Stainless Exhaust Flanges Rotting Away: What Does the Future Hold?

[packman]

I had a similar situation with my Aunt’s Hyundai Elantra. The flex pipe section on the mid pipe completely rotted off. When I got underneath, I noticed the rear flanges of the mid-pipe were just one glob of rust. I made a failed attempt to drill the bolts out and pull the pipe off. But countless drill bits later, I ended up cutting the flange and buying another flange and a stock mid-pipe. I deliberately left more than enough pipe for the replacement flange to slide over with the intention of cutting bits off for adjustment. I found that the flange slid over the stock exhaust pipe; which made adjusting and bolting the mid pipe much easier. I used band clamps to clamp it together. Came out good for $250.

[IPreferDIY]

Have you tried a mufflerman? ...

It looks like their most easterly one is Cambridge (I'm in the GTA), but I'll be going to Stratford to see Shakespeare's rarely-staged "Henry VIII" (the asshole who killed his wives and took over the English churches and made divorce fashionable), so I'll stop in at a convenient one. I'd be surprised if they were significantly less than $200, and I wouldn't go out of my way to save a few bucks if $200 is reasonable, but it can't hurt to check. Maybe I'll get lucky and they will have lower prices due to being outside of the high-priced GTA. And maybe I'll be feeling better about cash flow by then in any event. Thanks for letting me know.

$200ish sounds about right because you have to buy 4 stainless flanges, bolts, gaskets and then the labor. As I recall when I bought 4 stainless flanges alone from Zoro it was close to 100 bucks. Anything stainless and price rises exponentially.

One other place you could try is Toronto muffler and brake (Hot Rod Scott's). They did complete stainless exhaust for my 96' back in the day which I am still rocking on the 85' with mods. It was quite reasonable but that was years ago.

Considering that one place said $240 (I would guess that place was comparable to Scott's), $200 was certainly an improvement. I imagine there's a lot of mark-up though. Ideally, I would like to re-use the stainless fasteners that I put on, and maybe even two of the best of the five or six (total) thin Victor Reinz (supposedly OEM) gaskets that I tried using to prevent any gaps during my latest futzing with it, but I can certainly appreciate why a shop would not do that (though I hope they would at least use anti-seize if I brought some). I don't have any meaningful welding experience, so NFC about time required, but if $200 is considered reasonable overall, I'll just work it into my future finances. I have U-joints on order and a bigger-than-usual monthly bill coming up (not to mention an annual income tax setback arising from my independent contractor work), so the flanges are not a priority.

[IPreferDIY]

I looked into this stuff a bit and found that a significant issue with doing flanges is warpage. There's also an issue of getting an undesirable weaking of the weld if the heated metal is exposed to normal air. I saw something about someone avoiding both problems by attaching a stainless flange to an aluminum flange that has a short bit of closed aluminum pipe through which argon can be introduced.

Building on this, I came up with a couple of ideas that might be useful (if they are actually novel) for those who work in the field:

1. In order to minimize the amount of argon needed, one could use some kind of rubber plug or whatever that could be inserted into the pipes and expanded to create a seal. By doing this, one could possibly even limit the argon to what is necessary to purge the air and then close the outlet without having to leave the argon flowing (which seems to be the typical method).
2. For two mating flanges, one could create a really thick aluminim flange to which both stainless flanges could be bolted and into which argon could be introduced. Since argon is reportedly heavier than air, the inlet could be on the bottom and the outlet on the top.

For our set-up, one could insert the plugs and weld the two flanges, then unbolt the flanges and take the plugs out. I suppose there might be alignment tweaking required for the other side, but I'm sure the people who already do this work could figure that out. I suppose one could even have both sides set up at the same time (i.e. four rubber plugs and two aluminum parts). I would think a thick enough gasket would compensate for any lack of perfection in the alignment that might result from using and removing the thick aluminum pieces.

I imagine just the prep work would be a significant aspect of the job. If I was to try the ultra-cheap route of simply cutting off the flanges and clamping on joiners, I would resort to using a hacksaw while on my back. Does anyone know what the actual cutting process involves? My limited familiarity with welding has been in a machine shop setting where things are machined nicely, which obviously can't happen in this context.

[GM_Guy]

There is no need to try and save argon, the argon needs to sheild your arc, whats happening on the other side of the material is irrelevant (other than wind).

So what kind of flanges have you got anyway? Just the flange itself, or stub pipes with flanges attached? If the first, I can see why nobody wants to touch it, thats a pain.

[IPreferDIY]

Here’s a video that explicitly demonstrates the results of using and not using argon on the backside of the weld, with the final ‘show and tell’ being around 11:10:



Before that part, he also demonstrates an interesting weld-cleaning gizmo.

What concerns me about the people who just weld in pieces of pipe is that it’s highly doubtful that they use argon inside the pipes. Dunno to what extent their welds would be weaker, but I would prefer it being done properly.

