Don't take that apart if I don't need to. If the o-ring hasn't spilled out yet then I personally would drill a 7/64 hole through and put in a stainless 3mm screw (flat head so the cone of the head will make a tight seal). Unless they changed the design it's inevitable to fail, the part that holds it together is opposite the side that pushes apart it's quite literally designed to fail.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)