SNOWMOBILE QUESTION!?

I have a 1990 Arctic Cat Jag AFS. Awesome Sled :) when i take it out; i can hear a faint clanking type noise coming from inside the hood. Any ideas what this is. It doesn't bother the sleds performance at all. Sled runs GREAT. Today when i took it out tho. I went to apply the brake, and noticed that it was barely stopping. But i was able to stop barely! I took the sled home and opened the hood and it looks like the brake disc is shot. It looks like when i apply the brake; its barely touching and when it does touch, it just scs the metal. So i believe that the disc brake needs replacing. I'm not sure if there is brake fluid on that sled or not that i need to check. Any answers are welcome. Thanks in advance.