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
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.
Verdict and scores are editorial opinions based on aggregated data. Learn about our methodology. Not a substitute for professional inspection.