Andrew, what lock nuts are you referring to?
Does the bolt NOT go into a threaded hole?
It is secure by a nut on the other side?

Is this not the opening in question?
https://uploads.tapatalk-cdn.com/201...4809f57ad3.jpg


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On e83 I think BMW switched to a threaded insert. E53 uses a nut topside. The nut is a squashed lock nut (compressed a bit to make an oval out of the round hole). You can't thread by hand.


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The access hatch is to allow ring spanner access to the right front nut that holds the plate. The othe five nuts are accessible from the outside but the right engine mount location requires that this nut is accessed from inside and hence the hatch.

My diesel has a second hatch, for access to engine drain bolt.

Slightly different location on X3, but good point by wpoll.
Next time I'm under the car, I will examine access to the bolt nuts on the top side.

On the 3.0 I use a shallow socket to hold the top and impact to spin the bolt


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Doesn't matter what tool you use, you still need this hatch to reached the front right nut. On the diesel, anyway. No way to reach it any other way...

*edit* here's the plate on the diesel...

https://i.ebayimg.com/images/g/18oAA...xAD/s-l300.jpg

Seems the same part number is shared across all 3.0d, 3.0i and 4,4i models, so I'm assuming they are the same. The 4.6iS and 4.8iS seem to have a different part.

I guess I'm still confused. If you're talking about the aluminum stiffening plate under the oil pan, it takes one or two of the acoustic covers depending on model I mentioned above pn 51718268897, ~$12 ea

https://uploads.tapatalk-cdn.com/201...4809f57ad3.jpg

https://i.ebayimg.com/images/g/18oAA...xAD/s-l300.jpg

https://pics.meshok.net/pics2/89548718.jpg

trap door on the underbelly stiffener plate ?
 

Agreed, what exactly was your question OP? The opening I circled in red is 100% the opening to drain the engine oil.



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And it's 100% NOT the oil drain on mine - oil drain is the rear hatch and the front one is for access to the plate securing nut.

It depends on which engine you have... :thumbup: