EXPERT IN AUTO PARTS
19 March 2025 Table of content
The timing chain in the CGI engines (e.g. C180 CGI 156 hp) is one of the W204's most serious weak points. From 120,000-150,000 km, affected vehicles exhibit rattling noises during cold starts, error messages such as "P0016" (camshaft position) and, in extreme cases, engine damage due to the chain jumping. Causes include worn tensioning slides, defective chain guides or insufficient lubrication.
A systematic check is critical in order to avoid consequential damage. The Mercedes W204 CGI timing chains require an inspection of the tensioners and guides every 60,000 km. If the first knocking noises are heard, the chain and tensioner should be replaced immediately - according to forum reports, a repair costs from €1,500. As a preventive measure, we recommend changing the engine oil every 15,000 km with MB 229.5-certified oils.
A common electronic fault in the W204 concerns the ignition lock ("Keyless Go") or key recognition. Affected drivers report that the key is not recognized ("Key not found" message) or that the immobilizer blocks starting. Defective antenna rings around the ignition lock, flat car key batteries or software errors in the EIS control unit are often responsible.
Professional maintenance is essential. The Mercedes W204 key recognition systems require diagnostics with a STAR scanner to read out error codes such as "9021" (antenna) or "9055" (ELV communication). According to the MB forum, replacing the antenna rings or updating the software of the EIS module solves most cases. In the case of mechanical defects in the ignition lock, the entire module must be replaced.
Turbocharger failures occur particularly in the diesel variants (e.g. 220 CDI with OM651 engine) from 150,000-180,000 km. Typical symptoms are black smoke when accelerating, oil residue in the charge air hose and error codes such as "P0299" (lack of vacuum). The cause is usually a lack of oil due to clogged supply lines or worn bearings.
Article number: 529 0115 10
£ 67,71
price incl. 20% VAT, excl. delivery costs
-18%
FEBI BILSTEIN Gearbox service kit
with gasket/seal, with seal ring, with bolts/screws, with a plug
Article number: 171748
compared to
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£ 129,99
£ 105,97
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BOSCH Water Pump, parking heater
12V, without holder
Article number: 0 392 023 004
£ 53,34
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-5%
Article number: MN7501-10
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£ 32,53
£ 30,84
£ 3,08 for 1 litre
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Article number: VE18320
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£ 24,39
£ 24,39 for 1 litre
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A professional inspection is crucial here. Mercedes W204 turbochargers require regular oil changes (every 15,000 km) and inspections of the charge air ducts. If there is a loss of power, the boost pressure should be measured - values below 1.2 bar indicate defects. According to garages, replacing the turbocharger costs from €2,000, with used injection pumps often failing again after 80,000 km.
The "won't start" problem is often caused by the electronic immobilizer (ELV). Affected vehicles display a message such as "Immobilizer activated - engine start not possible". Software conflicts in the EIS control unit, defective batteries in the key or communication errors with the ELV module are responsible.
Regular maintenance can prevent this. The Mercedes W204 immobilizer control units require updates in accordance with MB Technical Service Bulletin LI54.10-P-059875. In the event of sporadic failures, a restart often helps: hold the key in position 2 for 30 seconds, then start. Persistent failure requires replacement of the ELV control set.
Defects in the instrument cluster (speedometer/display) are manifested by failing displays, flickering LEDs or error messages such as "Vehicle not ready to drive". This occurs particularly in models from 2009 onwards after 100,000-130,000 km. The cause is cold solder joints on the circuit board or voltage drops due to ageing capacitors.
A thorough diagnosis is essential here. The Mercedes W204 instrument cluster can often be repaired using repair kits with new capacitors and soldering work. A software reset using the STAR diagnostic tester can rectify temporary faults. As a preventive measure, it is advisable to avoid voltage peaks caused by defective batteries.
Mercedes W204 models have been affected by several recalls for airbag problems, including the Takata airbag crisis. These issues can lead to unintended airbag deployments and require prompt inspection. Symptoms often include unintended airbag deployments or a warning light on the dashboard.
Regular maintenance is essential to detect these problems at an early stage. Mercedes W204 airbags and safety systems require regular checks and, if necessary, replacement of faulty components to ensure the safety of the vehicle. An expert inspection can help to identify and rectify such problems before they lead to major damage.
BREMBO Brake disc
295x28mm, 5, perforated/vented
Article number: 09.A613.51
£ 42,51
Price per item
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Article number: MN7715-10
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£ 40,53
£ 4,05 for 1 litre
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-19%
Article number: MN7511-4
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£ 19,34
£ 15,66
£ 3,92 for 1 litre
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BREMBO Brake disc
360x36mm, 5, internally vented, slotted/perforated, two-part brake disc
Article number: 09.9764.23
£ 317,40
Price per item
price incl. 20% VAT, free delivery
-21%
Article number: MN7511-5
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compared to
RRP
£ 21,98
£ 17,28
£ 3,46 for 1 litre
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Based on feedback from owners, the following problems can occur:
| Strengths | Weak points |
|---|---|
| Robust body and chassis | Timing chain problems with CGI engines |
| High-quality interior | Turbocharger defects in CDI models |
| Good driving performance (e.g. 220 CDI) | Electronic faults in the ignition lock/combination |
| Long service life for diesel models | Immobilizer problems |
| Low depreciation | Susceptible transmission oil cooler (7G-TRONIC) |
Conclusion
The Mercedes W204 impresses with its solid build quality and comfort, but shows weaknesses in certain components such as the timing chain or turbochargers. Regular maintenance and early repairs are crucial to avoid high follow-up costs. Mercedes W204 electronic components such as the ignition lock or instrument cluster require special diagnostic procedures. With preventive measures, the W204 will nevertheless remain a reliable companion.
OPEL GM Engine oil
10W-40, 5l, Part Synthetic Oil
Valvoline Engine oil
5W-30, 4l
MOBIL Engine oil
5W-30, 5l
MANNOL Engine oil
5W-30, 4l
BOSCH Tyre pressure sensor (TPMS)
GATES Radiator hose
EPDM (ethylene propylene diene Monomer (M-class) rubber)
MANNOL Engine oil
5W-40, 5l
BILSTEIN Coil spring
Front Axle
FEBI BILSTEIN Shaft Seal, differential
Rear Axle, both sides
BOSCH Handbrake shoes
with accessories