Here’s an interesting video showing how much warpage one gets from even a 1/2" stainless flange despite using an aluminum block (with argon on the backside), with the final ‘show and tell’ being around 14:20:



The flanges are not something I would bother bringing with me in this context. I would presume they would use whatever works for them.

[GM_Guy]

If you think you will find an exhaust shop that does that, well, good luck to ya.

Alex.

[IPreferDIY]

A more significant issue for me is if one shop thinks they can charge an extra $40 without doing anything extra, then no thanks. It could be that the lesser-quality weld is not significant in our particular application, but that's beyond me at this point.

[IPreferDIY]

I had a chat about this with my father, who has experience welding stainless for food industry applications. Apparently back-purging is only an issue for butt connections, in which case the weaker weld and reduced corrosion protection from no back-purging would be a concern. If there is an overlap, then back-purging isn't really an issue. I'm not suggesting this must be right but rather just adding it to the mix.

It seems the vast majority of stainless flanges do not have any kind of protrustion for a butt weld, so I guess they're intended for an 'overlap' weld, like so:



I would also guess the folks who weld in pieces of pipe are probably doing sleeves for overlap welds rather than butt welds. This makes sense, since getting butt welds aligned with small enough gaps would seem exceedingly difficult, and it's hard to imagine shops knowingly doing weaker welds. OTOH, I'm having a hard time justifying $160 for welding on a couple of sleeves (even if $200 for the flanges might still not be so bad).

[Mr Bean]

You are overthinking it. They are just flanges. You are not building Titanic here.

[IPreferDIY]

Maybe you can afford to throw $200 at something without regard to whether it will last for two years or 10+, but I can't. And given that no one here seems to have any expertise in this area, maybe others would find it interesting.

[GM_Guy]

While I appreciate the fact you want something done right, its an exhaust system with thin walled pipe, not a food processing plant or refinery with heavier pipe, and are more precisely laid out. Its an exhuast system that mostly fits together and gets welded or clamped. Butt welded gaps with excess gap get filled with more filler rod. You get them as close as possible then close them up.
You dad a mobile welder? Go pay a visit and have him weld it up.

[IPreferDIY]

...
You dad a mobile welder? Go pay a visit and have him weld it up.

Do you really think this thread would have gotten to this point if that was the case?

For those who would rather just pay someone to do it and not worry about the finer points of welding, do what you like, but why blow off anything more than the most superficial understanding of welding as something not worthy of understanding? I'd love to learn to weld, not only for messing around with stuff, but also as an interesting supplement to my science background. I would certainly do the flanges myself if I was in a position to do so. One concern is whether a shop would actually disconnect the battery during welding, which should be done to protect the electronics. With my luck, I'd end up with someone who either doesn't know, doesn't give it any thought, or just doesn't bother.

I managed to stop by Mufflerman two hours before closing time yesterday (traffic was nasty), but they seemed rather busy and probably would not have been able to get to me even if they were not the type of place that only puts in pieces of pipe. Their “ballpark” estimate for pieces of pipe was $200. So much for lower prices outside the GTA. It's probably been about two decades since I had work done at Zoro, and they win again.

[IPreferDIY]

Finally got this done at Zoro. $200 plus taxes. After all the lead-up, it went really quick. Before I went wandering around, the guy said it would take about half hour. So if it's a typical $100/hr shop rate, there must be a pretty hefty profit.

I figured I would be nice and provide the right wrenches for the flange bolts I used and the right socket on my ratchet for the battery cable, plus some antiseize for the new hardware. I happened to have a computer power supply box that I didn't need and used that. I was also wanting to get the old parts back but didn't get around to mentioning that. The guy pointed out he had a toolbox with the necessary tools, as if I had done something foolish.

By the time I got back, the guy had gone for lunch or whatever, and he hadn't put the old parts in the box. It turns out that he hadn't disconnected the flanges at all but rather just cut maybe an inch or so on either side of them and dropped them in the trash can. Whatever. At least it's done, and there is a noticeable difference while driving. I noticed a vibration while stopped or close to stopped at certain points, and I would guess the weights would dampen that if I put them back on, but meh.

The Costco in that part of Mississauga has a self-serve checkout at one end, so I guess they'll be offering that in other locations soon.

[IPreferDIY]

I was hoping I wouldn't have further exhaust issues, but the hardware holding the passenger side cat to the exhaust manifold rotted away enough for the cat to drop a bit. Got new hardware put in for $150 plus taxes at Zoro without bothering to call around. I'm figuring the other side should be fine for at least 1-3 more years.

Here's a pic of the H-pipe flanges:



Apparently their flanges rotate on the stubs before installation and get welded once aligned.

[IPreferDIY]

Something possibly worth noting is that while I dozed in the waiting area for a couple of hours, I was able to get a sense of their business model. They generally don't have to deal with fluids or functional problems, since their customers generally have functioning vehicles that only need the exhaust work. That seems to take away a lot of aggravation from working on cars.