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      01-14-2012, 01:00 PM   #1
Canefan
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Strange exhaust rattle on startup

I've had my 2008 135i for a couple of months now and one thing that it has done from day 1 is that on each startup I hear I hear a raspy tinny sounding rattle from the exhaust for about 1 second. There is no further sound once the engine is running or when I rev the engine. I also hear it very briefly on shutdown. I assume it's a valve opening (or closing) in the exhaust. Is this normal or is it anything that I should worry about?

Edit: Here's a clip I just made



Anyone elses do this?

Last edited by Canefan; 01-14-2012 at 01:36 PM. Reason: added sound clip
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      01-14-2012, 01:05 PM   #2
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Sounds like one of the CAT's are starting to rattle. Do you hear that sound when going WOT? Keep an eye out, or go see the dealership, they will replace under the emission warranty.
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      01-14-2012, 02:12 PM   #3
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Quote:
Originally Posted by Canefan View Post
Anyone elses do this?

It is hard to hear what that noise is. Make another video starting the car and off and on a few times. So we can hear the sound. I only heard the suspension springs squeaking when you sat in the car. There was a loud-er clicking noise.. but it is too hard to hear in the video.

IF I had to guess I'd say its the flapper valve on the 2nd exhaust pipe. You could clamp(pinch with a rag and vise-grips) the vacum line shut and start the car. The vacum hose is just under the exhaist tips (outer pipe - LEFT).
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      01-14-2012, 02:24 PM   #4
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Quote:
Originally Posted by Dackelone View Post
It is hard to hear what that noise is. Make another video starting the car and off and on a few times. So we can hear the sound. I only heard the suspension springs squeaking when you sat in the car. There was a loud-er clicking noise.. but it is too hard to hear in the video.

IF I had to guess I'd say its the flapper valve on the 2nd exhaust pipe. You could clamp(pinch with a rag and vise-grips) the vacum line shut and start the car. The vacum hose is just under the exhaist tips (outer pipe - LEFT).
Ok - so crimping that vacuum line eliminated the sound entirely. Does that mean that it is entirely benign or do I need to have it taken care of?
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      01-14-2012, 02:39 PM   #5
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Originally Posted by Canefan View Post
Ok - so crimping that vacuum line eliminated the sound entirely. Does that mean that it is entirely benign or do I need to have it taken care of?

It means something is wrong with either the exhaust/actuator. You probably need a new muffler. I say muffler bc the metal valve flap is inside the muffler. The vacuum actuator is just the part that moves the metal exhaust valve. Take it to a dealer and see what they say. Tell them you tested it by crimping off the vacuum line. Sure bet they will fix it.
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      01-14-2012, 03:09 PM   #6
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So I've done a little more reading and it seems that crimping that line is the so-called "golf tee" mod. I went ahead and just zip-tied it as others have done and now that annoying startup sound is gone. I don't really notice much of a difference in exhaust sound. I'll probably remove the zip tie on my next visit to the dealer and have them just fix it.
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      01-29-2013, 12:43 AM   #7
dub shih
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did anyone get this resolved other than doing the golf tee mod?
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      01-29-2013, 09:30 AM   #8
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It's just your exhaust flapper opening on startup and closing on shut down. May be a tad noisier than others cars but you can hear it on any of em if you listen hard enough. Before I got jb4 and set it to be open all the time I could always pick out the sound of it clanking shut on startup and my car only has 1500 miles. I don't think you need to worry.
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      01-29-2013, 05:53 PM   #9
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Gotcha, thank you for the reply.
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      01-29-2013, 07:07 PM   #10
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the first click i heard can be solved by the golf tee mod. Try unplugging the module in the trunk (search for the golf tee mod) and try starting it again. If that solves the issue then maybe that device needs to be replaced.

Nevermind, i am obviously a day late and a dollar short AGAIN///M
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