There's an o-ring in there and it will be 'snug' to 'really snug' depending on the skill of the guy who tightened it last.

Lefty - loosey, even when you are on your back...

Not sure that the torque value should be as I don't have the Bentley manual handy.

4" allen wrench is tough to turn by hand. Get a set of allen head sockets instead. 3/8 drive ratchet and I bet it doesn't feel all the snug.

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual