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#4812231 - 07/12/18 12:32 PM Is this rattle/buzzing noise just my exhaust leak?
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
video - works best with headphones (ignore my dumb voice, lol)
Sorry, audio is lousy, lots of wind/road noise, I don't have any good recording gear.

2004 Infiniti G35, 6 speed manual, totally stock. I know I have an exhaust leak (flexpipe is a bit frayed in places and some gaskets could probably use replacing).

It tends to only be audible when:
- up to temperature
- under load
- between 2k and 2.5k rpm

Sometimes, I can hear it a little bit in that same rev range in neutral, and sometimes I hear a very faint quick buzz when the revs are winding down (ie.: not under load). It's heard best when driving next to a tall curb. Can't ever hear it in the garage.


Edited by OCDriver (07/12/18 12:35 PM)

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#4812385 - 07/12/18 03:38 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
28oz Offline


Registered: 04/20/17
Posts: 383
Loc: Utah, USA
I would check all the heat shields and brackets that connect to the exhaust. My VQ Quest had a similar low rpm/under load buzzing/rattle. Still chasing it a little bit, but most of it was caused by cracked exhaust brackets. Sometimes you have to actually take them off to see the cracks/breaks.
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#4812410 - 07/12/18 03:55 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
Trav Offline


Registered: 11/20/06
Posts: 19284
Loc: MA, Mittelfranken.de
Look carefully at the brackets going to the cats, cracks are common. they can be reinforced and welded and last ad infinitum.
Don't be surprised to find it adding fuel at a high rate with a CEL every time the crack opens at some point, also common.
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#4812413 - 07/12/18 03:59 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: Trav]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
Thanks, I'll have to raise it and take a look.

Quote:
Don't be surprised to find it adding fuel at a high rate with a CEL every time the crack opens at some point, also common.

Never had a CEL on this car, fuel economy is exactly where I'd expect it to be.

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#4812534 - 07/12/18 06:40 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
Trav Offline


Registered: 11/20/06
Posts: 19284
Loc: MA, Mittelfranken.de
Sorry I meant to say eventually throw a CEL, if the crack gets larger pre cat its a distinct possibility on these.
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#4812548 - 07/12/18 06:50 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
Got the car up on jacks right now. This is a little odd...



This bracket is bolted to the transmission (middle two bolts), but the bolts on the ends aren't actually connected to anything. They look like they were maybe once there as a brace for the cats and/or heat shields?

EDIT: Referred to the Haynes manual. That's exactly what they are. There are supposed to be two bushing-like pieces there attached to what is currently a non-existent portion of the heat shield.

Any ideas for a cheap, temporary-ish fix without spending obscene amounts of money on new cats?

Heat shields are also quite corroded:



Also this:
https://streamable.com/p0hd6


Edited by OCDriver (07/12/18 07:02 PM)

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#4813031 - 07/13/18 09:36 AM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
funflyer Offline


Registered: 06/26/14
Posts: 708
Loc: Northern Arizona
What's your definition or "obscene money"? Aftermarket cats for your car seem pretty reasonable to me and they look like something a DIYer should be able to replace without the need for a muffler shop. Here are a few, of the many available sets, on ebay. Unless you go with OE, these are probably what you'd get at any muffler shop.


Cat

Cat


Edited by funflyer (07/13/18 09:37 AM)
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#4813181 - 07/13/18 01:11 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
Lubener Offline


Registered: 01/22/11
Posts: 2604
Loc: N.Ohio
BZZZZZZZZZZZ
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#4813308 - 07/13/18 03:25 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
Trav Offline


Registered: 11/20/06
Posts: 19284
Loc: MA, Mittelfranken.de
Yep that what I expected. You can see where the crack is developing right before the front wide band. That is what will cause a CEL probably sooner than later.
You remove the cat and the bracket, cut the shield away and remove the bracket remnants from the pipe.
clean the pipe up well so it can be welded properly.

Weld the crack if present and grind it down smooth then take a piece of pipe and cut it in half lengthwise. Place this over the crack so it has about 1" overlap around the crack or where the broken piece of the bracket was, weld it all the way around.

Now fab an end for the bracket or weld it or repair, whatever it takes to reattach it.
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#4813312 - 07/13/18 03:32 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
So, I've removed the bracket that was doing nothing and put hose clamps around the heat shields that were coming loose. Hasn't made a difference.

I can't find any hangers that are loose or anything. Any bright ideas?

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#4813698 - 07/14/18 06:52 AM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
Trav Offline


Registered: 11/20/06
Posts: 19284
Loc: MA, Mittelfranken.de
Sure but you need a lift to do it, I wouldn't go under the car with it running on jack stands.
Put the car on a lift with someone in it to operate the throttle while you pull on the pipes and try to move them, sometimes it takes a little movement of the pipes to hear it.
Check every heat shield, you can silence a suspected vibrating one temporarily with a small stone jammed between the cat/pipe and shield.
_________________________
ASE L1, Master. Deutsch Meisterbrief.

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#4813798 - 07/14/18 09:57 AM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: Trav]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
Quote:
You can see where the crack is developing right before the front wide band.

Oh yeah, I can see how it looks that way in the picture, but that's just shadows. On visual inspection, only the heat shields have cracks. The cats are solid with no cracks.

Quote:
Sure but you need a lift to do it, I wouldn't go under the car with it running on jack stands.
Put the car on a lift with someone in it to operate the throttle while you pull on the pipes and try to move them, sometimes it takes a little movement of the pipes to hear it.

That's the tricky part. It only seems to happen under load. Idling and revving doesn't rarely produces the noise.

I got the car up again today. After reviewing some photos of what a "good" exhaust should look like on this car, I can clearly see where the cats originally had a welded piece (now corroded to nothing) with a hole to attach a nut and bolt to the brace.


Edited by OCDriver (07/14/18 10:02 AM)

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#4813863 - 07/14/18 11:51 AM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
As a temporary fix / test, I reattached the brace to the transmission and fastened the cats to the brace's L-brackets on the ends using a hose clamp.

Still noise...

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#4815054 - Yesterday at 07:43 PM Re: Is this rattle/buzzing noise just my exhaust leak? [Re: OCDriver]
OCDriver Offline


Registered: 04/13/16
Posts: 90
Loc: Canada
Ah-ah?
That third part where I'm tapping is the flexpipe in the y-pipe.


Edited by OCDriver (Yesterday at 07:43 PM)

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