When I take hard left turns, pretty much only when turning 90 degrees onto a new street, I hear this "kwuk kwuk kwuk" in the back, kind of like plastic bottles rolling around in the back of my car. If I'm going faster, I tried through an intersection at 40mph or so the other day, and the sound was similar but the pitch of each noise and the frequency at which they occurred was higher (almost like a squeaking at that point). I've driven the car maybe four or five times since it started happening, hoping to get a chance to look underneath the car.
It /seems/ to be coming from the back right wheel, so I rolled that side up onto a wheel ramp (to emulate a left turn) but couldn't see anything that might be making contact with anything else. I took the wheel off, and while there was a spot on the rim that looked like it /could/ be rubbing somewhere (because it wasn't as dirty as the rest of the wheel), but I couldn't find anything that it might be rubbing on. With the car in neutral and the parking brake off, pulling on the wheel didn't indicate to me that anything was loose, and it certainly didn't bind or rub anywhere other than what I was getting from the brake pads.
So my initial thoughts were that maybe I needed to tear apart the wheel bearings and grease them up, although looking at Performance Products' online schematics makes it look like the bearings are possibly all sealed and maintenance-free. So new bearings then? Looking at the CD manual that I have, it looks like more of a job than I want to deal with, not to mention I haven't got any sufficient pullers or any of that jazz. I'd like to avoid the shop though, if I can; there's one local not-dealer Mercedes shop, they seem to do good work, but they don't entirely fill me with confidence.
thx,
-tom!