MERCEDES 139-078-34-00 Engine Crankcase Vent Valve GLC43 Benz

( Manufacturer Part Number: 139-078-34-00 ), ( Model: C43 C63 GLC43 SL43 ), ( Part Type: Valve Engine Vent ), ( Genuine Oem: Yes ), ( Manufacturer Warranty: 1 Year ), ( Universal Fitment: Direct Replacement ), ( Make: Mercedes-benz ), ( Year: 2023 2024 2025 ), ( Parts Included: Only Part Reference 0 On The Diagram Is Included ), ( Replaces Part Number: 1390782800 )

Review MERCEDES benz Genuine Engine Crankcase Vent Valve fits 2023–2025

The **Mercedes-Benz 139-078-34-00 Engine Crankcase Ventilation Valve** is a precision-engineered component designed to maintain optimal airflow and pressure regulation within the engine s crankcase system of select Mercedes-Benz vehicles, ensuring long-term reliability and performance. This critical valve plays a pivotal role in the **Positive Crankcase Ventilation (PCV) system**, which prevents the buildup of harmful blow-by gases comprising unburned fuel, oil vapors, and combustion byproducts that can degrade engine components over time. Crafted from high-quality materials, including durable plastic and reinforced elastomeric seals, the valve is engineered to withstand the demanding conditions of modern internal combustion engines, including high temperatures, pressure fluctuations, and exposure to lubricants.

The **139-078-34-00** is specifically tailored for compatibility with certain Mercedes-Benz models, including those equipped with inline-4 or inline-6 engines, where it interfaces seamlessly with the engine s oil filler cap or a dedicated vent line. Its design incorporates a **pressure-sensitive diaphragm or spring-loaded mechanism** that dynamically adjusts airflow based on engine operating conditions, allowing excess crankcase gases to escape while preventing contaminants from re-entering the combustion chamber. This two-way functionality not only enhances engine efficiency but also reduces emissions, aligning with stringent automotive regulations.

Over time, wear, clogging from oil residue, or failure of the valve s internal components can lead to symptoms such as **oil leaks, reduced engine performance, or the dreaded "check engine" light** due to improper PCV function. Replacing the valve with the **OEM-spec 139-078-34-00** ensures a direct fit and restores the crankcase ventilation system to its intended specifications, mitigating potential long-term damage to the engine s internals, such as piston rings, valve seals, or the crankshaft. For enthusiasts and mechanics alike, this valve represents a straightforward yet essential upgrade or replacement part, underscoring Mercedes-Benz s commitment to precision engineering and vehicle longevity.

The **Mercedes-Benz 139-078-34-00 Engine Crankcase Ventilation (PCV) Valve** is a critical component for maintaining proper engine breathing and reducing emissions. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of purchasing a 139-078-34-00 Engine Crankcase Vent Valve**

1. **Direct OEM Replacement** This is an original equipment manufacturer (OEM) part, meaning it is designed to match the specifications of the engine it was originally installed in. This ensures proper fitment, performance, and compatibility with the vehicle s emissions system.

2. **Reliability and Durability** OEM parts are built to withstand the conditions of the engine s environment, reducing the likelihood of premature failure compared to aftermarket alternatives that may not meet the same quality standards.

3. **Emissions Compliance** The PCV valve plays a key role in controlling crankcase pressure and routing blow-by gases to the intake manifold for combustion. A faulty valve can lead to emissions failures (e.g., failing an OBD-II test), so replacing it with an OEM part ensures the vehicle continues to meet regulatory standards.

4. **Prevents Engine Damage** A failing PCV valve can cause excessive crankcase pressure, leading to leaks in gaskets, seals, or even damage to the valve cover or oil filter housing. Replacing it promptly avoids more costly repairs down the line.

5. **Compatibility with Modern Diagnostics** OEM parts are programmed or designed to work seamlessly with the vehicle s onboard diagnostics (OBD) system, reducing the risk of error codes or warning lights related to the PCV system.

6. **Warranty Coverage** If the vehicle is still under warranty, using an OEM part may help maintain coverage for related components, depending on the manufacturer s policies.

7. **Long-Term Cost Savings** While the upfront cost of an OEM part may be higher than aftermarket options, it can save money in the long run by avoiding repeated failures or secondary damage to other engine components.

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### **Cons of purchasing a 139-078-34-00 Engine Crankcase Vent Valve**

1. **Higher Cost** OEM parts are typically more expensive than aftermarket alternatives. The price can range significantly depending on the vehicle s age, market demand, and whether the part is new or used. For some owners, this may be a deterrent, especially if the vehicle is older or has lower resale value.

2. **Limited Availability** OEM parts may not always be readily available, particularly for older vehicle models or discontinued parts. This can lead to delays in purchasing or the need to source from specialized suppliers, which may charge premium prices.

3. **Potential for Counterfeit Parts** Even when purchasing from what appears to be a reputable source, there is a risk of receiving a counterfeit OEM part. Counterfeit parts may fail prematurely or not function as intended, leading to further issues.

4. **Overkill for Older Vehicles** If the vehicle is very old (e.g., 20 years) and no longer requires strict emissions compliance, some owners may argue that an aftermarket PCV valve is sufficient. However, this is not recommended, as the valve s failure could still cause engine damage or performance issues.

