rach1507ec

I have a 2013 Edge sport. Recently i have been noticing a rattling noise when i coast/brake, it seems to be on the front passenger side. the rattling started when i coast or brake to 30 mph & stops when i hit 25 mph, now it starts when i'm coasting/braking at 40 mph, still stopping once i reach 25 mph. Can anyone shed some insight on what could be causing this? Thanks so much in advance!!