Oil Consumption on Your Mercedes M278 V8? Replace the Separator Diaphragm for $14.
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.
✓ What You Get: PCV oil separator diaphragm for Mercedes M278 V8 (4.0L/4.6L) and M157 V8 (5.5L/6.0L) — stops oil blow-by and reduces oil consumption.
What's Included
- 1× PCV oil separator diaphragm membrane (OEM 2780100431)
Why Replace?
- Stops Oil Blow-By: Failed membrane allows oil mist into the intake system and intercooler.
- Reduces Oil Consumption: Properly sealed PCV circuit keeps oil in the crankcase.
- Eliminates Blue Smoke: Stops oil burn from ingested crankcase vapors.
- Saves $200+ vs Assembly: OEM separator assembly costs $230+; this membrane alone rebuilds it for $14.
Vehicle Compatibility
| Make | Model | Engine |
|---|---|---|
| Mercedes-Benz | S-Class, CL, SL, GL, GLS | M278 4.0L / 4.6L V8 |
| Mercedes-Benz / AMG | S63, CL63, SL63, ML63 | M157 5.5L / 6.0L V8 |
About This Part
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. Membrane failure is a frequent cause of oil consumption complaints and blue exhaust smoke on S-Class, CL, SL, GL, and AMG models with M278 or M157 powertrains.
⚠ Verify Part Number Before Ordering: Confirm OEM 2780100431 matches your separator assembly before purchasing.
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