Exhaust leak between the cats

[C6H12O6]

I've read a bunch of the archived threads, but not all. Most seem to be griping about the price or leaks before or after. I have a pretty sizeable leak right smack in the middle of the two cats on my '95.

I started the rig up yesterday morning standing outside of the PS door (don't ask) and was hit in the shins with a huge plume of steamy exhaust. I was hoping it would seal itself off once the cats warmed up, but no dice. I guess that's what caused the 420 MIL code a couple weeks ago. I reset the light pulling the EFI fuse and it hasn't come back, but a leak that big can't be a good thing.

Anybody here have any experience just pulling the cats, cleaning the flanges up and replacing the gasket? I'm hoping that's all it is. OEM cats are $$$. I'm also hoping that this leak might be the cause of my truck not having the power it did even just a few months ago. I noticed the lack of power right after I banged my exhaust on a rock (smashed a small dent into the hangy-down part in the tube just aft of the cats). I bet the jolt broke the gasket loose a little.

 

[OGBeno]

The 2 14mm bolts holding the cats together at the flanges are usually really rusted out and corroded or plain rusted to the flanges (ask me how I know.... ).

I took the two bolts out (er...hacked them off flush to the flange then drilled through). There is a small circular metal gasket that goes between them.

Get two new bolts/nuts, put them through and then drop a weld along the flange meeting points for extra strength.

Cheers.
-onur

 

[Rich]

...I'm also hoping that this leak might be the cause of my truck not having the power it did even just a few months ago. I noticed the lack of power right after I banged my exhaust on a rock (smashed a small dent into the hangy-down part in the tube just aft of the cats). I bet the jolt broke the gasket loose a little.

Could be that the hit on the exhaust broke up the comb in the converter and you may now have an obstructed exhaust, which in itself could have conributed to the gasket blowing out.

With a rubber mallet you can lightly rap on the rear converter and listen for bits rattling around that shouldn't. Don't hit it too hard; don't want to create more damage.

 

[C6H12O6]

Yeah, that's possible I suppose. I hope not ~ I like a $5 gasket a lot better than a $1K cat.

 

[concretejungle]

Here you go:

https://forum.ih8mud.com/showthread.php?t=40864&page=2&highlight=exhaust

 

[alvarorb]

Steve,

At the end of every wheeling season I change the seal between the cats. It's pretty normal that smacking the cats against a rock will cause it fail.
The original seal is about $10 from Toyota, and aftermarket one is about $5.

If the seal is gone, probably your exhaust system mounts might be damaged as well. I'd suggest you take your rig to a local muffler shop and have them take a look at it. Exhaust work is not expensive at all.

Regards

Alvaro

 

[C6H12O6]

I'm guessing it's a good idea to replace all three seals at the same time? Or should I leave the ones that aren't leaking alone?

I'll be calling CDan this afternoon. Thanks for the help. Hopefully this will bring a little power back and help with my nearly instant decrease in mileage. I went from 14.5 mpg in mixed driving nearly every tank to 12.5 overnight. I attributed some of that to the winter blend/ethanol gas, and it has gone up to 13.6 on the first tank of non-ethanol gas last week, but that certainly isn't a good average. We'll see.

Thanks again,
Steve

 

[CreeperSleeper]

Wow Steve, you are getting anal!

I fired my 80 up last week and was proud to see exhaust leaking from in front, between and behind my cats... it also looked like it was leaking from the 2nd cat, but I couldn't really tell with all the other leaks.

Oh well, I don't have a code adn have plenty of power so I'm not too worried about it!

 

[C6H12O6]

I'm not anal; I'm just... well, ok. I'm anal.

What's the old saying about wanting a lady that's sweet in public but a freak in the bed?

I've always been into having things as close to 100% as possible mechanically speaking. That way I don't worry about driving them hard when I'm playing. My old muscle car was the same way. Everything was dialed in and in tip top shape. People always commented when I popped the hood at how pampered it looked, but then I would drive it like the FBI was after me everywhere I went.

Plus, I hate the feeling of f-ing up a $1K part and learning afterwards that I could have more or less prevented it with a $5 gasket, or oil changes, or a new hose, or stupid constant tension clamps, or fresh belts, or decent filter, or ridiculously expensive red coolant, or factory original parts, or...

Hell, if we weren't all a little obsessive about our vehicles we'd drive j33ps or bland rovers.

PS ~ Chad, I'm still waiting for the pictures from our little outing. As soon as I get the DVD with the images, I'll post them up on my website so you can take a look. The story is coming along nicely. You'll dig it.

 

[Stumpalama]

I am dealing with your very problem right now. It seems the PO banged the cat (Should have noticed from the dent in the running board [now off]) which also destroyed the rear mounting bracket. Anyway, I removed the bracket and cut a 1" by 11" piece of 16ga sheet metal and bolted it to the mounting point and bent it down and around the pipe and tack welded it to the pipe (so if the weld breaks at least it's still held in place until I can re-weld it).
- OK, so I replaced the gaskets, but noticed alot of metal loss between the flanges (possibly from long time exhaust leak?). After putting it all back together, it was still leaking (5 minutes ago ). Also used stainless steel bolts to save grinding in the future.
- SO, my solution is to remove the cat again and grind down the mating surfaces so the gasket will be crushed (not too hard I hope) and do its job. Funny, I have a 25yr old FJ40 that had less wear around the cat than my 97 LX450.
Pictures follow:
Cat with gap (shiny bit is gasket)
View attachment 64368

Exaust hanger