I’m having the same issue with a 2017 550. It’s in the shop now awaiting a new head gasket (that’s somewhere in neverland) according to shipping info. Also a new water pump is to be installed. Mechanics have repeatedly bled the system but after a few hours it overheats. It has something to do with blow back. Once it begins to overheat, the radiator and overfill jug is filled to the brim. One mechanic opened the radiator cap and was drenched in the pressurized fluid! The saga will continue if I ever see the head gasket.
