Unknown noise
 

Hi!
I just bought a 2003 Mini from my friend's parents on Feb 16th and am hearing a really strange noise from underneath the hood. If you are standing in front of the car, the noise is coming from the righthand side and sounds like a grinding noise... or maybe like air being force through something. We noticed it on the drive from Oklahoma back to Washington, DC. It didn't do it the morning we left OK, but the morning we left Missouri it was below freezing and from inside the car it sounded like the car was driving over ice or there was ice under the hood. It's a weird grinding noise or loud gurgling that diminishes as the car warms up. I think it eventually goes away, but maybe I just can't hear it over the normal road noise. Any ideas?
I was really hoping to enjoy my new car, and now I'm just concerned. They found a leak in the water pump and replace it (under warranty) and I was hoping that would solve the issue, but it didn't.

Thanks!