Mercedes C-Class W204 (2007-2014) Reliability Guide
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The Mercedes C-Class W204 , produced from 2007 to 2014, is one of the brand's most popular premium sedans. It has won over customers with its comfort, understated style, and diverse engine options. This generation is also renowned for its superior reliability compared to the W203 it replaced.
But as always, some engines are preferable and others to avoid. Here's our Mercedes C-Class W204 reliability guide to help you choose the right used model.
Reliability of petrol engines
C180 / C200 CGI (1.8 Turbo – M271)
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Pleasant to drive , smooth and relatively fuel-efficient.
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Known weaknesses:
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Fragile timing system (faulty chain tensioner, rattling noise on cold start).
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Excessive oil consumption.
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Sensitive ignition coils and injectors.
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Preferably choose models from after 2010 , which have better reliability in terms of distribution.
C250 CGI (1.8 Turbo – M271)
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Same base as the C180/C200 but with more power (204 hp) .
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Same risks of oil consumption and distribution problems .
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Good compromise between performance and fuel consumption, but average reliability before 2010.
C350 (V6 3.5 – M272)
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A more refined and pleasant engine , offering superior torque and a pleasing sound.
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Known problems:
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Wear on the balance shaft pinion (especially before 2008) .
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Sensors and flow meter sometimes malfunction.
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After 2009, the engine became much more reliable and is an excellent petrol option.
C63 AMG (V8 6.2 – M156)
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Legendary engine , naturally aspirated and very mechanically robust.
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Points to be aware of:
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Premature wear of the cylinder heads and rocker arms on some examples.
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High oil consumption.
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Significant maintenance costs (spark plugs, brakes, oil, tires).
- When well maintained, it is a very durable and sought-after engine.
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Reliability of diesel engines
C200 CDI / C220 CDI / C250 CDI (2.1 – OM646 then OM651)
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OM646 (until 2009) : simple, reliable and durable engine.
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OM651 (after 2009) : more modern, but more complex and fragile.
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Common problems:
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Fragile injectors (especially on OM651).
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EGR/DPF valve fouling in urban use.
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Noisy timing chain.
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Preferred: OM646 before 2009 for reliability, OM651 for long and regular journeys (highway).
C320 CDI / C350 CDI (V6 3.0 – OM642)
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Excellent diesel engine , torquey, quiet and durable.
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Possible weaknesses:
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Oil leaks (rocker cover, crankcase).
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Wear of the swirl flaps (intake flaps).
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DPF pressure sensors sometimes fail.
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An excellent choice for high-mileage drivers or demanding drivers.
Electronic and transmission points
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7G-Tronic automatic transmission:
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Generally reliable if the oil is changed every 60,000 km .
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Monitor for jerking or slippage when hot.
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Electronics:
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ABS/ESP sensors, parking detectors and comfort modules sometimes malfunction.
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COMAND GPS and Audio 20 system subject to some software bugs.
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Front axle:
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Silent blocks and ball joints should be checked from 120,000 km.
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How to check known engine problems engine by engine
Before making any purchase, take the time for an extended test drive and a thorough inspection. Here's how to detect typical faults depending on the engine :
1.8 CGI (M271 – C180/C200/C250)
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Listen for a metallic noise when starting from cold (timing chain).
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Check the oil level and for any deposits under the cap.
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An irregular idle speed can indicate a worn injector or coil.
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Ideally, choose an engine from after 2010 , recognizable by the revised chain tensioner.
V6 3.5 (M272 – C350)
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A slight clunking noise at low engine speed may indicate wear on the balance sprocket.
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Engine warning light or loss of power: often related to the mass airflow sensor.
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The engine must run perfectly smoothly when hot, without vibration.
V8 6.2 (M156 – C63 AMG)
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Watch for any metallic rattling when cold: rocker arms or cylinder heads.
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Check oil consumption (blue smoke = worn piston rings).
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Require documented maintenance and frequent oil changes (<10,000 km).
2.1 CDI (OM646 / OM651 – C200 to C250 CDI)
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Diesel smell = leaking injector (often visible around the injector well).
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Noisy chain when cold on OM651 = low tension.
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Check that the DPF is not saturated (no orange engine warning light).
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Avoid repeated short trips with this engine.
3.0 CDI (OM642 – C320 / C350 CDI)
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Check for oil leaks under the engine.
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The idle speed should not vibrate : possible wear of the swirl flaps.
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Monitor any engine warning lights (often DPF sensor).
7G-Tronic Box
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No jerking or slippage should occur, whether the engine is cold or hot.
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Check the date of the last oil change (every 60,000 km).
Purchase recommendations
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Check the complete service history , ideally at a Mercedes dealership.
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Opt for a vehicle that has been serviced every 10,000 to 15,000 km , especially for turbo petrol engines.
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Inspect the engine compartment for any traces of oil, soot, or suspicious odor.
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For diesel vehicles , request an OBD reading to check the DPF regenerations.
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Automatic transmission: require a recent oil change invoice.
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Electronics: test all equipment (GPS, air conditioning, cruise control, parking sensors).
Verdict: Which Mercedes C-Class W204 should you choose?
The best choices:
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C220 CDI OM646 (up to 2009) : reliable, economical and durable.
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C350 V6 petrol : a noble and robust engine, without major additional maintenance costs.
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C350 CDI V6 : powerful, economical and very long-lasting.
To avoid:
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C180/C200 CGI before 2010 : fragile distribution and oil consumption.
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OM651 if frequent urban use (sensitive EGR and DPF).
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❓ FAQ – Used Mercedes C-Class W204
Is the Mercedes C-Class W204 reliable?
Yes, overall very reliable, especially compared to previous generations (W203, W202).
Which petrol engine should I choose?
👉 The 1.8 CGI , an excellent compromise between driving pleasure and fuel consumption.
Which diesel engine is the most reliable?
👉 The 2.1 CDI OM646 (up to 2009) and the 3.0 CDI OM642 are the most recommended.
Is the automatic transmission reliable?
👉 Yes, provided that the 7G-Tronic transmission is regularly drained every 60,000 km.
💡 In summary
The Mercedes C-Class W204 combines elegance, comfort and mechanical longevity.
By carefully choosing your engine and checking the sensitive points, you can enjoy a reliable and durable premium sedan for many years.
