i have a 2011 bmw 3351 series, I keep getting an overheat warning.

What is your question?

my mechanic has replaced all cooling components (radiator, water pump, etc.) that he can think of, but warning continues to come on. normally warning comes on after driving the vehicle for 23 minutes. warning goes off in a few minutes and the vehicle is good for another 23 minutes. becoming and expensive problem. vehicle was kept at bmw agency for two weeks and problem came back on after a year. Have been taking vehicle to a private mechanic.