I'm a relatively new 1 series owner. My cars a 2008 135i. Ever since I purchased it, it's had this thumping, popping, creaking sound whenever I would hit humps or dips at an angle. Only at an angle... straight on it wouldn't do it. I thought it might be a subframe bolt or something because it made the noise when the cars body would flex going into dips and stuff. Anyways, the sound seemed to be coming from somewhere in or under my dash. I was pretty certain it wasn't anything suspension related. After looking ALL OVER for anything loose underneath I checked the the brace that runs in a V in the engine bay... sure enough... these bad boys were loose. I gave them a good tightening and hopped in to test. Sound gone. WHEW! So anyways, if you have similar symptoms... perhaps it's these bolts. Sorry, I have no idea what these bolts are called or attached to... some sort of brace. (I'm a car n00b). Picture below shows the ones I tightened.
