KNOWN FAULTS · Mercedes-Benz

Known faults for the Mercedes-Benz Clase R (W251).

2006–2013 · Diesel / Petrol

Sources are not verified in real time and no entry confirms that your car is affected.

3 known faults with sources

Engines: R 280 / 300 / 320 / 350 CDI (OM642) (Diesel)

Oil cooler and injector leaksOil leaks / injectors

Engine / equipment: OM642 3.0 V6 CDI/BlueTEC (280/300/320/350 CDI, ML, GL, R, Sprinter)
Period mentioned: 2005 onwards
Symptoms: Oil pooling in the engine's V, burning oil smell, drips under the engine; or a hiss or chirp next to an injector with an exhaust smell.
Possible cause described: The oil cooler seals (in the engine's V) degrade. Separately, injector washers leak combustion gas and carbon builds up around the injector.
Check for the garage: Visual inspection of the engine's V and the base of the injectors.
Cost cited in the source: Oil cooler seals: labour-heavy, approx. €800–1,800 (estimate)A rough figure from the original database, not an up-to-date quote.

Engines: R 280 / 300 / 320 / 350 CDI (OM642) (Diesel) · R 350 (Petrol)

Applies if: Only if fitted with 7G-Tronic. Confirm the gearbox type.

7G-Tronic conductor plateGearbox

Engine / equipment: 7G-Tronic automatic gearbox (722.9) in the C, E, S-Class, ML, GL, SLK, Sprinter…
Period mentioned: 2004 onwards (more failures in 2004–2008)
Symptoms: Gearbox stuck in 2nd or 3rd (limp mode), harsh shifts, delay engaging D or R, gearbox warning often without an engine light; turning off and restarting clears it for a while.
Possible cause described: The conductor plate (the control unit with built-in speed sensors) fails from heat and vibration. Oil leaks through the 13-pin connector are also common.
Check for the garage: Diagnose with Xentry/STAR to see the sub-codes (a basic reader only shows P0700). Check for oil in the gearbox connector.
Cost cited in the source: Approx. €1,400–2,800 (estimate)A rough figure from the original database, not an up-to-date quote.

Engines: R 350 (Petrol)

M272 / M273 balance shaft sprocketTiming system

Engine / equipment: M272 V6 (280, 300, 350) and M273 V8 (450, 500, 550) in the C, E, CLK, CLS, SLK, ML, GL, R, S and CL
Period mentioned: 2004–2008 (engines below serial number 2729..30 468993)
Symptoms: Engine light with P0016 and P0017 (1200 and 1208 on Mercedes diagnostics), rattle on start-up, hesitation, misfires and, in severe cases, stalling.
Possible cause described: Balance shaft sprocket (M272) or timing idler gear (M273) made from metal that is too soft: the teeth wear, the chain goes slack and the timing slips. Mercedes changed the material in mid-2008.
Check for the garage: Compare the engine serial number with the 2729..30 468993 cut-off, read cam correlation codes and, if in doubt, inspect the sprocket with a borescope. First rule out the cam adjuster magnet (a cheap fault).
Cost cited in the source: Engine-out repair: over €3,700 (converted from dollars)A rough figure from the original database, not an up-to-date quote.