Repairing X pipe to back box flanges

[Adam D]

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 :driving:

Adam

 

[PDJ]

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

 

[PDJ]

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]

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 :roll:

 

[AndyBeech]

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:



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]

If I remember my X pipe was stainless steel

 

[PDJ]

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]

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]

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]

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! :wink:

 

[Adam D]

All fixed using the I6 automotive kit.

 

[srhutch]

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]

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.

 

[srhutch]

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]

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.

 

[AndyBeech]

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.

Yup which was the first option. Pretty much any fabricator in my area weren't particularly interested though and it was always a yeah need to have a look first and then the time and effort to do it (ie. money) made it pointless unless desperately wanted to keep it 'OE' which yields no real benefit. The backbox was practically hanging off in the meantime so didn't really have the time to wait about. The sleeve solution on both exhausts took under an hour while I waited with no messing about or complications. (Only the right hand side exhaust flange had gone but thought may as well just do both while there). Poor old Darragh gave it a good go welding the flanges back up as an emergency fix but there was no chance with the amount of rust on them, would have only been temporary anyway.

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.

It could be. The flange had literally disintegrated and there was nothing to attach the clamps too anymore! I suspect it was the effort to get the old rusted clamps off which had disturbed it enough to be the final nail in the coffin. It was basically only the old rusted on clamps that was keeping it all together pre doing the job.

 

[PDJ]

Pretty much any fabricator in my area weren't particularly interested

I am lucky as can do most things myself TIG welding included.

(Just not spelling)

 

[AndyBeech]

Pretty much any fabricator in my area weren't particularly interested

I am lucky as can do most things myself TIG welding included.

(Just not spelling)

Ha yeah wish I could turn my hand to some of this stuff, would've saved myself a fair bit of money on the way! I guess for fabricators it's the volume of jobs they can get through the door rather than little faffy projects. Glad in hindsight though as saved a fair amount not going that route and just keeping it simple if not an OE fix. Not that it matters, have exhaust valves welded in to both x pipes anyway so far from an OE system anyway!