Air coming out of euphonium bell?

I recently got a new school owned instrument that looked a little banged up to me when I first saw it. I played on it a little and I noticed I had an exceptionally air-y tone compared to what I had before. I tried using various mouthpieces---all had the same result. I also tried using my friend's euphonium with these same mouth pieces, and my tone was just fine and not air-y. For some odd reason, I decided to put my hand over the bell to see if I could feel any airflow and sure enough there was. There was an abnormal amount of air coming out the bell. To me, it sounds like there could be a small dent or something that is causing the air to escape. Would I be right in saying this? If not, what does this sound like to you? Is it normal? Thanks for your help.