My 02 LS 3.4 is making a chattering noise. It has made this noise since I bought it three years ago. It had 82,890 miles on it when I bought it and now has 148,320 miles. Last summer it went for a week knocking like crazy but stopped all a sudden when my buddy added a touch of Marvel mystery oil and has not returned. The belt squealed for the better part of 4 months then quit one day on its own. It heals itself lol but the chatter wont go away. The car runs great other than that. It is just annoying sounding because its not a pos. I love my Monte. Is this a serious problem or is it common? How do I fix it?