The vanos actuator has rubber o-rings that harden and cause the seal to leak. I've done the o-ring replacement on M62 vanos not sure if there is an equivalent fix for M54/ N62 vanos which looks a lot different (but also cost a whole lot less).

When I did the vanos overhaul on M62, new vanos unit was $550@ and it was about $60 for the o-ring kit and $50-80 for the tool to slightly crush the vanos "just right" to tighten up an internal o-ring that you can't access. Genius fix and works well.

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