Mercedes-Benz E550 Engine Crankcase Vent Valve: A Complete Guide (2007-2017)
Don't let a bad vent valve cause oil leaks or rough running on your E550's V8 engine.
- First, confirm your E550's model year to determine if you have the M273 (2007-2011) or M278 (2012-2017) engine, as the parts are different.
- A key symptom for the M273 engine is an oil leak at the back of the engine, while a hissing sound is common for the M278.
- Replacement on the 2012-2017 M278 engine is significantly more difficult than on the earlier M273 engine.
- For a labor-intensive job, choosing a higher-quality aftermarket brand like CRP/Rein over a budget brand may prevent premature failure.
Is This the Right Part for Your E550? Check Your Engine
Before buying a crankcase vent valve, you must know which V8 engine is in your 2007-2017 Mercedes-Benz E550. The part is different depending on the year.
- 2007-2011 E550: These models have the naturally aspirated M273 engine. The part is a larger assembly often called an "oil separator" located on the back of the passenger-side cylinder head. A common failure sign is an oil leak down the back of the engine.
- 2012-2017 E550: These models have the twin-turbocharged M278 engine. The part is a smaller, round valve tucked tightly against the firewall. A key symptom of failure is a distinct hissing sound at idle.
Check Your Engine Before You Buy
Ordering the wrong part is a common mistake. The M273 and M278 vent valves are not interchangeable. Verify your vehicle's year and engine to ensure you purchase the correct component.
Symptoms of a Failing Crankcase Vent Valve
A bad vent valve can cause a range of problems. While some symptoms are shared between the two engine types, others are specific.
- Check Engine Light: A failing valve can trigger fault codes, most commonly P052E, which relates to crankcase ventilation performance.
- Rough Idle or Misfires: The engine may run poorly or stumble at idle because the valve is allowing unmetered air into the intake manifold.
- Increased Oil Consumption: If the valve fails to separate oil from the crankcase gases, your engine may start burning oil.
- Oil Leaks (M273): For the 2007-2011 E550, the most common sign is oil leaking from the separator housing onto the exhaust, causing a burning smell.
- Hissing Noise (M278): For the 2012-2017 E550, a loud hissing or whistling sound from the back of the engine at idle points to a torn diaphragm inside the valve.
Choosing the Right Aftermarket Part
When replacing the crankcase vent valve, you have options ranging from budget-friendly to OE-quality. For a part that requires significant labor to replace, especially on the M278 engine, choosing a quality brand can save you from doing the job twice.
Brand Quality Tiers:
- CRP (Rein): Often considered an OE supplier, CRP/Rein parts are known for high-quality materials and precise fitment, making them a reliable alternative to Genuine Mercedes parts.
- Vaico: A German aftermarket brand that is generally seen as a solid, mid-tier option for many European vehicle parts.
- URO Parts: This brand is typically the most affordable. While suitable for some non-critical repairs, forum discussions show mixed reviews regarding the quality and longevity of their engine components. For a hard-to-reach part, the risk of premature failure may outweigh the initial cost savings.
Pro-Tip: Consider a Kit
The plastic hoses connected to the vent valve become brittle over time and can easily break during replacement. It is often a good idea to purchase a kit that includes the valve and all related breather hoses to do a complete and lasting repair.
Cost of Replacing the Engine Crankcase Vent Valve
| Part Type | Price Range |
|---|---|
| New OEM | $150 - $250 |
| New Aftermarket | $35 - $80 |
| Shop Labor | $150 - $450 |
Frequently Asked Questions (FAQ)
Can I just replace the diaphragm inside the valve?
While some repair kits exist for just the rubber diaphragm, it is generally not recommended. The plastic housing of the valve also becomes brittle with age and can crack. Replacing the entire valve assembly is the most reliable repair.
What happens if I don't replace a bad vent valve?
Ignoring a failed vent valve can lead to more serious issues. Continued high crankcase pressure can force oil out of other seals, like the rear main seal, leading to expensive repairs. It can also cause persistent check engine lights, failed emissions tests, and poor engine performance.
Is the replacement DIY-friendly?
For the 2007-2011 E550 (M273), it is a manageable DIY for someone with moderate experience, though access is tight. For the 2012-2017 E550 (M278), the job is much more difficult due to the valve's location against the firewall and is recommended for experienced DIYers or a professional shop.
Are there any recalls for this part?
No active recalls were found for the crankcase vent valve on the 2007-2017 Mercedes-Benz E550. While Mercedes has issued warranty extensions for a similar issue on other models with 4-cylinder engines, this does not apply to the E550's V8 engines.
Technical Specifications
OEM Part Numbers: A2720100631 2720100631 A2780100431 2780100431
The correct part depends on the engine. The 2007-2011 E550 with the M273 engine uses part number A2720100631. The 2012-2017 E550 with the M278 engine uses part number A2780100431 or a related kit.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mercedes-Benz E550:
- 🛍️ Shop This Part
- Is This the Right Part for Your E550? Check Your Engine
- Check Your Engine Before You Buy
- Symptoms of a Failing Crankcase Vent Valve
- Choosing the Right Aftermarket Part
- Pro-Tip: Consider a Kit
- Cost of Replacing the Engine Crankcase Vent Valve
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off