PCV Oil Separator Diaphragm – Mercedes M278 V8 4.0L 4.6L M157 | OEM 2780100431
The PCV oil separator diaphragm on Mercedes M278 (4.0L, 4.6L V8) and M157 (5.5L, 6.0L V8) engines degrades and causes oil blow-by into the intake, elevated oil consumption, and blue exhaust smoke. OEM P/N 2780100431 is the correct diaphragm membrane for rebuilding the separator instead of replacing the full assembly. Mercedes M278 and M157 PCV oil separator diaphragm (OEM 2780100431) is the primary wear component inside the crankcase ventilation separator on these large V8 engines.
Fits OEM #2780100431.
When to Inspect This Part
- whistling or excessive crankcase vacuum
- rough or unstable idle
- increased oil consumption
- oil residue in the intake
- smoke after warm-up
- mixture faults or an intake air leak
What's Included
- 1× PCV oil separator diaphragm membrane (OEM 2780100431)
OEM Part Numbers and Vehicle Fitment
Additional confirmed fitment
- Mercedes-Benz Mercedes Benz ML-class / GLE (w166)
- Mercedes-Benz Mercedes Benz GL-class / GLS (x166)
- Mercedes-Benz Mercedes Benz SLK/SLC (r172)
- Mercedes-Benz Mercedes Benz E-class (c207, a207)
- Mercedes-Benz Mercedes Benz E-class (w212, v212)
- Mercedes-Benz Mercedes Benz E-class (s212)
- Mercedes-Benz Mercedes Benz CL-class (c216)
- Mercedes-Benz Mercedes Benz CLS-class (c218, x218)
- Mercedes-Benz Mercedes Benz S-class (w221, v221)
- Mercedes-Benz Mercedes Benz SL-Class (r231)
- Mercedes-Benz Mercedes Benz G-class (w463)
- Mercedes-Benz Mercedes Benz S-class Coupe (c217)
- Mercedes-Benz Mercedes Benz S-class (w222, v222, x222)
- Mercedes-Benz Mercedes Benz GLE Coupe (c292)
Part Number / PN
2780100431, A2780100431
Important Fitment Check
Before ordering, compare the part design, dimensions, connectors, and every available OEM/P/N marking with the part installed on the vehicle. Matching OEM/P/N 2780100431 is the primary fitment check.
FAQ
How do I confirm fitment for this PCV Oil Separator Diaphragm?
Compare the exact OEM/P/N and physical design with the installed part. The primary reference is 2780100431. Do not select the part by vehicle model alone.
What symptoms may indicate a problem with this PCV Oil Separator Diaphragm?
Confirmed symptoms include whistling or excessive crankcase vacuum, rough or unstable idle, increased oil consumption, oil residue in the intake. Diagnose the original assembly before ordering so another fault is not mistaken for this part.
What is included with this PCV Oil Separator Diaphragm?
The confirmed kit contents are: 1× PCV oil separator diaphragm membrane (OEM 2780100431).
Does this listing include the complete surrounding assembly?
No. It includes only the item or repair components identified for this SKU. Inspect related parts separately and replace them only when diagnosis confirms a fault.
What should be checked before installation?
Check the OEM/P/N, dimensions, connectors, orientation, and condition of the mating components. Installation should follow the correct service procedure for the specific vehicle and assembly.
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Orders ship within 1–2 business days.
Standard delivery:
- USA: Some items ship from our US warehouse and arrive within 3 business days.
- USA-EU: 10–21 business days
- Worldwide: 14–30 business days
Shipping cost is shown at checkout.
Can I exchange or return an item?
Yes, you can exchange or return an item within 14 days of purchase. This right is guaranteed to you by the Law on the Protection of Consumer Rights
To use this feature, please make sure that:
- the product was not in use and has no traces of use: scratches, chips, abrasions, etc.
- the goods are fully completed and the integrity of the packaging is not violated
- retained all labels and factory markings