vtec99ej

i drive a 99 civic ex, a few weeks back while going through a scp, i was pressing in the brake, and an loud rumbling and vibrating, motion, came from the right side of my car, a few weeks later while in a drive thru, it happend, again, wasnt sure if this was the exhaust, i dont believe it is, then it stopped for a few weeks did it the other day while pressing in the brake again, my maintenced required button has finally turned yellow(not the check engine light) if anyone knows what this could be please let me know, i am very concerned, thanks.