One of the most common causes of front end clunk or noise with Ford strut suspension cars (and extremely common with Windstar,) is simply rocks in the springs! Small pebbles are kicked up by the tires and build on the lower spring base rubber pads. The stabilizer bars are another common problem. They tend to rust from the inside out and break next to or inside the frame mount bushings. Also like any shock, the struts themselves become lose internally and the piston bangs when it changes from compression to extension. Bad tie rods or ball joints are usually accompanied by abnormal tire wear and stability problems.