Hey guys, I'm posting on behalf of my dad. He has an 08 6.4 with about 57,000 miles on it. Just a couple days ago it started to make a strange rattling noise under the hood. From what I can tell, it seems to be coming from the passenger side, nearer to the front. It sounds almost like a constant buzzing, and will do it even at idle. You can't hear it inside the cab so I don't know if it quits when driving. I'm thinking there is just something loose, but I'm no expert. If anybody has any idea what this might be, I'd appreciate it