Autoscore logo

Mercedes-Benz OM642

OM642 Engine

The OM642 is a diesel engine manufactured by Mercedes-Benz. It has a displacement of 3.0 liters and was produced from 2005 to 2018.

Typical Use Cases

  • Mercedes E-Class (W211/W212): 2005–2016
  • Mercedes S-Class (W221): 2006–2013
  • Mercedes GL/GLE (X164/W166): 2006–2018
  • Mercedes ML (W164/W166): 2005–2015
  • Mercedes R-Class (W251): 2006–2017

This overview summarizes the reliability of the Mercedes-Benz OM642, including common issues and cost drivers.

Mercedes-Benz OM642 engine
Image credit: Wikimedia Commons · CC BY-SA

Technical Specifications

Manufacturer
Mercedes-Benz
Fuel Type
Diesel
Displacement
3.0 L
Production
2005–2018
Power Output
190 hp
Emissions
Euro 4, Euro 5, Euro 6

Reliability Analysis

Overall Reliability Summary

The engine's reliability can be assessed as moderate, with some notable concerns stemming from identified risks and issues. The risk score of 6.0 (on a scale where lower values indicate minimal risk and higher values signal greater potential for problems) translates practically to a system that operates reliably in routine conditions but may encounter disruptions in demanding or edge-case scenarios, such as high-load operations or extended use. This score reflects a balanced but imperfect stability profile, where preventive maintenance or monitoring could mitigate foreseeable challenges.

Contributing to this assessment are two known issues: one classified as critical, which could result in substantial operational failures or safety implications if triggered, and one medium-severity issue, likely causing intermittent performance degradation without immediate catastrophe. Overall, these factors suggest the engine is functional for standard applications but warrants careful evaluation of its deployment context to avoid amplified risks from the critical issue.

Conditionally Recommended

Autoscore Verdict

Conditionally recommended. Risk score of 6.0 indicates moderate risks that can be managed with proper implementation and monitoring.

Risk Score
6
out of 10

Common Problems & Weak Points

IssueTypical MileageRepair Cost (Est.)Severity
Swirl Flap Failure~150,000 km5000 – €8000High
Injector Leakage~200,000 km1500 – €2500Medium

Swirl Flap Failure

This is a known issue called swirl flap failure in the engine's intake manifold. The swirl flaps can break off and get pulled into the cylinders, which leads to severe engine damage that often requires a full engine replacement.

It typically occurs around 150,000 km, with a medium probability of happening. The severity is critical, and repairs usually cost between 5,000 and 8,000 euros. If you're considering this car, it's worth checking the service history for any related work or inspections.

Typical Mileage: 150,000 km
Cost: 50008000

Injector Leakage

This car model has a known issue with injector leakage, where the seals around the fuel injectors can leak over time. This leads to black smoke from the exhaust and difficulty starting the engine. It's common in high-mileage vehicles, typically showing up around 200,000 km. The probability of it occurring is high, and it's considered a medium-severity problem. If it needs repair, expect costs between 1,500 and 2,500 euros.

Typical Mileage: 200,000 km
Cost: 15002500

Buyer's Inspection Checklist

  • Inspect the intake manifold and cylinders for signs of damage or debris from broken swirl flaps, which can cause severe engine failure.
  • Check the fuel injectors and seals for leaks, particularly on high-mileage engines, to avoid black smoke and hard starting issues.

Frequently Asked Questions

Is the OM642 engine reliable?

The OM642 has known weak points, but with good maintenance the reliability is solid. See the risk analysis and common problems for specifics. Start a report for a specific car.

How expensive are typical repairs?

Common repairs fall into a mid-range cost band depending on the issue and workshop. Check the cost ranges in the table. Use the used car report for specific listings.

Which model years are best for this engine?

Newer production years often include technical updates. Review the production years and revisions in the specs. Use Car Check for quick screening.

Related Engines