See attached pic of the S54 oil filler cap that (according to the parts CD) should be on our cars instead of the ones from the pre '01 cars that we got. The one that came with my car and some others I know of leak. I've had the cap from my 318ti on my car for some time now. It has a different base and so far it doesn't leak. The base of the new S54 one is identical to the 318ti one, so I assume that it won't leak either. We'll see. The inner ring on the new style one must be what makes this one work. Put 25 miles on the new one today and so far no leaks.
BMW in their wisdom rotated the ///M filler cap to match the colored one on the valve cover. Instead of rotating the filler cap they rotated the cover where it mounts. This placed the slots in the mount side to side instead of up and down. Being up and down the slots must have let the oil drain back before leaking. I'm assuming this since BMW drilled a hole where the slot used to be, I assume to let the oil drain back. The hole isn't large enough and the cap leaks.
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