I have noticed an occasional rattling noise when cold from what a thought was a loose heat shield on my new-to-me 940.

Today, when I started the car to come home it sounded like a rotations squeaking but I could not find a cause under the hood. It is RPM specific but not speed related.

I checked the timing cover which has a broken bolt hole...not rubbing.

Checked belt tension...none loose but a couple of collapsed acc bushings as expected.

Still sounded like a rattling heat shield because it came from under the car about firewall or slightly behind. So I got out my ramps. The moment the front wheels cleared the ground...sound is gone. Checked the heat shield on the header...it is gone from rust...not there.

Cat was way too hot to check but I noticed a new cat back, over the the axle pipe made of standard muffler-shop grade tube and bends.

So my two guesses are the Cat heat shield or other exhaust component rattling due to poor alignment on the new exhaust pieces or the harmonic balancer.

Unrelated note, starter had its first hiccup today after what seemed like always being a bit slow. I am guessing a rebuild is in my future. Time to find that elusive small electric motor shop.