Heat Shield rattle....may need tech help
1st Gear
Joined: May 2007
Posts: 167
From: MICHIGAN
RE: Heat Shield rattle....may need tech help
I thought it was my cat, but the shop told me that if it was the cat you should be able to hear it by simply banging on it,(engine off). Thusly, it was determined that it was the inner pipe. beng
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1st Gear
Joined: Jun 2007
Posts: 91
From: Fort Wayne, IN
Hey guys, im back with an update:
I took the car in to finnaly get this thing fixed and it was officially the heat shield.
Evidently there was a crack where the heat shield bolts only the undercarriage which (after running for a bit) would loosen up and start a shakin'. SO, I have a new heat shield on the way and will have it replaced within the next week or so.
The dealer did suggest that I could probably take it to an exhaust shop and they may be able to weld it up and remove the noise. BUT, seeing as most shops around here employ people who like nascar and dont know the first thing about german cars, I thought id pay the extra coin and have the dealer just get me a new one.
Hope this helps, ill update again after its replaced and confirm the fix.
I took the car in to finnaly get this thing fixed and it was officially the heat shield.
Evidently there was a crack where the heat shield bolts only the undercarriage which (after running for a bit) would loosen up and start a shakin'. SO, I have a new heat shield on the way and will have it replaced within the next week or so.
The dealer did suggest that I could probably take it to an exhaust shop and they may be able to weld it up and remove the noise. BUT, seeing as most shops around here employ people who like nascar and dont know the first thing about german cars, I thought id pay the extra coin and have the dealer just get me a new one.
Hope this helps, ill update again after its replaced and confirm the fix.
1st Gear
Joined: May 2010
Posts: 5
Hi,
I realise the age of this thread
but for anybody who originally posted on it (or anybody elkse of course), did the noise sound anything like this?...
http://www.youtube.com/watch?v=6CUMpEQp5-w
I already have a seperate thread on my issue but for what its worth, with any luck and all that
I realise the age of this thread
but for anybody who originally posted on it (or anybody elkse of course), did the noise sound anything like this?...http://www.youtube.com/watch?v=6CUMpEQp5-w
I already have a seperate thread on my issue but for what its worth, with any luck and all that
1st Gear
Joined: Sep 2008
Posts: 125
From: Grand Haven, MI
I had a very similar problem with my wife's A6. Here's a quick list of the things I tried that didn't work:
I did some research and read that Audi used special "double-wall" exhaust tubing that could come loose and rattle on the inside, making it hard to identify the source. Aha! Simple. All I had to do was remove each front pipe and cat and see if they rattled when I hit them with a hammer. It turned out to be a bit of a challenge to remove the manifold bolts, but I got each pipe off (except for the O2 sensors, so they were still attached by the wire harness), but there was no sign of double-wall anything, and I couldn't make them rattle with any hammer I owned. Back to the drawing board.
My wife was already annoyed, but I assured her that I was close to figuring it out, and I got back to work. My next attempt involved cutting the bottom of each cat open to see if the catalyst had broken loose inside. I found out that they're surprisingly difficult to cut through! Must be the German steel. The passenger side cat had several loose pieces of catalyst inside. Jackpot! I removed them and had my brother weld it closed again. As a formality, I cut the driver side cat open, and to my surprise it was completely empty. Weird. There was an O2 sensor right behind the cat, so the catalyst would have to have broken up into tiny pieces to get blown further down the pipe, and that seemed unlikely. My brother welded that one back together while I tried to figure out where the catalyst went, but I decided that I didn't really care as long as it was fixed. Imagine my disappointment when the rattle was just as bad with the empty cats when I put everything back together.
Next I removed the entire exhaust system behind the couplers to see if there were any chunks of catalyst rattling around in the three mufflers. Of course there weren't, so I put it all back together again so my wife could continue enjoying the obnoxious rattle.
