"If you're not getting the 265HP version of the OM642, I would instead just go for the OM651 E250 Bluetec — mbworld.org forum member"
RISKY
58/ 100
"Capable diesel hiding expensive gremlins"
261
Max HP
620
Torque Nm
10,000
Oil interval km
0
Recalls
5
Known issues
Known Issues
Timing Chain Wear and Tensioner Failure€1,500-3,500 · 120,000-200,000 kmCRITICAL
The OM642 timing chain and tensioner are known to wear prematurely, particularly when oil changes are neglected or extended. Forum members report that visible notches on the chain tensioner indicate a stretched chain requiring immediate replacement. All reported cases of excessive chain wear are linked to maintenance lapses.
Rattling noise on cold start from front of engine
Four notches visible on chain tensioner
Engine warning lights
Rough idle or misfires
DIY: Expert — requires engine removal or significant disassembly
EGR Valve and EGR Cooler Failure€400-1,200 · 100,000-180,000 kmHIGH
EGR faults are a well-documented recurring issue on the OM642. Symptoms include limp mode activation, fault codes at operating temperature, and rough running. EGR cooler leaks and clogged EGR valves are frequently reported across multiple forums. Many owners opt for EGR delete or blanking as a long-term solution.
Engine enters limp mode
EGR-related fault codes
Rough idle and poor throttle response
Excessive exhaust smell at idle
DIY: Moderate — accessible with basic tools but requires EGR system knowledge
Swirl Flap Motor and Intake Manifold Failure€300-900 · 100,000-160,000 kmHIGH
The intake manifold swirl flap actuator motor is a known failure point on the OM642. Overloaded or seized flap motors cause drivability issues. Many owners and tuners recommend swirl flap delete as a preventative measure. The resistor hack is a temporary workaround but full deletion or motor replacement is advised.
Rough idle and hesitation
Intake manifold-related fault codes
Reduced power under load
Check engine light
DIY: Moderate — intake manifold removal required
Turbocharger and Actuator Wear€800-2,500 · 150,000-250,000 kmHIGH
Forum sources note that OM642 turbos and actuators are considered more fragile than those on the older OM648. Turbo actuator failures are reported, particularly on higher-mileage units. Regular oil changes and warm-up/cool-down cycles are critical to turbo longevity.
Loss of power or boost
Excessive smoke under acceleration
Turbo whine or grinding noise
Limp mode activation
DIY: Hard — turbo access is restricted on V6 layout
Intercooler Pipe and Boost Hose Oil Leaks€100-400 · 80,000-150,000 kmMODERATE
Small oil leaks from intercooler pipes, O-rings, and breather connections are commonly reported by OM642 owners. These are typically not catastrophic but can lead to reduced boost and dirty intake components if left unattended.
Oily residue around intercooler pipes
Slight reduction in performance
Boost hose blowoff under hard acceleration
DIY: Low — accessible with basic tools
Advertisement
Buying Checklist
Pull a full OBD scan for EGR, swirl flap, and turbo actuator fault codes before purchase
Check timing chain tensioner notch count and ask for documented evidence of chain replacement if over 150,000 km
Verify full service history with oil changes at no more than 10,000 km intervals using approved MB specification oil
Inspect all intercooler pipes and charge hose O-rings for oil residue or cracking
Test drive at full operating temperature and confirm no limp mode activation under hard acceleration
Check for coolant loss or sweet smell from exhaust that could indicate EGR cooler leakage
Service Reality
Community oil interval10,000 km
Oil specificationMB 229.51 or 229.52 0W-30 or 5W-30 fully synthetic
Est. ownership cost (2yr)€1,500-4,500 over first two years depending on deferred maintenance
The OM642 is a smooth and torquey diesel that rewards careful ownership but punishes neglect with expensive bills. Prioritise examples with documented service history and avoid any car with unknown oil change intervals, as timing chain issues are directly linked to maintenance lapses. Budget for preemptive swirl flap deletion and EGR servicing regardless of reported condition, as these are near-universal costs on high-mileage units. A pre-purchase inspection by a Mercedes specialist is strongly recommended before committing.
Parts People Buy
OM642 Timing Chain Kit with Tensioner and Guide RailsLink unavailable