trap door on the underbelly stiffener plate ?
 

Does X5 have this?

On my X3, the easiest way is to use a screwdriver to pry the tab.
The question becomes, what is the point of this inspection window?

All you can see is that electrical plug (oil level sensor?)
and ground cable

Yes it is present and the only way to drain the oil without completely removing the plate and technically needing to replace all the hardware at a cost of over $100.

It is technically a sound insulation cover to keep engine noise down. They're inexpensive if you have to replace them, pn 51718268897

No, I am talking about the rectangle opening on the METAL plate.
Not the plastic belly pan in front.
There is a different opening for the oil drain bolt.
This is different.

It's just for inspecting and access for some repairs so you don't have to remove the plate.

When installed the bolts are stretched and are constituted single use. I did a test where I followed the torque directions, they break after about 4 Applications and become weak after two.

Most DIY users think of the plate as mere under belly protection but it has a far more important job, it keeps the cat from turning into a parallelogram when there is offset load (example: minor accident bumping something on one side of bumper).

The form on top of the stiffening plate is what absorbs the engine noise

I plan to replace my bolts with 1/2" so I can achieve the same clamping force with a reusable bolt.

Excellent info. But, which repairs exactly? I can't see much inside the hole.
X5 does have the same thing, right? When you get new bolts, please post the specs.

You sacrificed 4 bolts ($60) to test how long they'd last?
I love people like you.

I had to remove the plate for a repair so I did destructive testing on the old bolts that I replaced. You can buy regular M10 bolts for about $3 @ the only thing special about them is a captive washer. You don't need to spend $20@. Also the nuts are special squashed lock nuts and should also not be reused.

I decided I'd rather not replace the bolts so I figured out the clamping force of the factory design (about 9-10,000#) and determined that is much less than standard torque of either 12.8 M10 (just upgrade the bolt) or a bigger bolt M12 or 1/2" SAE. Then you can torque them to normal design as many times as you want and achieve the design clamping force.

The one repair I used the window for was replacing the CV axle. Was glad I had the hole so I didn't have to remove the plate

[emoji848]
Andrew if I'd have known you were getting the stiffening plate bolt discussion started in time for Christmas I would have gotten everyone else something too..[emoji1787][emoji1787]

Best. Christmas. Ever...!![emoji56]
[emoji897]

Merry Christmas in the land of the big PX from the land of no PX

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