noise when backing up

before i realized it only made the noise when i put my brake on while backing up i asked a machanic what might cause the noise he said engine mounts.... but i didnt realize it only makes that noise once i apply the brakes in reverse

you didn't describe the noise. could be a worn/loose suspension component noise or some thing with your brake shoes.my own van makes a slight clunk noise in reverse when i hit brakes but so far i just ignore it.