Had to replace expansion tank after 2 months
I did the cooling system refresh this summer (in Texas) on my 2002 540 M Sport and used a Behr expansion tank from OEMbimmerparts. It lasted 2months and started leaking. I replaced it with a BMW expansion tank last night and OEMbimmerparts has given me a RMO to refund my money.
Believe it when everyone says to stick with the BMW expansion tank (through experience).