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#4458129 - 07/13/17 10:57 AM Fasteners on exhaust systems
greasegunn Offline


Registered: 01/01/12
Posts: 202
Loc: NY
I've search the internet but I can't seem to find a good answer so I've turned to the wisdom of the Forum.

A stud has broken off on the flange between the muffler and the exhaust pipe. I plan to simply drill out the stud and replace with a nut and bolt. What I'm not clear on is if a special grade or alloy of fastener is preferred or required. This is on the stock exhaust of a 2012 Mazda 6. Thanks for your help.

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#4458145 - 07/13/17 11:09 AM Re: Fasteners on exhaust systems [Re: greasegunn]
jjw6455 Offline


Registered: 03/06/14
Posts: 4
Loc: ohio
Something non rusting (stainless ?).

ENGINE AND ENGINE COOLING : EXHAUST SYSTEM
Number 10097841
NHTSA Item Number 01-025-12-2699
Date 2017-04-25
Summary Some vehicles may exhibit an exhaust leaking noise from the rear of the vehicle. The noise may be caused by a gap between the exhaust hanger bracket and flange, which allows moisture to enter and cause the exhaust studs to rust and possibly

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#4458168 - 07/13/17 11:34 AM Re: Fasteners on exhaust systems [Re: greasegunn]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
The shops often blow the stud out with a torch. Makes an ugly hole but it works.

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#4458189 - 07/13/17 11:50 AM Re: Fasteners on exhaust systems [Re: greasegunn]
Trav Offline


Registered: 11/20/06
Posts: 18825
Loc: MA, Mittelfranken.de
If you drill right through use a high grade bolt, stainless doesn't have as much shear strength but you can use a stainless or copper nut and stainless washer. Next time just blow the nut off with a torch if you cant get it off.


Edited by Trav (07/13/17 11:51 AM)
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#4458193 - 07/13/17 11:53 AM Re: Fasteners on exhaust systems [Re: greasegunn]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1810
Loc: Saskatchewan, Canada
Because the muffler is reasonably far from the highest heat areas, you have some options. Distance from the catalytic converter is key ... it's the last high heat component of the exhaust. Three or more feet and you should be OK with a wider choice of fastener.

You can try a regular steel bolt and nut, use anti-sieze on it but don't expect that to last long with the temps experienced. Grade 5 should be good and many systems use plain grade 3 at the back of the exhaust.

If appearance is important use stainless but they are not as strong as a high grade steel fastener. Brass is an option but be careful, they fail at a relatively low torque. However brass is least affected by corrosion.
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#4458230 - 07/13/17 12:35 PM Re: Fasteners on exhaust systems [Re: greasegunn]
28oz Offline


Registered: 04/20/17
Posts: 334
Loc: Utah, USA
Right or wrong, I've always used grade 8 hardware when replacing anything exhaust-wise. Never had an issue with it.
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
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#4458242 - 07/13/17 12:49 PM Re: Fasteners on exhaust systems [Re: 28oz]
Lubener Offline


Registered: 01/22/11
Posts: 2574
Loc: N.Ohio
Originally Posted By: 28oz
Right or wrong, I've always used grade 8 hardware when replacing anything exhaust-wise. Never had an issue with it.


Most shops use grade 2. I never heard anyone having issues with exhaust fasteners breaking on their own.Maybe after many years.


Edited by Lubener (07/13/17 12:51 PM)
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#4458248 - 07/13/17 12:58 PM Re: Fasteners on exhaust systems [Re: greasegunn]
Linctex Online   content


Registered: 12/31/16
Posts: 6146
Loc: Waco, TX
Any steel bolt will work, and should last nearly 10 years. You must have a LOT of salt!

No need to go exotic.


Edited by Linctex (07/13/17 12:58 PM)
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#4458293 - 07/13/17 01:55 PM Re: Fasteners on exhaust systems [Re: greasegunn]
andyd Online   content


Registered: 09/25/04
Posts: 7125
Loc: Marshfield , MA
I use grade 2 hardware. I replace the U Clamps and hope they shear after a few yanks
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#4458296 - 07/13/17 01:59 PM Re: Fasteners on exhaust systems [Re: Lubener]
28oz Offline


Registered: 04/20/17
Posts: 334
Loc: Utah, USA
Originally Posted By: Lubener
Originally Posted By: 28oz
Right or wrong, I've always used grade 8 hardware when replacing anything exhaust-wise. Never had an issue with it.


