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Old 09-13-2012, 01:58 PM   #1
doww301
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Hole drilled in mid pipe exhaust sleeve

Hi Folks: Got a question. I have an '06 a4 goat; and, on this car, I have a 3/8" round hole drilled in the tope of the sleeve where the mid pipe flange is welded. The sleeve is toward the cat on the passenger side mid pipe. This hole shoots exhaust directly up on the heat shield attached to the bottom of the car. Also, it affects the sound of the car. I only noticed this sound difference recently so my question is, is there supposed to be some device or bolt that normally fits into this hole and blocks the exhaust? If so, this makes no sense to me. I can't think of any normal reason why this hole should be there. I did a pretty exhaustive search and couldn't find anything on it which only reinforces my opinion on this. Here is a photo of the sleeve-I think it's a factory installed item. Sorry I couldn't get a photo of the hole but it's right on the top of that sleeve the flange bolts to. Any Ideas other than something dumb that somebody did before I owned the car, or is this a factory screw up that I only recently noticed? Thanks in advance for help on this!
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Old 09-13-2012, 06:12 PM   #2
littlecrunch2000
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If it was bigger, I would have guess the O2 sensor, but it's not that. Could it be an exhaust leak that has grown bigger? I know most exhaust leak holes that get bigger tend to look like a perfect circle.... I'm thinking physics here with circles being the most efficent shape for air and energy...
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Old 09-15-2012, 01:46 AM   #3
doww301
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No, it's actually a hole

I found out that it's where a bolt was inserted into the sleeve to which the flange is welded. Why? No idea. A tech at the local GM dealer verified that this is in fact a bolt hole where a 10mm bolt was inserted at the factory. He didn't know why they did that either. Anyway, I'm gonna get a replacement bolt and loctite it in place and hope fully be done with this.
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