I had the exact same noise, it was the left ball joint.
I got the ball joint from an online benz shop for $52, rigged a coil spring compressor from bolts and a piece of chain, and autozone loaned me a little press, 3 hrs later, new ball joint in place.
Examine the boots around the ball joint closely, perhaps they are cracked in the back or something that has let water in and thus dried them out.
Good Luck.