Exhaust Rattle
 

http://www.youtube.com/watch?v=0QnkuNQqMfE

My car's been rattling at 30kmph+. Frined told me to get under my car and tap things with a mallet. Video is shot from directly behind the front passenger wheel, underneath the car. I hit the offending piece of metal (a large metal shell) a couple times with the mallet...and then I hit the exhaust pipes to demonstrate the overall noise. Lo and behold that thing around the exhaust system is loose. What is it / what can I do?

Also, the last part of the video shows my jack stands. That's the front cross member right ? Is it a good place to put my stands?

depends where it is. i've had a loose exhaust bracket that i just removed and didn't replace. whether or not that is a big deal i don't know. personally i don't think so. my car have a few exhaust brackets. sometimes they rust through, get loose and rattle. so i just took it off. now it no longer rattles. that was over a year ago now and its fine.

http://realoem.com/bmw/showparts.do?...53&hg=18&fg=10

The part I was tapping wiht my mallet were the pieces of metal on part 1... The sectioned portions immediately to the right of the label 1. They are loose.

^ are they the actual pieces that are rattling against each other? or is there something loose that may be rattling against them?

The actual pieces. They are loose on the tubes.

Those are the shields on the cats.

Is there any easy fix or anything? Any ideas? How are they originally fitted ?

I used an exhaust u-clamp to clam the "nose" of the shield firmly down, haven't had any rattles since (30k + of "spirited" driving through mostly bump roads on rubber band tires).

just rip it off...

http://www.acs-pro.de/resources/Wedge/S0145.jpg
One of those bad boys?

Yup. Cant remember the size though.

i usually re-weld them on if they arent too rotted

By heat shield, you do mean the things actually attached to the piping right? Not the piece in this picture:
http://home.comcast.net/~titansilber/Heatshield-1.JPG

I'm referring to actually circular pieces of metal rattling around the exhaust/cat piping.

Could it be the item circled. I've seen that bolt come loose, and the two pieces rattle at different RPM's/Engine Load.

I believe its the pieces between the label 1 and label 16 - the two ribbed circular pieces on the main tube. They are loose.