check your brake pads, there is a spring on them that keeps them from raddling. One broke off of my 90 740 at 130k mi it sounds terrible.

Good advice from Matt. If the car has close to or more than 100k miles on it go through the entire front end if it has not been done already.

Clunking noises are hard to diagnose. Most common causes: front strut rod bushings (where the strut rod meets the control arm), lower ball joints, sway bar bushings. Less likely causes: outer tie rod ends, inner tie rod ends, upper ball joint / upper strut bearing, rear strut rod bushing (where the strut rod bolts to the frame), inner control arm bushing (where the control arm bolts to the frame).

Take a look at the rubber boots on the lower ball joints... if they are split, I'd replace them. While you have the front end disassembled, I'd go ahead and replace the conical front strut rod bushings, sway bar bushings, and outer tie rod ends also. Total cost for parts should be around $100, maybe $150 from your favorite online parts vendor. Labor around 3 or 4 hours (it least that's what it takes me). You'll also need a front-end alignment ($50).