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Catalytic converter, exhaust leak, rust. Need advice....

11K views 23 replies 8 participants last post by  wwdwgs  
#1 · (Edited)
Well.... Finally (not that I wanted it and expected it... eagerly) my car developed an exhaust leak. It seems to come from the very rear of cat converter. I'm not sure where - either from two mating flanges (there's a gap) or from a rusted weld between cat and it's rear flange.
The bolts that hold two flanges are rusted - they did a great job (rusting).
When It will get cooler, I'll run engine again and try to feel the leak by hand.
1 - if it's gap between the flanges (the bolt don't hold them together), what are the "easy" options/methods to extract all 3 bolts, clean flanges' surfaces and assemble them back? Mind that car will be on jack stands...I've no pneumatic tools at all, nor real power tools like hammer drill/chisel...
2 - if there's an additional crack at cat and flange, could that be welded? with arc or mig welder?
3 - bolts and nuts. Is there a good source of them in stainless steel flavor?
Here are some preliminary pictures...:
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BTW, I'm not a welder...

EDIT:
there are the bolts that hold cat..:
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#2 on diagram:
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Looks like I'll have to remove car with pipe and see how easy it'll be to remove those bolts.... I don't see any way to remove these bolts when pipes are installed.
 
#2 ·
Mine looks exactly like yours, well mine are worse as it’s a 2000.
I’ll probably just order the FX 8043 and either take the 2 Kits to a muffler shop or a welder.
I can weld, but this may be to thin to weld on for my liking..
Your part number may be different as this is for a 1999-2004
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#6 ·
Rather than feeling for the leak by hand, try using the soapy water trick. Get some soapy water in a spray bottle and spray it on any suspect points. It will bubble where there is a leak.


 
owns 2006 Honda Odyssey EX
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#12 ·
I just went through this myself. Exhaust was leaking at the gasket because the nuts had rusted away. Used a grinder to grind the nuts off and a few good wacks with the hammer got the converter off. Then used a punch and hammered the studs out of the catalytic converter. Got new gaskets and just got some grade 8 bolts and nuts that fit in the holes. Did have to grind at the flange so the head of the bolts would sit flush against the flange.
 
#18 · (Edited)
Update:
Finally, I had time to inspect the flange joint between the catalytic and pipe.
Looks like the flanges are warped (at top).
Video: Exhaust leak
Instead of welding, I'm thinking about cutting off all rusted studs and nuts, trying to clean flanges' mating surfaces and installing two 3-bolt split flanges (with s/s nuts/bolts). Probably 2 1/2" dia. as depicted below:

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I know that this flange will rust... oh, well.
If I wont be able to remove pressed-in studs (on cat's flange), I'll grind them flush.
As of s/s hardware, I'll use 316 s/s bolts/nuts/washers. I hope that this 316 s/s will be strong. Another option is to use Bumax s/s (strong as a steel counterparts, but expensive - $4-5 apiece).

Thoughts. I don't know how soft the exhaust flange steel is. Is it possible that the upper parts of the flanges were bent when I raised the engine to fix head gasket? Raised by about 2".
 
#19 · (Edited)
another update/thoughts:
I'm looking at the parts - the gasket that goes between flanges in question is thin round one (number 1):
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I started to doubt that mating surfaces will be perfect (rather in acceptable shape).
As of now, I can't remove the J-shaped pipe with cat (called converter part #1) because of extremely hard-to-reach one bolt of 2-bolt flange (beginning of pipe).
One way to deal with it, and it's not my favorite way and it's still too tight to get to one bolt, is to cut spring-loaded bolts.
...
Edit:
after some search, some sources show gasket to be like this:
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Hondapartsnow, shows a thin one, RA - a triangular-shaped... (years 2010-2011). go figure!
 
#20 ·
That split flange looks interesting. Hopefully it will work. I have cut my own exhaust gaskets when I have no other choice. In the video below they show cutting the material with tin snips. A cutoff wheel on an angle grinder also works. To make the bolt holes the the hole punch works the best. I would have this material on hand when doing the work in case the Honda o-ring gasket looks like it won't seal. Or you end up using 2 split flanges.
Why do you say (and show a pic of) a J-pipe? Is your Ody a 4 cylinder? My Ody has a Y pipe for the V6.

 
#22 ·
update: (finally).
I inspected the rest of the exhaust - the other flexible (donut) joint between pipe with resonator (#8 on diagram above) and a muffler (or should I say "silencer" with an britt accent?) (#15) rusted and was free-handing, rubbing a half-axle.
That loose connection would put extra pressure on cat./pipe joint and helped to bend the flanges.
condition after some prep work:

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on the picture below (cat. flange view) I goofed and cut-off too much of flange "ear" exposing gasket's groove. Oh, well....:

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The picture below shows a rear flex joint. Note that hook rusted and came off from it's proper place on the pipe. I already fixed this joint, but with cheap flange a few years ago... 3 or 4.... Note rubbing on half-axle. BTW, that axle is also 3-4 years old.... I think it was designer to collect the rust. Left pipe is with the resonator, right - with the muffler.

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Painted flanges and hardware....:

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This is how cat/pipe joint looks like. I know it's a rather temporary measure and I will have to replace the whole exhaust "system" later, in better future. 3/8x16 2" long bolts are barely enough... better to use 2 1/4" (stainless steel).

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I don't know how long it will last....2-3 year is enough for me....
Result - exhaust works fine: no noise.

BTW, I couldn't get to one nut on front flex joint (in front of O2 sensor - that with green wire), therefore, I had to fix the way I did.

Lesson - measure before cutting.... don't eyeball it.
That was for 4-cyl CR-V.
 
#24 ·
This was my "plan A", I always knew, that, if I'll screw up, I can use "plan Z" - replacing the exhaust system.
A therapy through mechanics. A mechanical therapy?