Known faults for the Mercedes-Benz Clase C (W203).

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

722.6 five-speed automatic (5G-Tronic), not the 7G-Tronic: C-Class W203, E-Class W210 and W211, CLK, S-Class W220, ML W163, SLK, SL R230, Vito and Sprinter with this gearbox

Period mentioned

1996–2013

Symptoms

Oil around the electrical connector on the side of the gearbox, harsh shifts or slipping, delayed engagement and limp mode: the car stays in one gear (usually 2nd and reverse after a restart) and the engine light comes on.

Possible cause described

The plastic adapter of the 13-pin connector has O-rings that harden and let oil out. Oil can wick up inside the wiring to the gearbox control unit and damage it. If the problem persists after replacing the connector, there may be oil in the harness, a damaged wire or a conductor plate fault.

Check for the garage

Read the gearbox control unit codes before switching off if possible (a restart can clear them). Look for oil at the connector and, with it unplugged, on its pins and at the control unit plug. According to the service bulletin, the connector should only be removed with gearbox oil below 50 °C to avoid damaging the conductor plate, and the harness must be routed without tension.

Cost cited in the source

Connector adapter: about $15–20 in parts (US prices quoted in the sources), plus the lost fluid; labour extra. If oil has reached the control unit, the repair is bigger.A 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

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