Most shops use grade 2. I never heard anyone having issues with exhaust fasteners breaking on their own.Maybe after many years.


Grade 2? Might as well use zip ties! Joking..... I use grade 8 'cause if it's worth doing, it's worth over-doing. laugh
_________________________
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
2003 Ford Excursion 7.3 PSD - Mobil 1 TDT 5w-40

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#4458312 - 07/13/17 02:12 PM Re: Fasteners on exhaust systems [Re: greasegunn]
Kestas Offline



Registered: 06/04/02
Posts: 12321
Loc: The Motor City
I wouldn't use anything over Grade 2. Strength is not the issue. Getting it apart when it's rusted solid is the main concern. It's easier to cut or drill soft fasteners.

What is the benefit of using Grade 8?

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#4458327 - 07/13/17 02:21 PM Re: Fasteners on exhaust systems [Re: Kestas]
28oz Offline


Registered: 04/20/17
Posts: 334
Loc: Utah, USA
Originally Posted By: Kestas
I wouldn't use anything over Grade 2. Strength is not the issue. Getting it apart when it's rusted solid is the main concern. It's easier to cut or drill soft fasteners.

What is the benefit of using Grade 8?


Talked to a muffler shop about it once and that is what they used and recommended. I'm no metallurgist, but there might be more corrosion resistance perhaps? Lower grades would definitely be easier to cut or drill, but if a stronger bolt/nut doesn't break, you wouldn't need to cut or drill to begin with. I could be completely wrong, but it's worked for me.
_________________________
-----------------
1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
2003 Ford Excursion 7.3 PSD - Mobil 1 TDT 5w-40

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#4458337 - 07/13/17 02:32 PM Re: Fasteners on exhaust systems [Re: 28oz]
Kestas Offline



Registered: 06/04/02
Posts: 12321
Loc: The Motor City
Originally Posted By: 28oz
I'm no metallurgist, but there might be more corrosion resistance perhaps? Lower grades would definitely be easier to cut or drill, but if a stronger bolt/nut doesn't break, you wouldn't need to cut or drill to begin with. I could be completely wrong, but it's worked for me.

I am a metallurgist. Grade 8 offers no more corrosion resistance than a Grade 2. In fact it may even be worse.

You don't cut and drill because an exhaust system bolt breaks, you do it because it is rusted solid.

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#4458352 - 07/13/17 02:51 PM Re: Fasteners on exhaust systems [Re: Kestas]
28oz Offline


Registered: 04/20/17
Posts: 334
Loc: Utah, USA
Originally Posted By: Kestas
Originally Posted By: 28oz
I'm no metallurgist, but there might be more corrosion resistance perhaps? Lower grades would definitely be easier to cut or drill, but if a stronger bolt/nut doesn't break, you wouldn't need to cut or drill to begin with. I could be completely wrong, but it's worked for me.

I am a metallurgist. Grade 8 offers no more corrosion resistance than a Grade 2. In fact it may even be worse.

You don't cut and drill because an exhaust system bolt breaks, you do it because it is rusted solid.


I've drilled out plenty of broken studs. Anyways, fair enough. You're a metallurgist, so I will defer to your opinion. I'm completely open to being told I'm wrong, lol. That's how you learn, right? The grade 8 hardware I've replaced still looks brand new after a couple years whereas others have rust very shortly. shrug
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
2003 Ford Excursion 7.3 PSD - Mobil 1 TDT 5w-40

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#4458364 - 07/13/17 03:03 PM Re: Fasteners on exhaust systems [Re: greasegunn]
E365 Offline


Registered: 12/16/07
Posts: 448
Loc: USA
What's the take on nickel based anti-seize compounds on exhaust hardware? The super high temp stuff. I've used it lately, but not long enough to know if it really helps long-term.
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