[HerkHealer]

Originally Posted by sam555

Thanks to NateM15 and HerkHealer . My cap area was looking very similar. Happy to report that I replaced it and see no tell tale signs for the last two days of any leaking coolant on top. The cap I used was a CarQuest cap from Advance Auto. For whatveer reason it is a much more snug fit than the original. The original cap has this slight bit extra space in front and looks a lot like HerkHealer 's pic. With the CarQuest cap that is not there. Keeping fingers crossed and hope this solves the problem...

The OEM BMW cap I replaced felt more "secure" and firm as I installed it too.
I wonder if BMW used a larger O ring. Seems likely.
I've not had any cap leaks since changing it out as well.
And that's almost 2 years now.