesel engine manufactured in 1999 and used in both passenger as well as vans.

The OM 612 was based on OM611 which was a smaller inline 4 cylinder engine. OM612 has two versions, one was the 2.7 litre that produced 160 horsepower and 370 NM of torque. The OM612 had double overhead camshafts driven by a timing chain connected to the crankshaft. 

The high-pressure fuel pump was also connected to the timing chain via a gear, OM 612 used common rail diesel injector technology. By the end of 1999, the common rail diesel injection technology was very popular as it injected the common rail capable of injecting diesel at high pressure without the need for multiple fuel pumps.

Mercedes Benz started using Common rail diesel injection in 1997. It was first used in the OM611 engine which was a 2.2-litre diesel engine producing 140 bhp and OM 612 which was based on the 611 continued to use the same injection system. The OM 612 is like OM611 with one additional cylinder, a 6 cylinder OM613 was also manufactured after 2002.

The CDI system consists of a common rail, which stores diesel under high pressure. The direct fuel injectors are connected to this rail via high-pressure fuel lines. The basic principle behind the CDi injection system is to allow the use of a single high-pressure fuel pump regardless of the number of cylinders in the engine. 

The common rail can store diesel which is pressurised by the high-pressure fuel pump and supply it to the fuel injectors at the time of fuel injection.  Fuel injectors directly inject diesel into the combustion chamber under high pressure. Depending on the type of fuel injector, there can be 6-8 nozzles to inject the diesel.

The fuel injectors are calibrated at the time of production and the data is stored in the form of an IMA code. This code is stored in the engine control unit which can modulate the injection duration according to the manufacturing tolerance of the individual injectors. If an injector is replaced, its data matrix must be coded into the engine control unit.

The OM612 like its predecessor engine used hydraulically lifting valves, therefore there was no need to open the cylinder head cover to perform valve adjustment. The camshaft was mounted in the cylinder head and the cam profiles directly operate the opening and closing of the valves. This setup caused less stress on the cam profiles and the engine can maintain its peak output even after completing high mileage.

Which models used the 2.7 litre Mercedes Benz diesel engine?

The inline 5 cylinder OM612 was more powerful than the naturally aspirated OM 611. It was also turbocharged with an air-cooled intercooler, the 2.7-litre displacement effortlessly produced more than 160 horsepower.

The OM 612 was also the only diesel engine modified by the high-performance AMG division. The modified OM612 was a 3.0-litre engine and produced 230 horsepower and 540 Nm of torque. Following are the models that used the OM612.

  • E class W210
  • C class W203
  • C 30 AMG
  • Sprinter 
  • G wagon W463

Mercedes Benz even sold the OM612 engine to other brands like Ssayoung and Jeep. the company used the OM 612 in the following models

What are the common problems in the 2.7 litres OM 612 Mercedes Benz diesel engine?

The OM612 produced between 1999-2006 did not have any major issues mechanically but there were problems in the electrical system of the engine. Following are some of the common problems:

  • Crankshaft position sensor

The crankshaft position sensor is a hall effect sensor that determines the position of the crankshaft.  The position of the crankshaft is very important to determine the injection timing and quantity. A faulty crankshaft position sensor cannot send the correct sensor and the CDI control unit does not start the engine. 

The engine keeps on turning until the battery is dead. The only solution is to replace the faulty CKP sensor. Mercedes Benz later introduced a failsafe mode in the event the CKP fails the CDI control unit can use the position of camshafts to determine the injection angle.

  • Engine wiring harness

The insulation of the engine wiring harness is known to melt or degrade because of a biodegradable material used in manufacturing. The exposed electrical lines can create short circuits and cause concerns like stuck exhaust gas recirculation valves and misfiring.

Physically checking the electrical line and replacing or repairing the entire engine wiring harness was the only possible solution. 

Other articles about Mercedes Benz you may be interested in

Is Mercedes Benz considered a  luxury brand?

Does Mercedes Benz use a biodegradable electrical wiring harness?

Is the 2005 Mercedes Benz E55 AMG a good car?  


The 2.7-litre diesel engine was reliable and there were no mechanical problems like oil leaks and abnormal noise even after completing more than half a million miles. Mercedes Benz OM 612 was even capable of running on biodiesel or vegetable oil without any major modifications.

FAQs: is the Mercedes Benz 2.7 litre diesel engine reliable?

Which is the most reliable Mercedes diesel engine?

Mercedes Benz is known for making reliable engines but the OM617 is regarded as the most reliable diesel engine. Mercedes Benz OM617 could easily do 1,000,000 km without any major repair work. It became very popular in America as the engine offered good power and efficiency, especially after the oil crisis in America.

How reliable are Mercedes diesel engines?

Mercedes Benz diesel engines are very reliable. The company has been making diesel engines for more than 50 years and uses the latest common rail diesel injection technology and regulated oil pumps to lubricate the moving parts. 

Are Mercedes Bluetec engines reliable?

Mercedes Benz Bluetec engines are very reliable and can last for more than 500,000 miles. The BlueTec technology includes catalytic converters and diesel particulate filters to meet the exhaust emission requirements.

Which Mercedes engine is the best petrol or diesel?

Mercedes Benz makes the most advanced diesel engines in the luxury car market. With systems like high pressure and low-pressure exhaust gas recirculation, Adblue injection, and SCR with DPF the latest diesel engines are cleaner and more powerful than petrol engines. Therefore, Mercedes Benz diesel engines are the best engines.