The sound only happens when I am backing up and use the brakes, most often when backing out of my driveway on a slight incline. Sounds like a air pump...

I never hear it under other circumstances like moving forward on the same incline.

Thoughts?

 

Hmmm...since no one answered, maybe I failed to explain.

The sound only occurs when backing up with the brakes applied. When I realease the brake petal the sound (The pump like sounds) stops.

Could this be a brake booster problem?

Thanks

 

That is a very uncommon sound and to only have it when you back up is even more perplexing.

You could try disconnecting the vacuum line to the booster and plugging it, then see if the sound is still there to narrow it down.

 

What kind of sound is it?