I was out for a test drive this evening and when I came home and pulled into my parking spot, I put on the parking break, and with the engine still idling but the transmission in neutral, I noticed that there was a rattling occurring in sync with the speed of the engine idling. It sounded sort of like a distant jackhammer. When I pushed in the clutch and let it out, it went away. Then it came back, I think after I pressed the clutch in and let it out again.

I looked under the hood to see if I could hear where it was coming from. It sounded like it was maybe from behind the engine (I guess where the transmission is), but I am not sure.

I noticed it once earlier when I parked on the side of the street, also I think with the parking break on (can't remember for sure). Also went away that time when I pressed in the clutch pedal.

Any ideas where to start?

Something to note: the exhaust is held on in one spot by bent coat hangers rather than the rubber donuts (temp fix until I get new donuts), but I don't notice any rattling with it otherwise.

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