Exhaust info needed

Exhaust info needed

Postby Wiley [OP] » June 25th 2020, 9:00pm

tldr; Suggestions? I am an exhaust noob.
Should I leave the y pipe bolts/donuts alone?
Should I change out all pipe/catalytic converts now while the van is apart?
I would prefer to do it all now.


Hey, I took off my exhaust/tail pipe due to a hole or two in it, and I wanted to get up behind it to sand the under body. The exhaust pipe is rusted from the manifold to end pipe, ie it is all rusted. How do I know when it needs to be replaced vs just covered in surface rust? When do catalytic converters need to be replaced, same with the donuts at the end of the y pipe? I need to change my o2 sensors which will require some heat, so was wondering if this is a good time to just change everything from the lower manifolds out, I don't mind the cost so much as maybe I shouldn't mess with too much now. I can't weld, but have someone onsite who can, or I can use clamps until I get to someone who can.


Thanks
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Re: Exhaust info needed

Postby WoodButcher » June 26th 2020, 2:39am

Stock replacement, no welding. I did my '97 2wd years ago from the maifold back w/ all the sensors. At the laps it was almost 1200 bucks, at rock auto you will fare much better I'm sure.
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Re: Exhaust info needed

Postby markmitch » June 26th 2020, 5:09am

Best way to check it in a rust situation is climb under with it running and have someone take a potato and hold it against the opening. you will see any leaks or hear them. It may take a few times with you crawling around under there to see the whole thing. each time you move to see other sections take the potato away or it may stall the engine. Yeas ago I lived in Maine and worked at a garage and this is how the mechanic checked for leaks. I am sure there are other ways but this is what I seen.
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Re: Exhaust info needed

Postby Big_kid » June 26th 2020, 1:39pm

Potato, helper with a rag, whatever seals the opening. We'll be doing this to the new to us Mazda pretty soon too.
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Re: Exhaust info needed

Postby markmitch » June 26th 2020, 2:08pm

If you decide to replace all the exhaust I recommend a fully welded turbo muffler from Summit, it is not loud it just has free flow compared to the stocker. Then get the walker tail pipe from o'reilly's auto parts pn 44471. It can be found online too. This tail pipe is 2.5 inches compared to the others available which cost more or about the same. Lets your engine breath better.
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Re: Exhaust info needed

Postby petema » June 26th 2020, 4:10pm

I haven't tried I myself, but I read about someone using a reversed vacuum cleaner to create a low overpressure in the exhaust pipe. With less noise, its easier to hear tiny leaks. P
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Re: Exhaust info needed

Postby augidog » June 26th 2020, 8:07pm

Big_kid wrote:Potato, helper with a rag, whatever seals the opening. We'll be doing this to the new to us Mazda pretty soon too.
at the undercar shop, a welding glove was our choice. it only takes a second to find most leaks, and a visual search for carbon buildup was effective as well.

under good conditions the piping before the converter(s) stays hot and dry, and aluminized exhaust was a game changer as well...it's difficult to give generic advice. the condition of the manifold donuts and studs would help me decide. if they need attention, that would be the time to consider a new y. if the y-pipe's never been loose and moved around, and never leaked, I'd leave it alone and use it until it developed an actual hole.

my original y has a universal converter welded in, the studs are pretty clean for 25 years old, and it had enough meat to weld a new exhaust pipe to it. from there I had an OE-specced generic muffler and walker tailpipe clamped on.


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Re: Exhaust info needed

Postby Wiley [OP] » June 26th 2020, 9:57pm

Awesome, thanks guys, the van isn't going to be running for awhile, so I will probably dive right in even if catalytic converters are still good, only a matter of time before they need replacing. Headers are just as rusty, would you stop at replacing the y pipe, or keep going and replace the gaskets to the headers, or even replace the headers also? Already replacing the manifold gasket so stuff is out of the way. Thanks!

Founds a thread which has been helpful, posting for others who find their way to this one:
HEADERS!! HEADERS!! HEADERS!!
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Re: Exhaust info needed

Postby Onthewater01 » June 26th 2020, 11:53pm

Hey Wiley,

I just replaced my exhaust from the muffler back. My 2005 had the original exhaust system on it, and as I was inspecting it I had noticed that two of the three studs in the front flange had broken, so the muffler was only attached with one stud. When I went to loosen the nut on the remaining stud it snapped right off with very little pressure. My muffler was still good, so I drilled out the studs and replaced them with bolts. Man were those studs hard! I went through half a dozen bits drilling them out! In any case, a few weeks later I noticed the muffler developed a crack at the seam, probably from all the jostling, so I ended up getting a replacement Walker stainless steel stock muffler and tailpipe on Amazon. It was $70 for the muffler and $42 for the tailpipe. Rock Auto was cheaper, but after shipping costs were added, Amazon beat their price.(I'm a prime member so free shipping. I love Rock Auto, but sometimes the shipping will kill you.

Anyhow, I thought 16 years was pretty good for the stock exhaust system.

Moral of the story? Buy a new stainless steel muffler, replace the pipes, and you won't have to worry about it. I spent half a day and $30 on drill bits and bolts for a two week fix.
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Re: Exhaust info needed

Postby Wiley [OP] » June 27th 2020, 12:08am

For the flang bolts from the y pipe to each header, what size socket...I assume it is SAE, after spraying with pb plaster two came right off with 15mm but the 3rd was a little difficult so I stopped, as it seems just a touch too large. If it is 15mm and it is just the angle/play, I will use heat next, but the other two were WAY too lose to be honest. edit: 5 off now, 1 to go, looks like 15mm will work

unrelated noob tip-saw a guy use heat, and then drip wax in there to get the studs moving.
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Re: Exhaust info needed

Postby markmitch » June 27th 2020, 12:35am

Never heard of the wax trick but they are actually 9/16 in most cases. But I have seen some with 15 mm nuts too. Glad to hear you got some movement.
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Re: Exhaust info needed

Postby Wiley [OP] » June 27th 2020, 1:13am

Thanks for the tips, got them all. Didn't have a 9/16, but I bet that was the one, 15mm felt a little loose, but who knows, I was lucky they were all in pretty good shape. Now to push my luck with the headers. I love making progress.
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Re: Exhaust info needed

Postby Leeann_93 » June 27th 2020, 2:36am

Mine have all been M10, 15mm head, on my ‘99, ‘00, ‘02 and ‘05. Bought replacements at any LAPS in a pack of 4 (6?) on the Dorman/HELP! carded stuff.

The last time I messed one up, we drilled it out slightly small and tapped it with an M10 to make sure we could replace it with the standard M10 stud. That was on the ‘02.

On the ‘05, the studs that the nuts didn’t zip off, the studs themselves zipped out of the manifold, easily replaced:
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