I feel like this one is something everyone will benefit from.
I went to the dealer to get a new bleader screw. Mine did not have the o ring and was leaking. P/N 17-11-1-712-788-8
I also picked up this cherry from the service guy. He said that the nipples that typically go out are not in the ETK, and not something many people talk about. He just happend to know about it becuase one of the old time BMW guys was talking about it a while back. Anyway, you can pick up this part that fails most often in the radiator. It is the radiator fitting that goes from the plastic tank to the expansion tank. P/N 99-00-0-003-352. Hard to find BUT can be ordered. I would suggest that everyone go out and spend $3.50 to pick one up. Put it in your glovebox and forget about most of the radiator issues.
This nipple and the expansion tank from what I understand are the two weakest links in the radiator.