OM642
Mercedes-Benz · 3.0L V6 Diesel
2005–2020
"Legendary V6 diesel. 250k+ km. Fix swirl flaps and enjoy."
Mileage Risk Timeline
When problems typically appear — enter your mileage to see your risk zone
Known Issues 3
Valley oil cooler seal failure — #1 issue
▸Coolant in oil (milky oil on dipstick), oil in coolant (brown sludge in expansion tank), overheating
Oil cooler sits in engine valley. Seals fail allowing coolant/oil mixing. Key reason score dropped from BEST to CAUTION. Fix proactively — ignoring causes engine damage.
Very important pre-purchase check on any OM642. Check oil dipstick (milky = coolant mixing). Budget €800-2000 for repair. Greek diesel specialists familiar.
Intake swirl flap actuator failure
▸Rough idle, check engine light, intake rattle
Early OM642 (pre-2010) has plastic swirl flap actuators that break. Fragments can enter engine. Permanent fix: remove and block off.
Check production year. Pre-2010 OM642: verify swirl flaps removed or intact. Simple preventive fix.
BlueTEC NOx system / DEF issues (where fitted)
▸NOx warning light, SCR system faults, AdBlue consumption
BlueTEC models have NOx after-treatment. Part of $700M MB settlement in USA. System can fault.
Verify if car has BlueTEC system and if recall/settlement updates applied. DEF fluid widely available in Greece.
Models with OM642 13
Related Guides
Other Mercedes-Benz Engines
Tuning Potential
Moderate — 280hp
Frequently Asked Questions
Is the Mercedes-Benz OM642 reliable?
The Mercedes-Benz OM642 scores 82/100 with a verdict of BUY. It has 3 documented issues with total repair costs between €1,500 and €4,400.
What are the common problems with the OM642?
The most common issues are:
- Valley oil cooler seal failure — #1 issue — high, repair cost €800–€2,000, 80,000 km–150,000 km
- Intake swirl flap actuator failure — moderate, repair cost €400–€900, 60,000 km–130,000 km
- BlueTEC NOx system / DEF issues (where fitted) — moderate, repair cost €300–€1,500, 60,000 km–∞
What cars use the Mercedes-Benz OM642?
How much does it cost to repair the OM642?
Total potential repair costs for all 3 known issues range from €1,500 to €4,400. The most expensive issue is typically .
What years was the OM642 produced?
The Mercedes-Benz OM642 was produced from 2005 to 2020. It is a 2987cc V6 diesel engine.
Scores are calculated from documented issues, repair costs, and failure patterns across thousands of owner reports and technical sources. Learn about our methodology. Always inspect before you buy.