Teardown Shows Why This Mercedes Diesel Engine Failed

Not Your Typical Four-CylinderWhile Mercedes-Benz, like most automakers, is now shifting toward downsized, electrified powertrains, the German marque introduced the 2.1-liter turbodiesel OM651 diesel engine almost two decades ago – an engine often described as “overbuilt.” The diesel engine has received mixed reviews when it comes to reliability, with some critics pointing to issues such as timing chain wear and oil leaks, particularly in higher-mileage examples.The OM651 had a relatively limited presence in the U.S., but thanks to Eric from I Do Cars, this failed example was torn down to show the kinds of issues it could develop. Based on the date codes and part numbers, it was believed to have come from a 2015 GLK 250 BlueTEC 4MATIC, which produced around 200 horsepower and 369 lb-ft of torque. The engine weighs roughly 400 pounds, which is relatively heavy for a four-cylinder and made the teardown a bit more c …