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Discussion Starter #1
I noticed a slight rattle from underneath my 04 stang GT this spring, and its become much more pronounced, driving me nuts. My exhaust consists of a BBK O/R x-pipe, and Flowmaster catback, with 10K miles and rust-free. Due to its low height, ive scraped it a couple of times on driveways. I thought it could be the cover to the clutch yoke hitting my O2 sensor, so I modified the cover to increase the clearance. Saved my O2 sensor, but didn't help the rattling.
I noticed the rattling, tinny, sound seems louder when the exhaust is cool. Right after I started the car, I took a 2x4 and applied pressure under my x-pipe, and the rattle stopped. I thought it might just be loose flange bolts, so checked and was able to tighten quite a bit. Started the car, and the rattle is still there.
I was thinking from the exuast bottoming out, it may have pulled the flanges loose, or damaged them, however they appear o.k. Before I start putting to many hours into this deal, do any of you have any suggestions to help kill this rattle?
 

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Have you checked your heat shields? or for any loose u bolts?
 

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Discussion Starter #3
I had a bent heat shield on my old car which made a loud sound, but this mustang doesn't have any that Ive found, also isn't anything resting or touching exhaust. I was just checking it a bit ago, applied pressure near x-pipes flanges, and it goes away, release pressure and the tinny sound comes back. If I replace the flanges, do you know if the exhaust hangers will need to come off, or will the exhaust stay in line close enough to bolt back together easily.
 

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Check the clearances between the rear hangars and the frame of the car. I just payed nearly $100 in shipping to return one of my pypes mufflers that banged itself to death on the rear frame of the car, and to look at it on jack stands, it looked like it had plenty of clearance. Once a butt is in the seat though, the geometry changed, and the hangar started telographing against the rear frame. Never found it until it was too late, and a weld inside the muffler went bad. Pypes are good people tho, and they are replacing it for free, and I will insure proper instal this time (midas did it for me last time, and they clearly did a "bang up" job!) Look for subtle mushrooming on the end of the hangar tip, if you see ANY, then it is probably touching the frame. Might not be your prob, but won't hurt to check.
 

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Midas

Check the clearances between the rear hangars and the frame of the car. I just payed nearly $100 in shipping to return one of my pypes mufflers that banged itself to death on the rear frame of the car, and to look at it on jack stands, it looked like it had plenty of clearance. Once a butt is in the seat though, the geometry changed, and the hangar started telographing against the rear frame. Never found it until it was too late, and a weld inside the muffler went bad. Pypes are good people tho, and they are replacing it for free, and I will insure proper instal this time (midas did it for me last time, and they clearly did a "bang up" job!) Look for subtle mushrooming on the end of the hangar tip, if you see ANY, then it is probably touching the frame. Might not be your prob, but won't hurt to check.
You just said the magik word, "Midas".

I don't do business with those guys. Long story...

And good advice about the noise maker - its good to get on the problem right away when you hear this stuff.

Odds are that something HAS been bent or moved - or a hanger is messed up - and causing the racket. Rather than remove the midpipe completely, I would suggest loosening JUST the suspect hardware first, checking the fit and then re-tightening. Check for the noise. Repeat at every joint if necessary. Even so, you might discover that the entire unit has been slightly bent out of true, and some adjustment with the pipes is needed to regain a comfortable alignment.
 

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Could be the Flows, how old are they?. They have baffles inside that like to rattle around after a while. If you have a rubber mallet get under the car and start tapping around the whole system. If there's something loose you will hear it.
 

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My magnapacks rattled against the underside were a passengers foot would normally be. It took me a few weeks to catch my jacksrands were loaned out but it may be something you want to check into.
 

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Discussion Starter #8
I checked all the clearances again, and can fit my whole hand easily between most places. I think its gotta be a flange or in the exhaust like gnats said. I'll go out and tap around with my rubber mallet.
Do you know if there is anything IN the x-pipe that could come lose besides the unions?
Also, I got a couple full turns out of the flange bolts and could tighten a little more if needed, any idea how tight these should be? Are they usually impacted?
 

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Discussion Starter #9
Finally got time to raise the car and tap around. I first found the washers rattling under an o2 sensor, so I got those tightened down. Still made the sound. Now, I just noticed the Dvr Sd pipe seems to be a little loose where it connects to the exhaust manifold. I tried tightening the 2 bolts, with a breaker bar, and they won't budge, and don't have an impact wrench. I'm worried that the pipe might have worn out around the manifold outlet....:so
 

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I have the same problem i have a x pipe with flowmaster it almost sounds like theres something in the muffler! going to take it to the shop and cut off the muffler and check it out!:bigthumbsup
 
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