I decided to see what it would cost to buy new pipe and cat assemblies. Based on the dealer prices, it would have been less expensive to buy another A6 than to replace the cats, which was no good. Instead, I bought two universal cats (about $60 each) to replace the stockers. It wasn't easy to cut the old ones off, but when I did, I found an important clue. Someone at Audi thought it would be a good idea to add an extra triangular piece of steel in the front of each cat where the pipe diameter expands to the full cross-section width. Although the rest of the car seems to be built like the proverbial brick outhouse, these pieces of metal were apparently only held in place by a couple of spot welds. Once those failed, they turned into some kind of super-resonators that rattled crazily at most engine RPM's but were strangely silent during any manner of troubleshooting.
The good news is that welding in the universal cats took care of the rattle, my wife was happier with the car (and with me), and I was free to investigate the mysterious rattle that was coming from the engine compartment (it turned out to be the serpentine belt tensioner that grenaded on my wife while I was in Mexico on business, but that's another post).
Good luck with the diagnosis. I hope you find it sooner than I did.
I did some research and read that Audi used special "double-wall" exhaust tubing that could come loose and rattle on the inside, making it hard to identify the source. Aha! Simple. All I had to do was remove each front pipe and cat and see if they rattled when I hit them with a hammer. It turned out to be a bit of a challenge to remove the manifold bolts, but I got each pipe off (except for the O2 sensors, so they were still attached by the wire harness), but there was no sign of double-wall anything, and I couldn't make them rattle with any hammer I owned. Back to the drawing board.
My wife was already annoyed, but I assured her that I was close to figuring it out, and I got back to work. My next attempt involved cutting the bottom of each cat open to see if the catalyst had broken loose inside. I found out that they're surprisingly difficult to cut through! Must be the German steel. The passenger side cat had several loose pieces of catalyst inside. Jackpot! I removed them and had my brother weld it closed again. As a formality, I cut the driver side cat open, and to my surprise it was completely empty. Weird. There was an O2 sensor right behind the cat, so the catalyst would have to have broken up into tiny pieces to get blown further down the pipe, and that seemed unlikely. My brother welded that one back together while I tried to figure out where the catalyst went, but I decided that I didn't really care as long as it was fixed. Imagine my disappointment when the rattle was just as bad with the empty cats when I put everything back together.
Next I removed the entire exhaust system behind the couplers to see if there were any chunks of catalyst rattling around in the three mufflers. Of course there weren't, so I put it all back together again so my wife could continue enjoying the obnoxious rattle.
I decided to see what it would cost to buy new pipe and cat assemblies. Based on the dealer prices, it would have been less expensive to buy another A6 than to replace the cats, which was no good. Instead, I bought two universal cats (about $60 each) to replace the stockers. It wasn't easy to cut the old ones off, but when I did, I found an important clue. Someone at Audi thought it would be a good idea to add an extra triangular piece of steel in the front of each cat where the pipe diameter expands to the full cross-section width. Although the rest of the car seems to be built like the proverbial brick outhouse, these pieces of metal were apparently only held in place by a couple of spot welds. Once those failed, they turned into some kind of super-resonators that rattled crazily at most engine RPM's but were strangely silent during any manner of troubleshooting.
The good news is that welding in the universal cats took care of the rattle, my wife was happier with the car (and with me), and I was free to investigate the mysterious rattle that was coming from the engine compartment (it turned out to be the serpentine belt tensioner that grenaded on my wife while I was in Mexico on business, but that's another post).
Good luck with the diagnosis. I hope you find it sooner than I did.
1st Gear
Joined: Sep 2008
Posts: 125
From: Grand Haven, MI
The pitch was lower, but the frequency sounded the same. It was loudest when the car was accelerating from a stop, and it was less noticeable at speed, but that could have been due to the increased road noise. The piece of steel in the cat that was loose was roughly 3" x 4" in size, but whatever is making the noise on yours sounds like it could be smaller and lighter. Have you checked the metal clips that hold the O2 sensor wires onto the transmission case? If they come loose, the clips land on the cats and rattle (and the wires start to cook).
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