The F90 M5 with engine S63M is being recalled by BMW to check/replace the coolant expansion tank. The tank is located in the hot V of the engine and is subject to failure along a plastic seam, the end result could be damaged injectors leading to possible engine damage. See below for more information.
Below is an extract from the recall document I found on-line for Service Bulletin 0017220200.
My car is scheduled to have the replacement tank before then end of May.
