BMW 730d Oil Cooler Matrix Failure — Coolant Contamination
The oil cooler matrix on M57 engines cracks internally, allowing coolant and oil to mix. Chocolate milkshake in the coolant reservoir and frothy oil on the dipstick are the definitive signs. This requires immediate repair — continued operation causes bearing failure within a short distance. The oil cooler is integrated with the filter housing on M57.
Repair / Solution
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