All About the Mercedes M273 Engine
The Mercedes-Benz M273 engine is a naturally aspirated V8 that first appeared in 2005. It was introduced as a successor to the M113 engine, bringing improved technology and refinement. Known for its smooth power delivery and robust performance, the M273 was designed to power luxury sedans and SUVs within Mercedes’ lineup. This engine served as a bridge between the old-school, naturally aspirated V8s and the newer turbocharged designs like the M278.
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.
Technical Specifications
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.
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: 335 hp and 460 Nm of torque
- E55: 382 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.
Common Problems with the M273 Engine
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.
1. Timing Chain Issues
- Symptoms: Rattling noise during cold starts, check engine light (P0016 / P0017).
- Cause: The timing chain stretches or the guides wear down over time.
- Solution: Replace the timing chain, guides, and tensioners to avoid engine misalignment and damage.
2. High Oil Consumption
- Symptoms: Owners often report having to top off oil frequently between changes.
- Cause: Worn valve stem seals allow oil to leak into the combustion chamber.
- Solution: Replace the valve stem seals, ideally during a major service.
3. Intake Manifold Runner Flaps Failure
- Symptoms: Poor engine performance, rough idling, and fault codes related to the intake system (P2004 / P2005).
- Cause: Plastic runner flaps inside the intake manifold degrade with heat and time.
- Solution: Replace the intake manifold; aftermarket metal upgrades are available for better durability.
4. Coolant Leaks
- Symptoms: Coolant loss without visible leaks, overheating, or puddles under the car.
- Cause: Weak points around the thermostat housing and water pump.
- Solution: Regularly inspect and replace seals, thermostat, and water pump as needed.
Reliability: Is the M273 Engine Durable?
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 | 335-382 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.
With proper care, this engine can provide an enjoyable driving experience for many years, making it a favorite among Mercedes enthusiasts.
