Repairing X pipe to back box flanges

Adam D · Post by **Adam D** » Sun Jan 31, 2021 9:25 pm

Hiya,

With my MOT approaching in March I recall a comment from last year that the flanges connecting the x pipe to the rear silencers were looking a bit ropey. Having taken a look with a torch at least one side is fractured through the flange on the x pipe side and the bolts don’t look like they have much life left either. Has anyone used those two piece repair kits you see on eBay to fix them?

The prospect of spending £1.5k to replace the exhaust is

Welcome recommendations for a plug and play x pipe and rear boxes as plan b but would like to try and fix it first.

Thanks in advance

Adam

PDJ · Post by **PDJ** » Mon Feb 01, 2021 11:22 am

Yes just get the £25 set of clamps

You then need to remove the rear back box this makes the next job easier

Then cut grind bend twist the corroded bracket off the back box, this is possible the harder of the two as there is not too much room to get a grinder in without catching the box, pipe or pipe flare. Now cut the one off that is on the X pipe under the car.

Re fit the back boxes to the car the seal is the steel ring this just needs to be clean as do the pipe flares

Fitting the new clamps is just fiddly you will drop them a few times

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PDJ · Post by **PDJ** » Mon Feb 01, 2021 11:25 am

Just looked at the first picture you only need to cut the rusty flange off the picture was from the internal pipe re route job so if you look carefully you can see a cut around the box it’s self this is not part of the flange joint job.

If you are near Manchester or Cleethorpes I can help you out is required

Adam D · Post by **Adam D** » Mon Feb 01, 2021 12:04 pm

Wow thanks for the detailed reply - kindly appreciated!. Do you have a link/company name for those clamps - I’m sure I bought a set from i6 years ago but I cannot find where I stashed them so may need to buy again

AndyBeech · Post by **AndyBeech** » Mon Feb 01, 2021 12:16 pm

Clamps can be got from x8r or Hack Engineering.

Bear in mind this fix only works if the flange parts are not rusted through (mostly likely on the x pipe side) like mine were:

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If they are then the clamps won’t work and you’ll need another solution. Easiest way which I had done was to ‘sleeve’ the back box to the x pipe. Cheap and cheerful and solves the problem permanently.

PDJ · Post by **PDJ** » Mon Feb 01, 2021 1:36 pm

If I remember my X pipe was stainless steel

PDJ · Post by **PDJ** » Mon Feb 01, 2021 1:37 pm

AndyBeech wrote: ↑Mon Feb 01, 2021 12:16 pm Wow thanks for the detailed reply - kindly appreciated!. Do you have a link/company name for those clamps - I’m sure I bought a set from i6 years ago but I cannot find where I stashed them so may need to buy again

Ebay

They all appear to be the same just different prices

AndyBeech · Post by **AndyBeech** » Mon Feb 01, 2021 3:15 pm

PDJ wrote: ↑Mon Feb 01, 2021 1:36 pm If I remember my X pipe was stainless steel

Indeed it is, but I believe it’s the use of mild steel for the OEM clamps that reacts with the SS X pipe and leads to the rusting of the flange parts they attach to. Not a science wizz but I believe there is a technical term for this!
Not the brightest design idea by BMW

GT Spec · Post by **GT Spec** » Mon Feb 01, 2021 7:17 pm

AndyBeech wrote: ↑Mon Feb 01, 2021 3:15 pm
PDJ wrote: ↑Mon Feb 01, 2021 1:36 pm If I remember my X pipe was stainless steel
Indeed it is, but I believe it’s the use of mild steel for the OEM clamps that reacts with the SS x pipe and leads to the rusting of the flange parts they attach to. Not a science wizz but I believe there is a technical term for this!
Not the brightest design idea by BMW

Galvanic corrosion

AndyBeech · Post by **AndyBeech** » Mon Feb 01, 2021 7:39 pm

GT Spec wrote: ↑Mon Feb 01, 2021 7:17 pm
AndyBeech wrote: ↑Mon Feb 01, 2021 3:15 pm
PDJ wrote: ↑Mon Feb 01, 2021 1:36 pm If I remember my X pipe was stainless steel
Indeed it is, but I believe it’s the use of mild steel for the OEM clamps that reacts with the SS x pipe and leads to the rusting of the flange parts they attach to. Not a science wizz but I believe there is a technical term for this!
Not the brightest design idea by BMW
Galvanic corrosion

That's the one!

Adam D · Post by **Adam D** » Sat Feb 20, 2021 11:00 pm

All fixed using the I6 automotive kit.

Post by **srhutch** » Fri Mar 05, 2021 2:47 pm

AndyBeech wrote: ↑Mon Feb 01, 2021 12:16 pm Clamps can be got from x8r or Hack Engineering.

Bear in mind this fix only works if the flange parts are not rusted through (mostly likely on the x pipe side) like mine were:

86C836EC-A2C9-4F85-9861-C77A37C8B785.jpeg69D423C5-E9CA-49C8-9D28-4DABD64955E0.jpeg

If they are then the clamps won’t work and you’ll need another solution. Easiest way which I had done was to ‘sleeve’ the back box to the x pipe. Cheap and cheerful and solves the problem permanently.

I assume you removed the flange off both parts then used a solid sleeve.

Did you have any alignment issues of the rear boxes afterwards?

AndyBeech · Post by **AndyBeech** » Fri Mar 05, 2021 3:17 pm

srhutch wrote: ↑Fri Mar 05, 2021 2:47 pm
AndyBeech wrote: ↑Mon Feb 01, 2021 12:16 pm Clamps can be got from x8r or Hack Engineering.

Bear in mind this fix only works if the flange parts are not rusted through (mostly likely on the x pipe side) like mine were:

86C836EC-A2C9-4F85-9861-C77A37C8B785.jpeg69D423C5-E9CA-49C8-9D28-4DABD64955E0.jpeg

If they are then the clamps won’t work and you’ll need another solution. Easiest way which I had done was to ‘sleeve’ the back box to the x pipe. Cheap and cheerful and solves the problem permanently.
I assume you removed the flange off both parts then used a solid sleeve.

Did you have any alignment issues of the rear boxes afterwards?

Yes flange removed from both and then used a solid sleeve. Will get a picture when the cars back on the road but no issues with alignment or otherwise.
I would have liked to have kept OEM but for the cost there really isn’t any benefit.
It was basically an option of get a fabricator to cut and weld new flanges on to the x pipe at great cost, plus I only found one chap that was actually willing to have a go at it.
Find a good condition second hand x pipe at great cost, and rarely available. Or buy a Supersprint x pipe, again expensive and with no benefit.
Or the option I went with, which was the only one that made sense in the end.
Annoying situation, but ultimately a crap design. I only became aware of it when we changed the clamps as it’s ‘one of those jobs’ and it fell apart after so be aware if you do change them you might well find what I did underneath and there’s no going back!
Should also add underneath mine is fairly spotless rust wise compared to some I’ve seen so seems to be a bit random as a failure point.

Post by **srhutch** » Fri Mar 05, 2021 6:14 pm

I have a spare set of back boxes that have been gutted, and it's the flange on those that have gone.

I also need to check one side of mine as ut's hanging low and I do wonder if the flange has gone on it. I already have the i6 clamps so know it's not the flange itself.

PDJ · Post by **PDJ** » Fri Mar 05, 2021 7:02 pm

If you can get a bit of stainless steel pipe the same size, the flange profile can be shaped on the end and then a short bit welded onto the X pipe and back box.

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