Is it stitching OK? I have a Pfaff 18x8 and it is a loud machine. If mine is louder than normal, it is usually stitching badly on the back. If not, I still rethread the top and the bobbin and clean the bobbin very well. Sometimes this helps. Once mine made a terrible noise and I discovered that I had not lowered the foot...lol. I thought I had broke it. Hopefully, it is something simple. Good luck