Fix leaking exhaust joint
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Thread: Fix leaking exhaust joint

  1. #1
    Registered User cybersaga's Avatar
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    Fix leaking exhaust joint

    So the van had gone over some high snow/ice over this winter and it ended up stressing the exhaust to the point where the joint between the catalytic converter and the pipe going to the muffler seems to have split. All the steel seems like it's still good (although rusted) and I think it's just the top two bolts that were compromised. So I'm hoping to repair that joint without replacing any of the exhaust. But I've never touched the exhaust system before, so I'm hoping to get some direction on if what I think can be done can actually be done.

    In short, I'm hoping to pull those rusted bolts and replace them. Looking at the parts diagram, there is a gasket in that joint. So a couple questions:

    1. Is there anything special about those bolts? Can I just go down to the hardware store and buy bolts?
    2. Is there anything special about that gasket? Do I have to get it from the dealer?


    Clearly, removing those bolts is going to be..... interesting. But there are lots of videos about how to deal with horribly rusted exhaust bolts.

    Fix leaking exhaust joint-20190504_190023.jpg
    Fix leaking exhaust joint-20190504_185350.jpg
    Last edited by cybersaga; 05-05-2019 at 11:27 AM.
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  3. #2
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    I've had to fix this issue multiple times on old aging Honda's, this and the flex pipe are the common failures from what I've seen. Most parts places try and sell a flat gasket but if you search and cross reference on their sites you can find the correct o-ring type gasket. That gasket sits in a groove on one of the pipe ends. Try and get that gasket. As for the bolts, if you want them to be removable in the future then put stainless. If you don't mind possibly having to cut out in the future then get whatever the local hardware store sells. Buy them a bit long and use flat washers on each side to give the old thinned metal some strength help. Also buy some that are thick enough to fit in the hole tightly. Best way to remove the old hardware is a cutoff disk cutting parallel to the flat surfaces. I think I recall one side being a stud so you may need to pound those out being careful not to bend the metal. Lastly, check the other joints as they may be close to failing too. Sometimes it's easier to pull the whole exhaust out after the y-pipe to work on it without being under the car, the way Honda set these up makes it easier than you would think to remove much of it.

    Part interchange search at O'reilly's below.
    https://www.oreillyauto.com/search/c...=18302-SP0-003
    Mike
    07 EX-L RES/NAV

    Sold at 202k miles
    2000 Odyssey LX
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  4. #3
    Registered User cybersaga's Avatar
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    Thanks for your reply. I did so some reading since I posted this. I noticed the gasket is really just a ring. I'll have to get that from the dealer, unless I want to try and get away with reusing the old one.

    And yeah, those are studs in the cat. I just don't know how well a normal bolt will sit. Do you have much experience there? Is there some kind of lip that the studs sit in that a bolt wouldn't sit well on?

    And any idea what size bolts I'd need? I'm guessing M6 or M8.
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  6. #4
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    The O'reilly link I put in above shows some exact cross reference options to the Honda P/N you listed. I've never bothered with metric bolts, just whatever I have in by bucket of bolts. I've done this on maybe 5 or 6 different cars. Some I've gone as far as welding nuts on the flange because there wasn't much metal left. None have leaked after reassembly with some of the vehicles having the repair on both sides of the cat. All you are doing is bolting the flanges back together tightly. I say use bolts that fit well so there is little movement to the alignment when tightening up. I think I recall having to drill the stud side a bit bigger to match the other side on some. As for how they sit, it depends on what is left for metal but because there is 3 the pressure seems to be even as long as you tighten evenly. Taking off the least amount of metal with the cutoff wheel and keeping it straight helps.

    How long the connection lasts depends more on the state of the flange than anything else.
    Mike
    07 EX-L RES/NAV

    Sold at 202k miles
    2000 Odyssey LX
    Trans at 82k -- Tru-cool trans cooler
    DIY Timing Belt at 104k
    Hidden Hitch & Airlift 1000's

  7. #5
    Registered User cybersaga's Avatar
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    I haven't fixed this yet, but I will this weekend (maybe tonight). But the van threw up a P0159 code today (O2 sensor slow response). Does anyone this that could be caused by this leak in the exhaust?

    I'm going to just clear it, fix the leak and see what happens. Just want to know if it makes sense that it could be related.
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  8. #6
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    I would ignore that unless you get it after the leak is fixed.
    Mike
    07 EX-L RES/NAV

    Sold at 202k miles
    2000 Odyssey LX
    Trans at 82k -- Tru-cool trans cooler
    DIY Timing Belt at 104k
    Hidden Hitch & Airlift 1000's

  9. #7
    Registered User cybersaga's Avatar
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    Makes sense. That's what I've done so far.

    I got it done on Saturday. It's been through a full drive cycle and that code hasn't come back (yet).

    I ended up removing the cat entirely. Here's what I did in case it helps someone else:

    1. Unbolt the heat shield around the cat. I only needed to undo the two bolts nearest the ground. The heat shield had rusted through around the back of it, so it wasn't even connected on that side.
    2. There's not enough room to pull out the back half of that heat shield, so I removed the larger heat shield behind that. You may not need to do this if the nuts on the cat are actually usable, but mine weren't, so I needed the space. There are 3 bolts holding that larger heat shield on. Two are easy. One is behind the cat, but I managed to use a 10mm combination wrench to get it out, about 1/8th of a turn at a time.
    3. Now you have better access to the nuts holding the cat on. None of the 6 nuts cooperated. A couple I was fortunate enough to be able to cut just the nut and take it off. On most of them, the nuts were practically indistinguishable from the metal underneath. I had to cut the studs off. I used a Dremel with their reinforced cutoff wheels. Those last so much longer than the cheap, thin brittle cutoff wheels. And I think it was easier to manoeuvre than a grinder.
    4. Once I got it out, I still used my cut-off wheel to clean up the outer rust on the stud side, just so I could see the separation between the stud and the metal around. Then I used a large socket (17mm I think) and put it around the back of the stud. I sat that on top of my table saw (any sturdy surface will do) and hammered on the threaded side with all my might. Eventually, it popped out into the socket.
    5. Once all the studs are out, I used my cutoff wheel some more just to clean up both sides to make sure there's a relatively level area for the new bolts/nuts/washers to sit. You might want to do the same under the van where the cat will go back in.
    6. Install the cat with new bolts (I ended up using 3/8" bolts) with washers on both sides. Feed the bolts through the cat side, so you have more room to get a socket around the nut. Make sure you put anti-seize on those.


    I reused the gaskets, and it seemed to work fine. It's all nice and quiet again. The cat itself looks fairly old and rusted. I wouldn't be surprised if it would need to be replaced - but I don't think that cat is even monitored is it? There are no sensors in it or after it.
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