5. **Installation Complexity** While the PCV valve itself is relatively simple to replace, some vehicles may require additional steps (e.g., clearing error codes, recalibrating the engine control unit, or checking for related leaks). Inexperienced DIYers might find the process more challenging than anticipated.

6. **Environmental and Ethical Concerns** Purchasing OEM parts contributes to the demand for new manufacturing, which may have environmental implications. Some buyers may prefer to support recycling or refurbished parts to reduce waste.

7. **No Performance Advantage** Unlike some aftermarket parts (e.g., high-flow air filters or exhaust systems), the PCV valve does not offer any performance benefits. Its sole purpose is functional maintaining emissions and engine integrity. Thus, the decision to buy it is primarily about reliability and compliance.

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### **Conclusion**

The **Mercedes-Benz 139-078-34-00 Engine Crankcase Vent Valve** is a critical and high-quality component that ensures proper engine function and emissions compliance. While it comes with a higher price tag and potential availability challenges, its reliability, direct compatibility, and long-term benefits outweigh the drawbacks for most owners. The cons are largely mitigated by the part s necessity and the risks associated with neglecting its replacement.

For vehicles where emissions compliance is a priority (e.g., newer models or those subject to regular inspections), the OEM part is the best choice. For older vehicles where emissions regulations are less stringent, an aftermarket part *might* be considered but only if the vehicle s condition and usage justify the risk. However, given the potential for engine damage and secondary issues, even older vehicles benefit from an OEM or high-quality aftermarket PCV valve.

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### **Recommendation**

1. **Prioritize OEM for Critical Applications** If the vehicle is under warranty, requires emissions compliance, or is a high-value model, **purchase the OEM 139-078-34-00 valve** from a trusted supplier (e.g., official Mercedes-Benz dealership, authorized parts distributors, or reputable online retailers like RockAuto, Amazon, or eBay with seller verification). Avoid untested third-party sellers to prevent counterfeit parts.

2. **Verify Part Compatibility** Double-check that this specific part number matches your vehicle s engine and model year. Some Mercedes engines (e.g., M276, M272) may share similar PCV valves, but cross-referencing with your vehicle s service manual or VIN is essential.

3. **Consider Aftermarket as a Last Resort** If the OEM part is unavailable or prohibitively expensive, opt for a **high-quality aftermarket PCV valve** from brands like **Bosch, Mahle, or NGK**, which are known for reliability. Avoid no-name brands that lack proper testing or warranties.

4. **Replace Alongside Related Maintenance** If the PCV valve is part of a larger service (e.g., valve cover gasket replacement, oil change, or emissions inspection), take the opportunity to address any related issues (e.g., leaks, worn seals) to prevent future problems.

5. **Follow Proper Installation Steps** Replace the valve according to the manufacturer s guidelines, including clearing any stored error codes and ensuring the valve is securely installed. Improper installation can lead to leaks or failure.

6. **Monitor Post-Installation Performance** After replacement, observe the vehicle for any unusual noises, warning lights, or performance issues. If problems persist, consult a mechanic to diagnose whether the issue stems from the PCV valve or another component.

**Final Verdict**: For most Mercedes-Benz owners, the **139-078-34-00 OEM PCV valve is the best choice** due to its reliability, emissions compliance, and long-term protection of the engine. The upfront cost is justified by the avoidance of costly repairs and potential emissions failures. Only consider aftermarket alternatives if OEM parts are genuinely unavailable or if the vehicle s age and usage make emissions compliance less critical.

Details:

C63 mags e performance. Electrical parts are not returnable. Genuine Mercedes-Benz Engine Crankcase Vent Valve 139-078-34-00: Parts: Oil Separator. Shipping Carrier substitutions may be made at our determination in an attempt to reduce shipping cost the customer.

Parts must be resalable and in the original packaging.

part #: 1390783400 prices

• $35.75-$520.00

specifications emissyste:

• for makes: Mercedes
• for years: 2023-2025
• mpn: 139-078-34-00
• model: C43 C63 Glc43 Sl43
• part type: Valve Engine Vent
• genuine oem: Yes
• manufacturer warranty: 1 Year
• universal fitment: Direct Replacement
• make: Mercedes-benz
• year: 2023 2024 2025
• parts included: Only Part Reference 0 On The Diagram Is Included
• replaces part number: 1390782800

shipping emissyste:

• service: FedEx Ground / FedEx Home Delivery
• class: Standard
• transit: 5-11 Days
• cost: $25.85
• type: Fixed
• carrier: FedEx

seller emissyste:

• # reviews: 189
• rating: 98.5%
• city: Laguna Niguel, California

returns emissyste:

• time: 30 Days
• policy: Returns Accepted
• paid by: Seller

general emissyste:

• Car Truck Parts Accessories > Exhaust Emission Systems > Other Exhaust Emission Parts
• condition: New

payments emissyste:

• credit card: Visa
• other
• wallet: Google-pay

offer emissyste:

• sold: 0
• availability: In Stock
• quantity: 2
• options: Ship-to-home
• started: April 25, 2026

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