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Discussion Starter · #1 ·
I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

 

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I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

I hear almost the same on the front right side when going over speed bumps. Sounds like a clunk. Annoying
 

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I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

Here's a possibility: Small Exhaust leak.
If it sounds like a "ticking" driving past fences and highway barriers, that's what it could be. Anything bouncing back the sound at you. I had the same issue and couldn't find the cause until the Infiniti dealer told me I had a small exhaust leak on my Borla Cat-Back exhaust. I took it to a Meineke that had a welder, they used a rubber hose, held it to his ear, and found the small leak. 15 minutes of welding, and $50 later, the ticking was gone.
 

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I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

Catalytic converter heat shield. Seams rust out and they rattle like crazy. Finally fixed mine with ~6" wide strips of galvanized steel, long enough to wrap completely around converter. Secure tightly with long SS hose clamps. There are 4 converters - do them all while you're at it.
 

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I've been trying for months to figure out this rattle from under the right side of my 2004 FX35. I've been under the car wiggling everything to see if I can figure it out, but nothing is loose. I hear it reflecting off the fences in my neighborhood and its much louder on the right side. It only happens when hitting bumps and has nothing to do with acceleration or braking.

I recorded the sound and hopefully I can link that mp3 here for you all to have a listen. Help me infinitifx.org, you're my only hope!

car sounds.mp3

Look up by the exhaust manifold. There is a heat shield that probably rusted and fell against the exhaust pipe
 

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Discussion Starter · #7 ·
Here's a possibility: Small Exhaust leak.
If it sounds like a "ticking" driving past fences and highway barriers, that's what it could be. Anything bouncing back the sound at you. I had the same issue and couldn't find the cause until the Infiniti dealer told me I had a small exhaust leak on my Borla Cat-Back exhaust. I took it to a Meineke that had a welder, they used a rubber hose, held it to his ear, and found the small leak. 15 minutes of welding, and $50 later, the ticking was gone.
Thanks for your reply. I think I should take it to a muffler shop and get their take, since it's not the kind of thing I can put my head next to. I even thought of having a friend drive while I open my door and hang my head under the car. Probably not the smartest idea.
 

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Discussion Starter · #8 ·
Catalytic converter heat shield. Seams rust out and they rattle like crazy. Finally fixed mine with ~6" wide strips of galvanized steel, long enough to wrap completely around converter. Secure tightly with long SS hose clamps. There are 4 converters - do them all while you're at it.
Thanks cycleguy, I'll check that out. Hopefully that's it.
 

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Discussion Starter · #10 ·
Were you ever able to find out what the issue was?
Well I took it to an exhaust shop today and was hoping to have a conclusion to share with you all, but no such luck. It is true that many of those heat shields are rusted through and they have some play in them, but they don't sound like the noise in my recording. The guy removed a broken strap that he thought might be the culprit, but when I drove away that wasn't it. He said he can't weld anything up because the rust will just crumble. So I'm not sure what to do now. It definitely sounds like something in the exhaust, system based on how the sound oscillates. Its got to be something suspended by rubber bushings. But when we were under the car pounding on everything, nothing made that noise!! Makes my sweet FX sound like an old Geo.
 

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Well I took it to an exhaust shop today and was hoping to have a conclusion to share with you all, but no such luck. It is true that many of those heat shields are rusted through and they have some play in them, but they don't sound like the noise in my recording. The guy removed a broken strap that he thought might be the culprit, but when I drove away that wasn't it. He said he can't weld anything up because the rust will just crumble. So I'm not sure what to do now. It definitely sounds like something in the exhaust, system based on how the sound oscillates. Its got to be something suspended by rubber bushings. But when we were under the car pounding on everything, nothing made that noise!! Makes my sweet FX sound like an old Geo.
The fact "that many of those heat shields are rusted through and they have some play in them" says that needs to be addressed. You can't pound or tap on an exhaust system to duplicate the resonance created by a running engine. I've listened to your recording multiple times and it sounds very much like what I had. Try the fix for those shields that I recommended above. It's a cheap DIY as long as you can get the car up on a lift or even reasonable height jack stands.

5-6" wide strips of galvanized steel, long enough to wrap completely around converter (probably ~18" long), about the same thickness used for home air ducts or slightly thicker. You can buy it at Home Depot, Lowes, etc. Master Flow 24 in. x 36 in. Galvanized Steel Flat Sheet-GFS24X361P - The Home Depot

Secure tightly with large SS screw-type hose clamps - 2 per heat shield. 5 in. - 7 in. Stainless Steel Hose Clamp-6799595P - The Home Depot

There are 4 converters - do them all while you're at it.
 

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Discussion Starter · #12 ·
Well its almost a year later and I still haven't resolved this problem. I've clamped every possible heat shield or piece of stray metal that I THINK could be making the noise. I also took it to a second exhaust shop and was informed that it is probably something loose inside the muffler or one of the converters. Since Colorado just adopted California emissions standards, its not a good idea to replace the converters because that would be roughly $5-6k for the new modernized converters. So I'm raising the flag of defeat on this one and I'll just live with the embarrassing sounds from my otherwise very clean Infiniti. I guess eventually something will hard fail and then I'll know what exactly I need to replace. Thanks everyone for your help though.
 
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