lol...trick question? it's an e53 (3.0 2002 x5). the reason i took the cover off was (i thought) to change the "lower radiator hose," which the dealer wanted some ridiculou$ amount for; seemed straightforward enough to give it a shot.

i earlier got a low coolant level message and ssaw the temp rising. cut the car off, added distilled water. next a.m. seemed distilled water was on garage floor. haven't driven it while i ordered the coolant, and the hose, and the oring (and the floor jack, and the jack stands :)) welp, hm. erg. i was expecting a dangling hose. heater doesn't seem to be working btw. related symptom? but not exactly sure as i haven't run the machine long enough to tell if it just needed "warmed up."

Could it be remains of a dust cap from one on the serpentine belt pulleys? Can you see if any of them are missing?

Knowing that you have a 3.0i (aka M54B30) engine helps. The engines have different physical layouts, obviously, but more importantly, we all have different experiences with our E53's and where I may be able to help with your M54, I wouldn't be much help with an N62...

You did the best thing shutting her off when you saw the temp climb. These M54's HATE high temps... quickest way to a blown head gasket, or worse...

The belt pulley dust caps aren't flat like that. Almost looks like some kind of silicone sealer around the circumference of that plastic as well.

could this be where it fell from? looks like some of the same material (silicone?) and the same basic size/shape. and.......what is this area/part called?

That appears to be the fan shroud. Wracking my brain for what that circular feature is though... I've had my shroud off for a couple years, and I don't remember any such feature on mine. :dunno:

The dust cap guess was definitely a long shot. I just can't think of anything else in the general area that is round, plastic, and about that size. It looks like it either has a bunch of black sealant goop around the edge, or melted plastic - hard to tell from the photos.

What angle was this last photo taken from? Is it looking up from underneath?

yep last photo was from underneath.

I had my fan shroud out last week, and it doesn't have a round feature like that. The photo is taken at an odd angle and it's a little disorienting!

seems strange for a circular piece of plastic to be silicone'd to a bmw .......just get some silicone and slap it back up there? no way?! i just can't tell if this is a serious problem or??? maybe i'll pour some more distilled water into coolant tank and see if it comes out of semi triangular component.