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Exhaust - cat flange to rear system bolts/nuts/gasket


Jago

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Hey guys and girls ! 
 

Naomi was driving the car today and unfortunately the exhaust began to blow ! Upon later inspection this evening I appear to have found the problem… it looks like the lower bolt/nut on the left bank where the cat flange is (behind the wheel) where it mounts to the over swing arm section has a bolt missing/come loose and the gasket is hanging low. 
 

now I’m assuming this a pretty simple fix (replace the bolt/nut) I think it’s an M8x30 with an M8 hex nut. Advise on changing the gasket too ? It looks in pretty decent nick just a bit sooted up ? Checked the other and they look like they have been replaced with stainless nuts/bolts 
 

cheers 

 

51589776834_3f1f6867bf_b.jpg51589776849_58abe80265_b.jpg

 

Edited by Jago
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Sadly it's a common issue and it should have been picked up and reported to you during your regular inspections. You can guarantee the other side won't be far behind so you really should tackle both because the bolts are made of chocolate and corrode away.

You may need to do some cutting and then gently tap what remains out.  I'd source some alternative bolts and yes probably best to replace the gaskets since you are there.

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7 hours ago, Nobbie said:

I’d just replace the nut and bolt and see how it went. No obvious damage to the gasket.

7 hours ago, daz05 said:

Sadly it's a common issue and it should have been picked up and reported to you during your regular inspections. You can guarantee the other side won't be far behind so you really should tackle both because the bolts are made of chocolate and corrode away.

You may need to do some cutting and then gently tap what remains out.  I'd source some alternative bolts and yes probably best to replace the gaskets since you are there.

I’ll get the nuts and bolts today from work and order the new gaskets along with some fire gum too. 
 

do you know what the part no is and where to pick a pair gaskets from ? Have any links ? Be much appreciated 

 

thanks ! 

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Sheffield Porsche dealer if you can pick up, or Design 911 if you want it posted out. They have diagrams on their site where you can work out the part number.

This looks like the part if your’s is a 981

https://www.design911.co.uk/fu/prod133359/Porsche-981-Boxster-Cayman-Exhaust-Gasket-Manifold-to-Muffler-98111111300/

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58 minutes ago, Nobbie said:

Sheffield Porsche dealer if you can pick up, or Design 911 if you want it posted out. They have diagrams on their site where you can work out the part number.

This looks like the part if your’s is a 981

https://www.design911.co.uk/fu/prod133359/Porsche-981-Boxster-Cayman-Exhaust-Gasket-Manifold-to-Muffler-98111111300/

HI Nobbie, That's the one ! 

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The oem arrangement is for pressed fit bolts in the cat side and nuts on the muffler side. As Daz suggests, these are made of chocolate (I suspect the main issue is their location probably results them being regularly coated in road grime/water/salt etc) it’s unlikely this particular issue would occur because they just rust and rot away instead. It’s lucky for you if these have already been replaced with stainless steel so you just need a replacement nut and bolt (and maybe gasket).  

I guess the question is how do you stop this happening with replacement Stainless bolts as different materials subject to heat cycles and vibration could always result in this outcome!

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22 minutes ago, Greenman said:

The oem arrangement is for pressed fit bolts in the cat side and nuts on the muffler side. As Daz suggests, these are made of chocolate (I suspect the main issue is their location probably results them being regularly coated in road grime/water/salt etc) it’s unlikely this particular issue would occur because they just rust and rot away instead. It’s lucky for you if these have already been replaced with stainless steel so you just need a replacement nut and bolt (and maybe gasket).  

I guess the question is how do you stop this happening with replacement Stainless bolts as different materials subject to heat cycles and vibration could always result in this outcome!

I believe they have been changed from looking at the other side. The nuts I could see was silver and clean/good nick so assuming they have been replaced. I've ordered a pair of gaskets from Design911 too. 

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If it's already fallen out, it's saved you the effort to grind it apart.  

As Daz says, do all the nuts, bolts, gaskets etc at the same time so you know where you are then.

Check you fixings materials too so as you're not encouraging further corrosion.

Edited by GTSMarky
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29 minutes ago, GTSMarky said:

If it's already fallen out, it's saved you the effort to grind it apart.  

As Daz says, do all the nuts, bolts, gaskets etc at the same time so you know where you are then.

Check you fixings materials too so as you're not encouraging further corrosion.

picket up some stainless bolts and nuts from work just now so that should alleviate the corrosion. got some copper grease too to coat the threads. 

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Funny co-incidence , wife phoned on the way home an hr ago and said the cayenne was gurgling and very loud so couldn’t drive it….

 

new style PSE 

[url=https://ibb.co/2dZrtwb][img]https://i.ibb.co/2dZrtwb/7-E75-CB8-A-6-BA0-41-A6-8768-7-DF24-B1098-A8.jpg[/img][/url] [url=https://ibb.co/HH81XPD][img]https://i.ibb.co/HH81XPD/893-D773-D-B3-DA-4-FEE-AF02-E576-E798939-A.jpg[/img][/url] [url=https://ibb.co/16MJ2v5][img]https://i.ibb.co/16MJ2v5/38-FC2-B9-F-EBBE-4616-ADC8-89-D92-F24-F300.jpg[/img][/url]

Edited by zagamuffin
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12 hours ago, Jago said:

Fixed it with the bolts and checked the other side until the gaskets arrive next week then will swap for high tensile 

You don't need high tensile bolts for these flanges. They are not a high stress connection like a suspension bolt. Stainless steel is more than adequate. Although, as others have said, stainless bolt with brass nut would be best as it is less susceptible to galling - welding together through heat cycles. The thing is, that part of the exhaust is not a bit that gets super hot like the exhaust manifold. 

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3 hours ago, The Caped Crusader said:

Nope. The bolt is M8 so the commensurate torque required would be around 25nm. I've never had any issues using them. 

I've just checked the workshop manual and the correct torque is 23Nm (17 ftlb). 

 

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On 10/16/2021 at 8:23 PM, The Caped Crusader said:

I've just checked the workshop manual and the correct torque is 23Nm (17 ftlb). 

 

The manufacturer specified torque setting of 23Nm is correct for the OEM fasteners, but not for the other mix & match materials mentioned in this post. Stainless, brass and chocolate, to name a few😁

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On 10/16/2021 at 4:25 PM, The Caped Crusader said:

Nope. The bolt is M8 so the commensurate torque required would be around 25nm. I've never had any issues using them. 

I see, they are skinny!!  Will get some nuts and gaskets ordered up for a "winter weekend project" when time allows 👍

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