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🟢 SOLVED: Mercedes W204 C220 CDI oil cooler seal failure — coolant mixing — Mercedes-Benz C-Class 2010 | MyCarFault
🟢 SOLVED 0% 76 fixes reported · 114 driver confirmations

🟢 Mercedes W204 C220 CDI oil cooler seal failure — coolant mixing

Mercedes-Benz C-Class 2010
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⚡ Quick Summary
Severity Level
Critical
Safe to Drive?
🚫 Do NOT Drive
Safety Impact
Direct safety risk — affects safe operation of the vehicle
Urgency Level
🔴 Fix Immediately

Mayonnaise-like emulsion on the oil filler cap and dipstick. Coolant level dropping slowly. The oil cooler mounted on the side of the OM651 engine block uses rubber O-ring seals that harden and fail. This allows engine coolant to mix with engine oil. If caught early, replacing the oil cooler seals and flushing the cooling and lubrication systems is sufficient. If ignored, bearing damage and head gasket failure can result.

Repair / Solution

No confirmed fixes yet. Share yours below.

⚠️ Wrong Diagnosis?

No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this Mercedes-Benz C-Class 2010 problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.

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