BMW reports on an oil leak that may affect models: all E82, E83, E88, E85, E86, E60, E61, E70, E90, E91, E92 and E93 vehicles with N51, N52 or N52K engines.
An engine oil leak can be seen coming from the right side of the engine crankcase near the coolant port. Removing the coolant pipe shows that the oil leak can be evident from the separation of the two crankcase materials (aluminum and magnesium) or one of the coolant pipe attachment bolt holes.
The cause is a very small leak at the main oil galley between the aluminum and the magnesium portion of the engine crankcase.
Do not attempt to reseal. Resealing may cause engine oil leakage to enter the cooling system, resulting in contamination and further damage to cooling system components. The engine crankcase will need to be replaced.