New Catback Exhaust - Rattling Noise

StangLuv

New Member
Jun 5, 2010
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I recently had a Magnaflow Catback Dual Exhaust installed, and when I'm at idle in gear there's a loud rattling noise coming from underneath the car. Whenever I accelerate or move just a little, or put the trans in Neutral, the sound goes away. Sometimes the sound goes away when idle, but if stopped and I turn the wheel left or right the sound is worse, then when wheels are straight again the sound goes away.

Because turning the wheels made the sound come or go randomly this led me to believe that the exhaust was hitting something but I looked underneath and nothing is touching except for the exhaust hangars which are setup correctly. Next guess was a loose heatshield over the cat or mufflers but everything is still.

Just recently a slight drone comes whenever I accelerate.

Any help you can provide is greatly appreciated and I'll try to keep this updated.

UPDATE: This morning after cold start and driving the sound was gone but after short drive the sound returned. So I stepped outside and listened and it's not a sound being produced by the exhaust, it does sound like something on the outside of the exhaust rattling against something. But nothing past the y-pipe is touching the chassis. I will take some underbody pics and attach them.

11/18/2010 - The rattle is from something vibrating against the fuel tank, but when I looked under nothing was touching, I will try to get better pictures.
NEW SYMPTOMS - There was heavy smoke coming from both exhausts after the car was shut off. Also while driving, I could hear a liquid or marble sound coming from the cat converter on the driver side when I hit small bumps. And also the right tailpipe was leaking oil-like liquid

All these symptoms became prominent after installing the catback dual exhaust
 
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When the noise is more consistent I will try and upload a video to YouTube and post the link here, hopefully having visual/sound helps determine the cause of this.

UPDATE: http://www.youtube.com/watch?v=shbKZ7rDXy0
Managed to capture the sound. Sorry I didn't spend too much time trying to get a shot underneath the car, it was dark and the sound wasn't consistent during the daytime.
 
I may have a very good idea as to what it is. I replaced my exhaust a couple of days ago and had a similar noise. The tail pipes are over the axle and they have two hangers. The clearance is 1/2" on one side and less on the other as they go over. If you have one side of the car up and climb underneath the gas tank, the hangers are quite accessible but it took me days to get them to clear just right.
You just got the exhaust system so I would call them and let them know about the noise and the possibility its the tail pipes or some part of the exhaust.
If you can, doing it safely, do it yourself before the possibility the pipes are burning something.
 
Thanks Robbi and yes we found out what was happening! It's just a bolt on kit so starting out there was clearance but after the car shakes when driving (especially with my stiff suspension) it rocks the exhaust pipe thats over the axle and starts to touch the fuel tanks gravel protector. The shop put on a heavier duty clamp to get the job done but if it starts to shift back again i'm going to go ahead and have them weld the piece so it no longer shifts again. Thanks for the advice!