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Mercedes-Benz M273 V8 Engine (2005–2013) – Overview, Common Issues & Maintenance Guide
M273 engine is a naturally aspirated V8 developed by Mercedes-Benz and produced from 2005 to 2013 as the successor to the M113 engine. With a focus on refinement, smoother power delivery, and updated technology, the M273 brought improvements such as variable valve timing and an all-aluminum construction.
It was engineered to deliver strong, linear performance while maintaining the luxurious driving experience expected from Mercedes sedans and SUVs.
M273 served as a transitional powerplant before the shift to turbocharged engines like the M278. It powered a range of models including the S-Class, E-Class, CLS W218, G-Class and GL-Class, offering a reliable and engaging V8 experience. While generally robust, the M273 is known to develop some common issues over time, such as intake manifold failures and camshaft adjuster wear.
In this article, we explore the engine’s specs, performance characteristics, typical problems, and maintenance tips to help owners keep it running smoothly.
The M273 was available in two main displacements:
- – 4.7L (M 273 E47)
- – 5.5L (M 273 E55)
In this article, we’ll explore the engine’s specifications, common issues, reliability, and the models it powers, along with practical maintenance tips for owners.
Engine Variants & Specs
The M273 engine is a 90-degree V8 featuring variable camshaft timing (VCT) and aluminum alloy construction for both the block and cylinder heads. This design prioritizes a balance of power and fuel efficiency.
| Variant | Displacement | Power | Torque | Years |
|---|---|---|---|---|
| M273 KE47 | 4.7 L V8 | ~340 PS | ~460 Nm | 2006–2010 |
| M273 KE55 | 5.5 L V8 | ~388 PS | ~530 Nm | 2006–2011 |
Built with aluminum block and heads, DOHC with VVT, and a magnesium intake manifold with variable flaps
Key specifications:
- – Engine Layout: V8, naturally aspirated
- – Displacement: 4.7L or 5.5L
- – Compression Ratio: 10.7:1 (E47) / 10.5:1 (E55)
- – Fuel Injection: Port injection
- – Power Output:
- -> E47: 340 hp and 460 Nm of torque
- -> E55: 388 hp and 530 Nm of torque
- – Max RPM: 6,500
- – Cooling System: Water-cooled with an electric fan
The engine’s power delivery is smooth, making it ideal for luxury vehicles focused on comfort and effortless acceleration.
M273 engine problems & How to Address Them
While the M273 engine is reliable in many respects, several known issues can arise over time, especially as mileage increases. Understanding these problems can help owners prevent major failures.
| Issue | Symptoms | Diagnosis & Fix | DIY? |
|---|---|---|---|
| Faulty timing chain idler sprocket | Ticking noise early (~60–80k mi), check-engine | Inspect guides; replace sprocket if early production — VIN check recommended | Pro |
| Cam plug oil leaks (< Jun ’08) | Oil pooling, low level, white smoke | Replace plastic cam plugs with revised metal ones post‑2008 | Partial |
| Intake manifold VVT flap failure | Rough idle, loss of power, CEL codes P2004/P2006 | Inspect manifold flaps and actuators; consider metal linkage repair kits or manifold replacement | DIY-check |
| Imbalanced shaft issues | Vibration, performance loss | Check sprocket wear; replace with updated part. Rare in later engines | Pro |
| Idle gear / throttle body malfunctions | Fluctuating RPM, rough idle | Clean throttle body, inspect idle gear mechanism | DIY |
M273 engine reliability
The M273 engine is considered reliable, with many units exceeding 200,000 km with proper maintenance. However, like most Mercedes engines of its era, it requires timely upkeep.
Strengths:
- – Smooth, linear power delivery.
- – Long service life with routine maintenance.
- – Minimal electronics compared to modern engines.
Weaknesses:
- – Prone to oil consumption.
- – Plastic intake manifold components can fail.
- – Timing chain issues may surface around 150,000 km.
With the right care, the M273 can be a dependable engine, particularly if known issues are addressed early.
Models Equipped with the M273 Engine
The M273 engine powered several high-end Mercedes-Benz models across the sedan, coupe, and SUV lineups. Below are the key models that came equipped with this engine:
M273 E47 (4.7L V8)
ML450 (W164)
M273 E55 (5.5L V8)
CL550 (C216)
M273 vs M278 : Key Differences
The M273 engine was eventually replaced by the M278 engine, which introduced significant advancements, especially in fuel efficiency and emissions. Here are the key differences between the two:
| Feature | M273 Engine | M278 Engine |
|---|---|---|
| Fuel Delivery | Port Injection | Direct Injection |
| Forced Induction | None (Naturally Aspirated) | Twin-Turbocharged |
| Power Output | 340-388 hp | 402 hp (on average) |
| Emissions | Higher | Lower (Eco-friendlier) |
| Fuel Economy | Less efficient | Improved fuel consumption |
The M278’s switch to twin-turbocharging and direct injection allowed for better performance and efficiency, making it more suitable for modern driving standards.
Maintenance Tips for M273 Owners
For M273 owners, following a preventive maintenance schedule is essential to avoid costly repairs. Here are some key tips:
- – Oil Changes: Every 8,000 – 10,000 km to prevent sludge buildup. Use the recommended 5W-40 synthetic oil.
- – Timing Chain Inspection: After 150,000 km, listen for rattles and inspect for wear.
- – Coolant System: Regularly check for leaks around the thermostat and water pump.
- – Intake Manifold: Inspect for rough idle and performance issues; replace worn components proactively.
Maintaining a log of services and inspections will also help keep the engine running smoothly for years to come.
Conclusion
The Mercedes M273 engine remains a solid choice for those who appreciate the smooth performance of a naturally aspirated V8.
Although the engine has a few known issues such as oil consumption and timing chain wear many of these can be managed through regular maintenance.
For enthusiasts who prioritize a classic V8 driving experience over turbocharged power, the M273 offers a blend of luxury, reliability, and performance.
Frequently Asked Questions
Is the M273 engine reliable?
Generally yes, it’s robust and long-lasting when regularly maintained. Only timing idler sprocket and manifold VVT flaps are known wear points.
When should I replace the timing idler sprocket?
If the engine model is from 2006–2008 or has early VIN, replace the sprocket by 80 000 mi to prevent chain wear.
What’s the fix for intake manifold flap issues?
Repair kits with metal linkages often fix flap faults. Severe cases may require full manifold replacement (~€800+).
Can I drive with rough idle from idle gear failure?
Yes, but it can lead to stalling or poor performance. Cleaning or replacing the idle control gear resolves the issue.
