For about 6 months now I’ve been experiencing a BMW X3 muffler rattle. At first I ignored it but as it became more persistent and embarrassing, I decided to get under the car and troubleshoot it. All the connections under the car were firm and in good condition. What was causing the muffler rattle that sort of sounded like an aluminum can in my exhaust? I also noted, it only seemed to happen on start up, idle, and when the car was under no load decelerating.
I took a video and pasted it below with more details. Basically, there is a baffle in the right exhaust pipe that opens and closes based on a vacuum line. At idle and no load, the baffle closes and it opens once the engine starts winding up. It’s also closed when the car is off. I tried using some penetrating lubrication on it a few times and it’s much better – in the video it still makes a bit of noise but is nearly gone. This morning I didn’t hear anything but if it comes back I might try clamping or disconnecting the vacuum line next. I read about a golf tee mod people to do block the vacuum line completely. My car is a 2008 and has 90K miles on it, if you’re also experiencing this problem or have a comment, feel free to mention it below.
Update:
The rattle is back and worse than ever. I’m going to clamp the vacuum line next, stay tuned for more details on how that goes…
And now the real fix to the Muffler Rattle:
I ended up disconnecting the vacuum actuator which solved the problem permanently. See the top video for this solution, see the bottom video if you want to see the baffle close and hear the rattle it makes.
