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Common Issues of the Mercedes-Benz M278 Engine: A Comprehensive Guide

Updated: Feb 27

When it comes to luxury vehicles, the Mercedes-Benz brand has long been synonymous with innovation and performance. The M278 engine, featured in a range of models, has certainly contributed to this reputation. However, like any complex machinery, it is not immune to common issues that can arise over time. In this blog post, we will explore some of the prevalent concerns associated with the Mercedes-Benz M278 engine, helping owners and enthusiasts better understand and address these challenges.

1. Oil Leaks: Engine oil leaks are a common headache for M278 owners. Faulty gaskets and seals can lead to oil seepage, affecting engine performance and potentially causing damage. The two most common leaks you will encounter on the M278 are the Upper Front Timing Covers, the Oil Filter Housing, and the Camshaft Plugs. Routine inspections and addressing leaks promptly can help maintain the engine's health and longevity.

2. Coolant Leaks: Cooling system problems, such as coolant leaks, can jeopardize the engine's ability to regulate temperature. Faulty hoses, plastic turbo coolant lines, radiator issues, or a malfunctioning water pump are potential culprits. The Oil Filter Housing and oil cooler are another common culprit, having the potential of allowing your oil and coolant to mix together. Regular checks of the cooling system can prevent overheating and subsequent engine damage.

3. Camshaft Adjuster & Camshaft Failure: The M278 engine employs variable camshaft timing for improved performance and efficiency. However, the camshaft adjuster can fail over time, causing excessive rattle noise on startup, issues with the variable valve timing system, and in serious cases, may even cause damage to the camshaft causing an extended crank on startup, or even a no-start. This issue can set off the codes P001685, P001785, P001177, and/or P001885. Replacement of the camshaft adjuster, and potentially the camshaft, is essential to maintain optimal engine performance and correct the issue.

4. Timing Chain Tensioner Issues: One of the most reported problems with the M278 engine is related to the timing chain tensioner. Over time, these tensioners may wear out, leading to timing chain slack and potential engine damage. This issue is primarily caused by the engine not having a check valve which ensures the tensioner has the proper oil pressure when starting. This leads to premature wear of the tensioner.

5. Ignition Coils: Ignition coils are critical components in the M278 engine's ignition system. Over time, these coils may fail, leading to misfires, rough idling, and decreased performance. Regular inspection and prompt replacement of faulty ignition coils can help maintain the engine's smooth operation. We recommend checking and replacing the Ignition Coils between 60K-80K miles.

6. Fuel Injector Failures: Fuel injectors are vital components that ensure precise fuel delivery to the engine. Failures in the M278's fuel injectors can lead to rough idling, decreased fuel efficiency, and poor overall performance. Regular fuel system maintenance and using high-quality fuel can help mitigate these issues.

7. Turbocharger Problems: Turbochargers play a crucial role in enhancing the M278 engine's performance. However, issues such as oil leaks, worn bearings, or malfunctioning wastegates can occur. Regularly checking for unusual noises, reduced power, or changes in exhaust smoke color can help detect turbocharger problems early on.

8. Carbon Buildup: Carbon buildup on intake valves and in the combustion chamber is a common problem in direct injection engines, including the M278. This buildup can affect engine efficiency and performance. Regular use of quality fuel additives and periodic carbon cleaning can help combat this issue.


While the Mercedes-Benz M278 engine is a remarkable piece of engineering, it is essential for owners to be aware of common issues and proactive in their maintenance approach. Regular inspections, timely repairs, and adherence to manufacturer-recommended maintenance schedules can go a long way in ensuring the longevity and optimal performance of this sophisticated engine. By staying informed and addressing issues promptly, Mercedes-Benz enthusiasts can continue to enjoy the driving experience that the M278 engine was designed to deliver.

Need Mercedes-Benz Service or Repair?

If you have stumbled upon this blog post seeking advice on how to properly care for your Mercedes-Benz, or you have a specific concern and have come to Google to see how serious it is, get in touch with us! 603 MTech Autowerks is New England's most innovative European auto repair shop specializing in Mercedes-Benz service and repair.

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