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Discussion Starter #1
Before I install member KLR3CYL's great looking under belly panel, I was wondering if it was worth trying to patch my very noise catalytic converter with some sort of muffler repair that Advanced Auto sells. My main concerns are 1) would the stuff have any chance of working any better than it does on mufflers, which in my experience is not much (there is one that is sort of a silver liquid that says it hardens to the strength of steel. That might work better), and 2) if the stuff itself or some of the rust fell into the cat, could it cause a code to come up? Even feeling around up there just now might have made some rust fall into. I'll have to see how it acts after I start her up in a little while. The place it's rusting is where down where it connects to the mid pipe (name?) that runs the length of the car to the muffler. In fact, the left bolt is just hanging loose, and the part on the cat itself with the bolt hole has is dangling loose, totally disconnected from the cat itself. The problem is that I can't feel exactly where the hole is or see it in the pics I've taken with my cell phone. One of them is down below.
82407
 

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Why not ask an expert at a muffler shop?

Sam
 

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This looks like the flexible joint at the end of the first catalytic converter. There is a donut gasket inside there which allows the pipes to move relative to each other, and which is probably nearly gone. There should be a bolt and spring on either side which is used to hold the two pipes together, separated by the donut gasket.

I think that if you try to apply any patch material, it will be broken by movement of the two pipes relative to each other and blown out.
 

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Discussion Starter #5
Thanks for the info. I think you're right about the stuff getting blown out. There are two things that came up when I Googled "how to fix catalytic converter with hole it it"--ThermoSteel and QuickSteel, but they probably wouldn't last long. Yeah, I don't know why I wrote bolt when it's obviously a spring. Could that gasket you mentioned be replaced? If yes, 1) could it stop the loud noise by itself, considering the spring is just hanging loose on one side, then there probably isn't any pressure or proper seal on that side, and 2) is it worth the risk because the mechanic may break the other side due to the rust and then there would be no seal.
 

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In reality, I wouldn't even try to "redneck" repair that converter.
A worse case of rust from the salt roads of the NE, I've seen in a while.
You can replace the "doughnut" and it would help. There is supposed to be two bolts and two springs.
 

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The cat is incredibly expensive here in UK new like $1600.

I would def try a redneck repair.

I've thought about basically wrapping it in a full length stainless steel cylindrical cover/sleeve with a new collar/joint on the end to bolt to the downpipe with the doughnut and flexi spring bolts.

The internals are probably OK. Just need a gas tight seal for your sleeve.
 

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Discussion Starter #8
Thanks, guys. I went to the dealer and they said the top cat connects to the bottom cat (the part that I thought was the mid pipe in the exhaust system), and the gasket between them is $31. I would like to try to have the gasket replaced, but I'm too worried that the part with the hole for the bolt on the top cat would break off due to the rust, just as the other side has already happened on the other side, so I'm going to see about having the two cats welded together. I was gonna go to a Monroe Muffler type place, but a guy at Advanced Auto was describing the intricate ways of welding and calling it an art form, so that reminded me of a welding shop my Dad's been going to for 30 years. I'm gonna take it to them on Monday and will let you know what they say.
 

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Discussion Starter #9
I might have accidentally accelerated the rusting because I ripped off the oem splash guard right after I bought the car. It got messed up after I drove it over a parking lot concrete divider, and then my garage made it too hard to remove for oil changes after they jimmied it in place. I rarely drive in snow or on salted roads, but it sits in place for about 9 months every year, so moisture from rain etc. might have gotten inside everything a lot more than if I had had the splash guard in place. That's why I just got Scott's custom made under belly panel. Better late than never : )
 

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It's awesome that you're looking for an economical way to do this and thinking outside the box.

In this case, I would not weld the two halves together. It's a flexible joint for a reason. (You don't want your cylinder head to become the weakest part of the exhaust system!)

From the pictures, you are beyond a standard fix of the flexible joint, because half of it is missing! I recall that the plate is part of the catalytic converter? So your best bet may be to find a muffler place who will cut off the old flexible joint and fabricate a new one, which may or may not be possible for them to do, depending on where you live - emissions testing requirements vary between states.

Also, check RockAuto.com for catalytic converters, because maybe by the time you have paid for the labor, you could have replaced the catalytic converter. However, my understanding is that some of the aftermarket cats are not legal in some states - CA, NY, CT, I think. Someone else chime in?

When you replace the flexible joint, you will want to replace the donut gasket AND the springs and bolts. If the threads are shot on the plate the bolts screw into, drilling them out comes to mind, and may be what some shops do to save time??? Ugh. I don't think drilling out the plates is a good idea. I suspect it might cause an early failure of a different kind, for example, the bolt wearing against the plate as it is constantly being vibrated, wearing thin, and breaking. Thus, I used the method described below to avoid having to re-tap the threads.

You can buy kits with the bolts and springs. If you Google this site (add "site:insightcentral.net" to your search terms on Google) you should be able to find part numbers from people who have done it.

Somebody posted just last week about a suitable, common, very inexpensive replacement for the donut gasket which is quite inexpensive.

