Less than a week ago I bought a 2002 Subaru impreza outback sport. Fun little car. However two days after I bought it I started to notice a noise coming from the back passenger side of the car. It sounds sort of like scrapping a plastic fork against metal. I have looked everywhere for anything that could be making the noise, as it seems to be coming from inside the car. IT also seems to get worse the longer I drive. I commute to work, and so for the first 10 minutes it’s silent, then gets louder and louder, by the time I get to work its noticeably loud. Any thoughts?
I’d inspect the heat shields around your muffler. There are some where they come out of your engine but those may be fine. They’re are some more on your catalytic converter that are kind of located in the area your mentioned. Their mounting points often rot off and it starts resonating. If that is the case, you could put a large band clamp around it. That very often kills the resonance.
Maybe rock stuck in your brake rotor shield? However it would be somewhat in time with the rotation of wheels and stop when you stop.