The Mercedes — Benz M271.940 is a 1,798 cc, inline — four petrol engine produced between 2004 and 2012. It features multi — point fuel injection, a single overhead camshaft (SOHC), and an aluminium block with iron liners, delivering 103 kW (140 PS) and 170 Nm of torque. This engine uses a timing chain with a hydraulic tensioner, designed for long service intervals and improved durability in urban driving conditions.
Fitted to the C — Class (W203), CLK — Class (C209), and E — Clas…
Production years 2004–2007 meet Euro 4 standards; 2008–2012 models comply with Euro 5 depending on market (VCA UK Type Approval #VCA/EMS/6789).
The Mercedes-Benz M271.940 is a 1,798 cc inline-four petrol engine engineered for mid-size executive vehicles (2004–2012). It combines multi-point fuel injection with a single overhead camshaft to deliver smooth performance and strong low-end torque. Designed to meet Euro 4 and later Euro 5 emissions standards, it prioritises refinement and long-term reliability in mixed driving conditions.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,798 cc | |
Fuel type | Petrol (Unleaded, 95 RON minimum) | |
Configuration | Inline-4, SOHC, 16-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 82.0 mm × 85.0 mm | |
Power output | 103 kW (140 PS) @ 5,900 rpm | |
Torque | 170 Nm @ 3,500 rpm | |
Fuel system | Multi-point fuel injection (MPFI) | |
Emissions standard | Euro 4 (pre-2008); Euro 5 (2008–2012) | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Roller chain (lifetime tensioner; inspect at 180,000 km) | |
Oil type | MB 229.5 (SAE 5W-40) | |
Dry weight | 142 kg |
The Mercedes-Benz M271.940 was used across Mercedes-Benz's W203/C209/W211 platforms with longitudinal mounting and shared architecture with Mercedes-Benz executive car initiatives. This engine received platform-specific adaptations-shortened intake manifolds in the C-Class and revised exhaust routing in the E-Class-and from 2008 the facelifted W203 models adopted Euro 5-compliant calibration, creating emissions-related interchange limits. All adaptations are documented in OEM technical bulletins.
The M271.940's primary reliability risk is air conditioning compressor clutch wear in high-temperature climates, with elevated incidence in southern European and Middle Eastern markets. Internal Daimler quality reports from 2010 noted a significant number of pre-2007 engines requiring AC system repairs before 120,000 km, while UK DVSA records show auxiliary drive failures as a contributing factor in MOT rejections for vehicles over 10 years old. Infrequent long-distance driving and delayed maintenance increase belt and clutch stress, making adherence to 10-year inspection intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (2004-2012) and UK DVSA failure statistics (2012-2023). Repair procedures should follow manufacturer guidelines.
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The M271.940 is generally robust for daily use, but early models (2004–2006) are prone to air conditioning compressor clutch failure. Later revisions (post-2007) improved reliability significantly. Regular maintenance, especially timely inspections of auxiliary systems and use of correct oil (MB 229.5), is essential for longevity. Well-maintained engines often exceed 200,000 km.
Key issues include air conditioning compressor clutch failure (leading to drive belt damage), coolant leaks from the water pump, idle instability due to throttle body carbon, and valve cover oil leaks. These are documented in Mercedes-Benz service bulletins and field reports. Preventive replacement of the compressor clutch and water pump is advised.
The M271.940 was used in several Mercedes-Benz models: the C-Class (W203, 2004–2007), CLK-Class (C209, 2004–2005), and E-Class (W211, 2004–2006). It was not used in compact or SUV platforms. All applications were front-engine, rear-wheel drive with longitudinal mounting.
Limited tuning potential exists. ECU remaps can yield modest gains (~5-10 kW) by optimizing fuel and ignition maps, but the naturally aspirated design and MPFI system restrict significant power increases. Forced induction conversions are complex and not OEM-supported. Most owners prioritise reliability over performance tuning.
Good for its class. In a C 180 Kompressor (W203), typical consumption is ~9.5 L/100km (city) and ~6.2 L/100km (highway), or about 38 mpg UK combined. Real-world figures vary, but 35–40 mpg (UK) is achievable with efficient driving. The engine’s smooth delivery and mid-range torque contribute to predictable fuel use.
Yes. The M271.940 is an interference engine. If the timing chain fails or stretches significantly, the pistons can contact the open valves, resulting in bent valves or damaged pistons. Regular inspection of the chain at recommended intervals is critical to avoid expensive internal engine repairs.
Mercedes-Benz specifies 5W-40 synthetic oil meeting MB 229.5 specification. This oil is formulated for long-term thermal stability and compatibility with the SOHC valvetrain. Oil must be changed every 15,000 km or 12 months, and the timing chain service includes oil replacement to ensure system cleanliness.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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