Originally Posted by josiahg52

I don't know about failing but I guess the o-ring could go bad. I'm much more familiar with the reservoir and system in my 2001 M5. The cap on that reservoir has a vent hole. During the hot summer months and definitely during any type of spirited driving, it would spew fluid all over. First, I made a catch can but finally flushed the system with new synthetic ATF and replaced the reservoir/filter. Used the same cap. No problems for ten years and a lot of miles.