Known faults for the Mercedes-Benz Clase C (W204).

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.

Sources from the original database

Engine / equipment

M271 1.8 Kompressor / CGI (C 180/200 W203 and W204, E 200 W211/W212, CLK 200, SLK 200)

Period mentioned

2002–2015

Symptoms

Rattle for 2–3 seconds or more on a cold start; engine light for camshaft timing deviation.

Possible cause described

A single-row chain that stretches and cast-iron camshaft adjusters whose teeth wear. On later versions the hydraulic tensioner fails more often.

Check for the garage

Listen to a cold start, read timing fault codes and check the chain replacement history.

Cost cited in the source

€1,500–3,000A rough figure from the original database, not an up-to-date quote.

Sources from the original database

Engine / equipment

OM646 2.1/2.2 CDI (C 200/220 CDI W203 and W204, E 200/220 CDI W211, Vito, Sprinter) and the 2.2 CRD in the Chrysler PT Cruiser

Period mentioned

2002–2010

Symptoms

Puffing or “chuffing” at idle, a diesel smell under the engine cover and a hard black crust around the injectors; power loss from sooted intake flaps or turbo.

Possible cause described

The copper washer under each injector fails and combustion gases escape, carrying diesel and oil that harden into a black crust (“black death”). Soot also seizes the intake flaps and turbo mechanism. Otherwise it is a very robust engine.

Check for the garage

Remove the engine cover and look for black residue around the injectors, listen at idle and check the intake flaps.

Cost cited in the source

Injector washers: approx. €200–800 depending on how advanced the crust isA rough figure from the original database, not an up-to-date quote.

Mileage cited in the database: from 150,000 km. This is not a maintenance interval and does not predict a failure.

Sources from the original database

Engine / equipment

OM651 2.1/2.2 CDI (C 200/220/250 CDI, E 200/220/250, GLK, Vito, Sprinter)

Period mentioned

2008 onwards

Symptoms

Chain rattle on a cold start; on early units, loud injector knocking; coolant loss from the plastic coolant manifold or the EGR cooler.

Possible cause described

Plastic chain guide and a hydraulic tensioner that loses pressure (the chain is at the rear). Early units used problematic piezo injectors that Mercedes replaced in a campaign.

Check for the garage

Listen to a cold start, check the dealer's injector campaign history and check the coolant level.

Cost cited in the source

Chain: approx. €1,500–3,000 (estimate)A rough figure from the original database, not an up-to-date quote.

Sources from the original database

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.

Sources from the original database

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.

Sources from the original database

Engine / equipment

M156 6.2 V8 AMG (C 63 W204, E 63 W211 and W212 until 2011, CLK 63, CLS 63, ML 63, S 63 and CL 63 until 2010, SL 63)

Period mentioned

2006–2015

Symptoms

Coolant loss, coolant in the oil or white smoke (broken head bolts); rattle or ticking on start-up (camshaft and lifter wear).

Possible cause described

Cylinder head bolts that break on engines up to 2012 (Mercedes bulletin from 2011) and nodular cast-iron camshafts that wear together with the lifters, mainly on the intake side (bulletin from 2009).

Check for the garage

Overnight cooling system pressure test, oil analysis and camshaft inspection with a borescope.

Cost cited in the source

Major engine repair (several thousand euros)A rough figure from the original database, not an up-to-date quote.

Sources from the original database