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Mercedes OM626 Engine (1.6 L Diesel, W205 C‑Class 2014–2018)
The OM626 is Mercedes‑Benz’s 1.6 L inline‑4 rear‑wheel‑drive diesel engine (also known as Renault R9M), powered by common‑rail injection up to 1,600 bar, VTG turbocharger, and advanced EGR/SCR systems to meet Euro 6 emissions standards
The OM626.951 is part of the OM626 family and is known for its balance of fuel efficiency and moderate power output, making it ideal for city driving and light-duty use. Despite its small displacement, it delivers respectable torque for daily performance.
While it’s appreciated for its economy and compact design, some common concerns include EGR-related carbon buildup and DPF clogging over time both manageable with regular maintenance and diesel system cleaning.
In this article, we’ll break down its strengths, known issues, and everything you need to know before trusting it under your hood.
Engine Specifications
The displacement of the four – cylinder in-line engine is 1598 cc with a bore of 80 mm and a stroke of 79.5 mm, with a cylinder spacing of 88 mm. The crankcase of the engine is made of gray cast iron, the cylinder head of an aluminum alloy.
The OM 626 and Renault R9M are among the world’s first passenger car diesel engines with steel pistons instead of aluminum pistons. Steel pistons with reduced-tension piston rings from the supplier Mahle are used.
Steel pistons are said to bring advantages in terms of fuel economy and strength over aluminum pistons thanks to lower friction and better thermal behavior. The charge cycle is controlled by four valves per cylinder ( four-valve technology ) and two overhead camshafts ( DOHC ).
The engine has an exhaust turbocharger with variable turbine geometry . The turbine wheel of the VTG loader is 37.5 millimeters in diameter smaller than the compressor wheel with 45 millimeters in diameter.
The adjustment of the guide vanes takes over a vacuum box, which is controlled via an electropneumatic pressure transducer from the engine control unit. Furthermore, the engine has a cooled low-pressure exhaust gas recirculation (EGR) .
The exhaust gas is removed behind the particle filter, cooled and re-introduced before the compressor.
Exhaust gas aftertreatment takes place with the aid of an SCR system .The common-rail injection works with a fuel pressure up to 1600 bar.
Key specifications:
- – Displacement: 1.6 liters
- – Power: 114 horsepower
- – Torque: 192 lb-ft
- – Configuration: Inline-4
- – Fuel System: Common rail direct injection
- – Emissions: Euro 6 compliant
Design and Features
The OM 626 engine’s design and architecture are a testament to Mercedes-Benz’s commitment to innovation and excellence. Featuring an all-aluminum construction, the engine is lightweight yet robust. The common rail direct injection system ensures precise fuel delivery, enhancing both performance and fuel economy.
Advanced features include:
- – Variable geometry turbocharger for optimal boost control
- – Start/stop system to reduce idle fuel consumption
- – Low-friction components to minimize internal losses
- – Advanced emission control technologies, including a diesel particulate filter (DPF) and selective catalytic reduction (SCR) system
OM626 engine problems & Troubleshooting
While the OM626 Engine is known for its reliability, some common issues have been reported by users. These include EGR valve blockages, DPF clogging, and occasional turbocharger failures. Regular maintenance and timely interventions can mitigate these problems, ensuring the engine runs smoothly.
| Problem | Symptoms | Recommended Action |
|---|---|---|
| EGR Valve Blockage | Loss of power, poor acceleration | Clean or replace EGR valve regularly |
| DPF Clogging | Limp mode, rough running | Use extended motorway driving; schedule professional regeneration |
| Turbo / Seal Failures | Oil in intake, smoke, limp mode | Inspect turbo, charge pipes, PCV separator; replace failed seals or hoses |
| Oil Leaks (valve cover) | Oil visible on hood or intake hoses | Check valve cover gasket & breather system; replace if faulty |
| Carbon Build‑up | Throttle flat spots, rough idle | Clean head/intake passages (e.g., walnut-blast) periodically |
Loss Of Power In Car While Driving : Case Study & Solution
Maintenance & Care Insights
- – Use quality synthetic oil, follow recommended intervals: every 15–20 k km, especially if tuned.
- – Regularly inspect EGR, DPF and turbo system, especially if used in urban stop‑go driving.
- – Avoid oil leaks by inspecting gasket and crankcase ventilation assembly.
- – Owners report limp mode issues often stem from EGR blockage or turbo/PCV leakage address early for reliability
Fuel Efficiency and Emissions
The OM626 Engine is designed with fuel efficiency and low emissions in mind. It achieves an impressive fuel economy of around 50 mpg, depending on the driving conditions and vehicle model. The engine’s compliance with Euro 6 emission standards underscores its environmental friendliness.
Fuel efficiency highlights:
- – Combined fuel economy: Approximately 50 mpg
- – CO2 emissions: Around 104 g/km
- – Technologies: Start/stop system, low-friction components, advanced combustion process
Applications and Models
The OM626 engine powers several Mercedes models, including the C-Class. Its versatility and performance make it a preferred choice for compact and mid-sized vehicles, providing a balanced blend of power and efficiency.
Models equipped with the OM626:
Comparison with other Mercedes diesel engines:
OM626 vs. OM654: The OM654 offers higher power output and improved efficiency, making it suitable for larger vehicles.
OM626 vs. OM651: The OM651 is a predecessor with similar performance but lacks some of the advanced features found in the OM626.
Conclusion
The OM626 Engine is a testament to Mercedes-Benz’s engineering prowess, offering a blend of performance, efficiency, and reliability. By understanding its specifications, common issues, and maintenance tips, owners can ensure their OM626 engine continues to perform at its best.
Whether you’re a current owner or considering a Mercedes model equipped with this engine, the OM626 is a worthy choice that delivers on multiple fronts.
Frequently Asked Questions
Which models use the OM626 engine?
The 1.6 L OM626 is fitted in W205 C‑Class C180/C200 BlueTEC diesel models (2014–2018).
Is OM626 a reliable engine?
Yes, provided service intervals are respected. Early EGR cleaning and leak checks are key.
Why does the car go into limp mode without fault light?
Often due to oil entering intake/turbo system or exhaust gas temperature sensor errors causing power reduction without MIL.
How can I prevent carbon build‑up?
Use clean fuel, perform periodic head/intake cleaning, especially with urban or cyclical use.
What causes oil in intake hoses?
Typically a faulty PCV or charge‑air hose seal inspect turbo inlet and breather system.