Before removing those bolts, I sprayed them every few hours with PB Blaster for three days before trying to remove them. If you crank on them right away you WILL break them off. Instead, alternate slightly tightening, slightly loosening, using the pressure to gently break free the corrosion. Work it very slowly. Eventually it will start loosening. Keep tightening, loosening a little more than you tighten, etc etc. We are talking about fractions of a millimeter - you are LISTENING for movement, not actually seeing it at first. It will take a while to get them going.

Check the rules for your state's emissions inspection to make sure your muffler repairs is going to pass the inspection if it is anything less than replacement with Honda parts.
 

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Also, check RockAuto.com for catalytic converters, because maybe by the time you have paid for the labor, you could have replaced the catalytic converter.
^ This. I was considering straight piping that area with a catalytic delete, but cost with that versus an aftermarket catalytic wasn't much different, so I opted to go the legal route.

Before removing those bolts, I sprayed them every few hours with PB Blaster for three days before trying to remove them. If you crank on them right away you WILL break them off. Instead, alternate slightly tightening, slightly loosening, using the pressure to gently break free the corrosion. Work it very slowly. Eventually it will start loosening. Keep tightening, loosening a little more than you tighten, etc etc. We are talking about fractions of a millimeter - you are LISTENING for movement, not actually seeing it at first. It will take a while to get them going.
+1 on PB Blaster, especially for the O2 sensors. Sprayed them every hour or two over the course of a day and a half (obviously not at night...) and even then they were a pain to come off. But they did, and nothing broke.
 

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Discussion Starter #12
Thanks, guys. I guess I won't try to have the cats welded together. NY has the stricter emissions standards, so even if a welding shop would do the work, it might cause the car to fail inspection. I'm gonna try to go the PB Blaster route, and you gave me a good idea that if I can get the broken plate with the bolt hole off, I could at least try to have that welded back on just by itself. And perhaps just replacing the gasket alone will stop the noise. Will keep you updated.
 

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...even if a welding shop would do the work, it might cause the car to fail inspection...
A quick look at New York's inspection station lookup for, say, Queens county, reveals a lot of auto repair shops.

If any of those do exhaust welding, they may be able to tell you what kinds of repairs are permitted.
 

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Discussion Starter #14
Thanks, sean. So I finally sprayed my rusty bolt on the cat to see if I could loosen it. I wanted to see if PB Blaster works best, and I found this video that tries to test it and some more sprays at
. It claims that Liquid Wrench works best, so I sprayed it about four times on the bolt and nut over an hour, but the bolt won't budge. I'll probably try to tap the socket wrench with a hammer tomorrow, but if that doesn't work, I'll probably leave it alone and then just install Scott's underbelly panel and live with the loud sound coming from the cat, grateful that it isn't making a code come up.
 

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I sprayed it with PB Blaster every few hours for 3 days to ensure it soaked in (did not run the engine). Then I slighty alternated tightening and loosening it to slowly break the rust. Best way to do this? I did it from feel and experience on knowing the feel of the onset of bolt failure (don't ask how I know this!)

How to do this if you don't know the feel of a bolt failing? Maybe try this untested method: Set a torque wrench to, oh, one half the torque rating of the bolt? Then alternately tighten until the wrench clicks, loosen until the wrench clicks, over and over, for maybe 5 minutes. You are breaking up the rust between the threads a little at a time. Then increase to 75% of the torque rating, repeat. Then 100% of torque rating, repeat. About five minutes each. After 100%, increase a few ft-lbs and repeat. If at any time it starts unscrewing on its own, don't get impatient, tighten again, then loosen a little more than you tighten. This breaks up the rust gradually.

It may take a long time, but it's a lot less time than trying to fix the broken off bolt. And if it does break, you won't second guess yourself for having tried your best to prevent that. (Definitely use a new bolt and consider anti-seize.)

Better suggestions are welcome...
 

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OK... I already thought of a better suggestion. If half of the flange that the bolt screws into is missing and you are going to replace it, maybe just busting off the bolt head is more expedient.
 

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An exhaust leak is not something to "live with". Ever hear of Carbon Monoxide?

Sam
 

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Discussion Starter #18
Thanks, sean and Rainsux. I haven't found time yet to continue the work, but I'll try to keep spraying the part with Liquid Wrench to see if it can loosen it up a bit. If it doesn't I'm going to put Scott's underbelly panel on, but now I'm kinda worried that the noise will echo off the panel and become much louder as a result. Will let you know how it works out.
 

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Discussion Starter #19
Bought something called Heat Wrap at Walmart yesterday. Never seen the stuff before. Here's a video that features it:
. Do you think it has any chance of sealing the cat hole? Says it hardens as strong as metal, which means it might keep the cats together should the other side fall apart due to rust but would also make it hard to remove the stuff if any work needs to be done on the two cats. I was going to cut off a small strip and test it on a safe part of a cat or exhaust pipe to see how it looks after hardening. And I would probably use two of them to try to double the strength, though I don't have much hope of it not getting blown out by the pressure and creating a big mess afterwards.
 

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Discussion Starter #20
I think that was the wrong video for this product. I did find a bunch of similar products on Amazon at https://www.amazon.com/s?k=exhaust+heat+wrap&ref=nb_sb_noss_1, with this one being number seven in the list. It gets about 3.5 stars out of 5 with some people saying it didn't work. Other products in the list get much higher ratings, so I might get one of those instead and return this one.
 
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