In 2008, the four-cylinder OM 651 diesel was praised by its creators as a "miracle engine" that even made it into the S-Class in 2010. With the four-cylinder, Mercedes Development Board member Thomas Weber wanted to prove that the large luxury sedan from Mercedes-Benz can also be operated spiritedly and economically. In terms of the theoretical values, this corresponded to reality. With 204 hp, a maximum torque of 500 Newton meters and a consumption of around five liters, even the S-Class format can be moved properly.
Just one year after its market launch, the Frankfurter Allgemeine headlined: "A miracle engine that turned into a disaster". That sounded exaggerated, but given the recall costs of around 500 million euros, it was quite a disaster for the Daimler balance sheet. The piezoelectronically controlled injection nozzles from the American supplier Delphi were to blame. The engine switched to emergency mode in the event of incorrect injections. CEO called the problem "a teething problem" of the new engine, but which you have under control. Given the 300.000 vehicles to be repaired, that sounded rather unrealistic. Daimler recovered part of the Delphi costs, reassured affected customers with interesting incentives, but the trouble remained. Technically, Mercedes switched from piezo injectors to magnetically controlled injection.
Now the engine, which is installed to varying degrees in almost all series, is causing trouble again. This time it is leaking engine oil on a defective sealing ring of the chain tensioner. The technicians have determined that this could lead to the chain coming off. "With this engine, the worm is simply in there," scolds a Mercedes developer. In the past few years there have been minor defects, which, however, would not have required a recall. The exchange of the sealing ring should be expensive, because a working time of up to 90 minutes is expected. According to Daimler, the affected vehicles were produced between February and November 2014. In contrast, the Federal Motor Transport Authority states that the production period from 2008 to 2014 is affected - which actually affects the entire production period.
"We expected too much from this engine," says one developer. “We wanted to bring a new engine that is more economical than all others and that can be built cost-effectively. That was just too much of a requirement. "