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Joined: 15 Jul 2019
Posts: 73
Location: Somerset

PostPosted: Wed Jul 17, 2019 11:28 pm    Post subject: Exhausts .... Bottom seam splits ... Weldable? Reply with quote

996 C2 3.6 2003

New car, first 911, full of questions!

Bottom seam on both boxes are splitting, (knew about this when buying, so it's not an unpleasant surprise) .. Splits, as opposed to missing metal...how long might they last?

Question: Has anybody successfully welded them? In the knowledge that you can't weld on rust, how much of the seam should be removed to effect a decent repair? Concerned that removing too much might loosen internal baffle plates .... Have no idea what is or isn't sandwiched between the two halves being joined at the seam. Any experience out there?

I have access to an expert stainless welder, but would like to be able to give him some guidance.
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Joined: 12 Mar 2016
Posts: 79

PostPosted: Thu Jul 18, 2019 1:58 am    Post subject: Reply with quote

I'm pretty sure they are hosed by this stage. I did hear of someone welding them up and failed again after a few months.

Would be interested to hear otherwise, its a wallet-emptying experience replacing both mufflers.
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Fast & Furious
Fast & Furious

Joined: 04 Oct 2010
Posts: 8557
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Thu Jul 18, 2019 2:26 am    Post subject: Reply with quote

I repaired a seam on mine I was able to weld together where it had cracked but I had one little section that was too wide so I bridged it with a narrow piece of stainless and it welded fine. I did this with my hobby MIG with stainless sheet/wire, it wasn't pretty but did the job, if you have access to better kit it should be doeable.

Don't split the seams all the way around if you don't need to, just do it in sections so you keep it mostly closed up. There is not a lot inside them really so you won't need to worry about damaging anything internally.

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Joined: 22 May 2016
Posts: 386

PostPosted: Thu Jul 18, 2019 5:57 am    Post subject: Reply with quote

Some people add strength to the seam when welding with a U section piece of metal strip. When mine were welded the guy just used a lot of MIG wire!

Although you say “split” I assume there must be some corrosion. They tend to go because they are in the firing line of the rear tyres and water collects in and around the seams. They also rot from the inside out as all exhausts do. If there is corrosion it can be anywhere on the seam, so removal to get access for welding is the only way to do a thorough job.
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Joined: 15 Jul 2019
Posts: 73
Location: Somerset

PostPosted: Thu Jul 18, 2019 8:05 am    Post subject: Reply with quote

Yes, Grifter, there is of course corrosion under the splits, probably a whole lot more than is currently visible.

I guess I am trying to decide whether the u-section approach is best, which might trap all this corrosion inside....

Or whether to cut off all the protruding seam so that I (not me, but my welder) can attach a 'bandage' strip, say an inch or more wide along the length of the bottom (only) joining seam.

Looking at how the fixing brackets are welded on .... There would seem to be enough thickness to weld on.

Anyone prepared to comment on the various after market exhaust brands?
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Joined: 20 Jan 2018
Posts: 406
Location: Beds/Bucks

PostPosted: Thu Jul 18, 2019 8:20 am    Post subject: Reply with quote

I welded the seams on a set of 3.6 boxes I was experimenting with.
The metal is very thin (or at least was on mine), so needs care, otherwise its easy to burn through.
I found it best to 'sleeve' the seems ('u' shape), so I could weld further away from the corroded area and get a better weld. I didnt try the 'bandage' method.

Overall though, it wasnt a great job. But I was only playing with these boxes, as I already had a set of new boxes to go on.
2002 996.2 C2 Cabriolet
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Joined: 25 May 2015
Posts: 150

PostPosted: Thu Jul 18, 2019 2:05 pm    Post subject: Reply with quote

A little more experience to add to the correspondence!
My 2004 car boxes had what seems to be the usual corrosion,mostly on the bottom seams but no leaks.
I bent up some fairly light gauge material and oxy/acy welded this in place. This left a cavity between the new section and the original seam which I filled with heat resistant silicone and the result has been good for 3 years now, although I am geared up to replace the boxes at some stage! (probably Spyder or TopGear for the valved system)
The silicone had proved able to resist the temperatures with no problems, found it by trawling the net.
If anyone wants to have details let me know, I think I still have the remainder of the cartridge.
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Joined: 08 Jun 2019
Posts: 32
Location: Finland

PostPosted: Thu Jul 18, 2019 6:34 pm    Post subject: Reply with quote

Mine were split when I bought it and got worse in a few months. I welded them, but the repair only lasted about one season. I had to replace them this year to pass MOT. Luckily I found a set of really nice OEM PSE back boxes!
996 Carrera 4 Coupe
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