Car Model Guide/ Mercedes-Benz/ C-Class/ S204/ C 320 CDI

C 320 CDI OM642

The V6 diesel. Effortless and long-lived, with two known age items: the oil cooler seals beneath the intake, and the swirl-flap linkage.

Overview

The C 320 CDI is the OM642 diesel version of the Mercedes-Benz C-Class wagon (S204), sold 2008–2011 with 224 PS and auto_7g. Demands diligence at level 3. A long-lived engine with two predictable age bills. The oil cooler seals under the intake and the swirl-flap linkage. 14 failure modes are recorded against its engine, gearbox, chassis and shared components. Prices on this page are illustrative placeholders rather than a sourced market sample. See the methodology for how the bands are derived.

Power224 PS

Torque510 Nm

Years2008–2011

Fueldiesel

DriveRWD

EnginesOM642

Biggest risks

Ranked by probability × repair cost. 14 recorded in total.

52Demands diligence

Oil cooler seal leak€900–€1,600checkable
DPF clogging and forced regeneration€250–€1,800partly checkable
Front control arm bushing wear€300–€700checkable

Risk level −22 · Likely spend vs price −26 · all issues →

System by system9 systems reviewed · 1 with no recurring fault reported

Engine⚠ attentionOil cooler seal leak, €900–€1,600.

Fuel system✓ clearNo recurring fault reported for this system on this engine.

Intake & airwatchIntake-port shut-off (swirl) actuator failure, €400–€900.

CoolingwatchCoolant expansion tank cracking, €120–€250.

Emissions⚠ attentionDPF clogging and forced regeneration, €250–€1,800.+1 more in this system

Transmissionwatch7G-Tronic conductor plate and 13-pin connector leak (722.9), €400–€900.+1 more in this system

ElectricswatchFootwell module (FRM) failure, €150–€700.+2 more in this system

Suspension & brakeswatchFront control arm bushing wear, €300–€700.+2 more in this system

Body & interiorwatchCorrosion at the rear subframe and arch seams, €300–€2,000.

Pre-facelift or facelift, this engine spans both

The same badge either side of the changeover. Bands are split at the facelift year from the generation record.

Phase	Years	Low	Average	High	Good buy	What differs
pre Pre-facelift	2008–2010	€5,050	€8,800	€14,700	€6,950	The specification the car launched with.
LCI Facelift (LCI)	2011	€5,500	€9,600	€16,000	€7,550	New front end and lights; revised interior; OM651 replaced OM646; M271 EVO replaced the supercharged M271

Known issues, ranked by expected cost

Faults recorded against this engine, its components and its chassis, ranked by likelihood × repair cost. Costs are indicative ranges with a stated labour basis.

Oil cooler seal leakOM642 3.0 V6 CDI€900–€1,600

Oil weeping down the back of the block, burning smell, oil in the valley beneath the intake. The oil cooler sits in the vee under the intake manifold and its seals harden with age. Access requires the intake off, so labour dominates the bill.

Check: Look down the back of the engine with a torch for wet oil and fresh cleaning. A suspiciously spotless engine bay on a 200,000 km V6 deserves a question.

EnginecommonDetectable at viewingevidence: documented150–280k km

DPF clogging and forced regenerationDPF€250–€1,800

Warning light, limp mode, oil level rising above the maximum mark from fuel dilution. The filter needs sustained hot running to regenerate. A car used for short urban trips never completes a regeneration cycle.

Check: Read the DPF soot load and the distance since the last regeneration on a scan tool, and check the engine oil level and smell it for diesel. Ask what the car was used for. A short-trip city diesel is the wrong car regardless of mileage.

EmissionscommonPartly detectableevidence: documented120–250k km

Front control arm bushing wearE9x chassis€300–€700

Knocking over bad surfaces, vague or wandering steering, uneven front tyre wear, steering shimmy under braking. The front lower arm bushings are a known wear item on this chassis and go well before the ball joints.

Check: Drive over a rough road at low speed with the windows down and listen. Check the inside edges of the front tyres for feathering.

SuspensionuniversalDetectable at viewingevidence: documented80–150k km

7G-Tronic conductor plate and 13-pin connector leak (722.9)7G-TRONIC€400–€900

Harsh, delayed or jerky shifts, holding a gear then banging the next in, and limp mode, often with speed-sensor or gear-ratio fault codes. The speed sensors in the conductor plate (mechatronic) fail, and/or the external 13-pin connector leaks fluid that wicks up the wiring into the control unit. Early units are the most affected.

Check: Test-drive through every gear cold and warm. Scan the transmission, and pull the external 13-pin plug to check for fluid on the pins.

TransmissioncommonPartly detectableevidence: documented120–220k km

Run-flat tyres and kerbed or cracked wheelsE9x chassis€150–€900

Harsh ride, vibration at speed, slow punctures. Stiff-sidewall run-flats transmit impacts straight into the rim, and these alloys crack rather than bend.

Check: Inspect the inner rim edge of every wheel for cracks and hairline splits, not just the face for kerbing. Budget for a set of conventional tyres; most owners switch and the ride improves markedly.

SuspensioncommonDetectable at viewingevidence: documented

Corrosion at the rear subframe and arch seamsE9x chassis€300–€2,000

Bubbling at the rear arch lip, scaling on subframe mounting points and rear suspension components. Age plus road salt. This generation isn't a notorious rotter, but nothing from 2005–2013 is immune in a salted market.

Check: Put it on a lift and look at the rear subframe mounting points and the arch lips from behind. Largely a non-issue on cars from southern Europe, a real one on northern and Baltic cars.

Body & corrosionoccasionalDetectable at viewingevidence: documented

Footwell module (FRM) failureE9x chassis€150–€700

Headlights, indicators, windows, wipers and central locking stop working at once, usually right after a battery change or a jump start. The module's memory corrupts when supply voltage dips. It is the single most common electrical failure on this generation.

Check: Test every window, both mirrors, the wipers, all exterior lights and the central locking before you drive. If any cluster of these is dead, this is why.

ElectricalcommonDetectable at viewingevidence: documented

Rear shock mount wearE9x chassis€250–€500

Knock from the rear over speed bumps, a hollow thump from the boot area. The rubber mounts perish. On hard-used cars the mount can crack the surrounding turret metal, which is a far bigger job.

Check: Lift the boot floor and look at the top of the shock towers for cracking or a lifted mount. Listen for a knock over bumps.

SuspensioncommonDetectable at viewingevidence: documented100–180k km

Ranked by probability × repair cost, not by how loudly a failure is discussed. Inherited from the engine, gearbox, chassis and shared components, each written once. All 14 issues in full →

Mileage and servicing

What the odometer does and doesn't tell you here, plus the service items whose neglect causes the expensive failures above.

These were long-distance cars and high mileage is normal and fine. So budget for the oil cooler seals somewhere past 200,000 km rather than treating them as a fault.

Service item	Interval	Cost
Engine oil Long-life intervals are hard on a V6 diesel that idles	20,000 km or annually	€150–210
Oil cooler seals Labour dominates and it worsens slowly	inspect from 180,000 km	€900–1,600
Gearbox oil and filter 510 Nm through a 7G-Tronic	80,000 km	€450–650

What to pay

What this engine sells for, against the median of every engine in the chassis. All figures are illustrative placeholders. See the basis chips.

median €9.2k

€5.0k€7.0k€16k

Cheapfind the reasonGood buyif it checks outFairnormal moneyOverpricedneeds justifying

Asking price (€)Mileage (km)

Enter an asking price to get a verdict against this variant's band: cheap, fair, good buy or overpriced.

United States vs Europe

1 EUR = 1.08 USD · 2026-07

🇪🇺 Europe · EUR€6,950band €5,050–€16,000

🇺🇸 United StatesNot soldC 320 CDI OM642 was never a US-market car

What that meansNo US band exists to compare. Any car you find there's a private import, parts and specialist knowledge are thinner, and the price says more about import cost than about the market.

US figures are the EU band converted at a stated rate. No US market differential is modelled: we hold no sourced US asking prices, and inventing one would be worse than saying so. What the comparison does show for real is availability. Most of this range was never sold in the US.

ModelMercedes-Benz C-Class C 320 CDI
ChassisS204
EngineOM642
Years2008–2011
MarketCentral EU
Windowrolling 12 months to 2026-07

Good buy at or under the marker · Median asking price · bar spans the 10th to 90th percentile · dashed line is the s204 median, all 4 engines

Good buy isn't the same as cheapest. The good-buy figure assumes the known failure items are either done with receipts or verifiably not yet due. Full breakdown by facelift phase →

Buyer notes

Our judgement, kept separate from the records it's built on.

Our read, not a record

The V6 diesel is the quietest and most relaxed way to own a W204, and the engine itself is close to indestructible. What it asks for is money at intervals: the oil cooler sits in the vee under the intake and its seals harden, and the swirl-flap linkage wears. Neither is complicated, both are labour-heavy, and both arrive around the same mileage. Then buy one with a thick history, look for oil down the back of the block, and price the work in rather than hoping.

Everything above this line comes from the issue and specification records. This paragraph is our judgement on top of them. See how we reach it.

Full specification

Manufacturer figures for this engine and body, as recorded in the variant and engine data.

Engine code	OM642 3.0 V6 CDI
Configuration	V6, turbocharged · 2987 cc
Fuel / injection	diesel · common rail
Model years	2008–2011
Facelift phase	Sold either side of the 2011 facelift, 2008–2010 pre, 2011 LCI
Power / torque	224 PS · 510 Nm
Transmissions	7-speed automatic (7G-Tronic)
Gearbox families	7G-TRONIC
Drivetrain	RWD
Economy (real-world)	6.5–8.5 l/100 km mixed
Markets	EU

C 320 CDI OM642

Overview

Pre-facelift or facelift, this engine spans both

Known issues, ranked by expected cost

Pre-purchase inspection

1Static checksEngine off, ideally on a lift.

2On the driveInclude low-speed manoeuvring, not just an open road.

3PaperworkOn these cars the folder is most of the value.

4OBD scanMandatory. A seller who refuses a scan has answered the question.