Rear (downstream) o2 sensor rusted out on the highway - does it need to be replaced?

[JohnOfTheJungle]

As the subject says - I was crushing down the highway and that midpipe between the cat and muffler rusted through, blowing a hole and blowing out the entire flange for the downstream o2 sensor.

I was near a rest stop so I bought an Arizona ice tea, poured it out, cut the can in half and used silicon tape and zip ties to seal up the hole. That held for about 5 minutes before it melted through.

I’m currently sitting about 100 miles from home at a Mavis discount tire in New Paltz, NY. They don’t have a pipe that will work (with flange & o2 connection), but it looks like they may be able to cut a 10” section of exhaust tube lengthwise and hose clamp it on to at least seal up the hole.

The o2 sensor would still be missing though - it’s attached to the wires and resting on top of my rear aftermarket skid.

I think it would be fine to drive home, and I know the downstream sensor is less important, but how urgent is this to fix? Think it’ll cause my engine to start running over rich by thinking it’s too lean?

Since I have to drive home, it should I just unplug the o2 sensor altogether?

I’d prefer not to have to make an urgent fix. If it’s necessary then I’ll see if I can rig up the dummy sensor and just replace that pipe length with a solid pipe since I’ll bet it’ll be cheaper and easier to find.


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[brillo_76]

I would unplug and patch what you have to to get home. Then fix it properly. These flanges rust off and the a/m pipes are junk in the rust belt. I really wish someone made a high end stainless exhaust that never rusted.

OEM is insanely priced and all the 3rd party I seen so far is junk as half the stainless is super low grade and rusts too.



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[JohnOfTheJungle]

Well - the guys at Mavis Discount Tire were awesome.

Despite me getting there an hour before close they cut a spare piece of exhaust tubing in half lengthwise and used that to sleeve the pipe. Then they globbed it up with exhaust putty and used a couple of heavy duty exhaust clamps to hold it on there. They didn’t charge me at all for it - I think they were all enthusiasts themselves (they had a few rat rods in a side garage that they weren’t using to work on customer’s cars). I still gave the guy a $20.

I was able to finish my trip - which was another 40 miles, then another 120 miles back home. Everything is fine for now and no CEL just leaving the o2 sensor plugged in but sitting on top of the skid plate. I guess I’ll search around to see if anyone makes a midpipe, or I can buy an o2 flange and weld myself up one, or just take it to an exhaust shop and see what they can cook up.


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[brillo_76]

Glad you made it home...

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[JohnOfTheJungle]

Glad you made it home...

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Thanks - it definitely scared my fiancé when the 4 inch hole blew out of the side of the exhaust, haha. Scared me too a bit, had me thinking I broke a motor mount or something because of how much it was vibrating, but once I got into the parking lot I was able to diagnose it quickly.

Looks like Rockauto has this piece for a very reasonable $33, I’ll hit it with some high temp bbq or caliper paint to hopefully help it last a little longer. I also bought a new o2 sensor a while back that I’ll go ahead and swap in when I replace this.

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[brillo_76]

Yes I haven't found anything that survives the rust belt... I had an 02 sensor blow out of my 1998 tocuma sr5. Mine was odd as mine blew after I drove somewhere and the exhaust cooled down. I was in the city and thought someone stole my O2 sensors. When I got home I found out it just blew out and I put it back together.


Rock Auto is a good source for A/M parts.

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[JohnOfTheJungle]

I installed that midpipe today. It took me several hours - the main reason is because when installed this Gibson catback system it uses clamps to crimp onto the exhaust pipe.

Well, I when I was installing it I had a hard time getting a tight fit so I really cranked those clamps down. It turns out they’re a real pain when it comes time to get the pipe out.

This mangled rusty piece that I finally pulled out is what was left of the midpipe after I cut it to pieces with my Milwaukee hackzall

You can see how much I had crimped the pipe for the silencer on my initial install of the Gibson system last year

I also picked up a tailpipe expander from HF anticipating this so I could fit the new pipe in there

And here it is installed - I painted it with high heat rust resistant spray paint. It will probably do nothing to prevent rust, but it worth a shot

Bonus pic of the patch job on the old pipe that Mavis Discount Tire did for me last weekend

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[brillo_76]

I was wondering how your were making out. Yes that paint is absolutely worthless on exhaust.

That patched worked and got you home and that's want counts.

One of the reasons I wont use the Gibson exhaust is no flanges. You can see what a pita it is to pull pipes apart that are u bolted together.

Plus it can restrict your exhaust flow which isnt horrible in a 4 runner but something I try not to do.

Thanks for the update. Glad you got the rig back together.

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[drey6]

I will say I’m a fan of the Gibson set up as I’ve been running mine for a few months. I’m in Columbus, Ohio and fortunately my exhaust upstream from the muffler has somehow survived well for my 1996 4R.

I clamped as the OP did but after a week drove it to my muffler shop in the hood and they welded in stainless in front of the Gibson muffler since the clamp wasn’t sealing the previous pipe perfectly and it also bent it quite a bit... (as your photos also show how much the clamp can damage the existing pipe). The shop welded the muffler and welded the seams at the muffler/elbow/tailpipe too. I realize this doesn’t make it removable but everything in front of the cat and the cat itself is so I’m fine with that. If it needs repaired down the road I’ll take it to the shop but Gibson’s lifetime warranty is something that I hope translates to a true lifetime of use. The exhaust for my DD won’t see much abuse and I don’t see any major needs for it to be removed to access other repairs so I’d rather have it sealed by a weld than clamped. I think the SS pipe + welds had me all in $65 cash out the door. Something to consider if your a little OCD like me.

 

[JohnOfTheJungle]

I will say I’m a fan of the Gibson set up as I’ve been running mine for a few months. I’m in Columbus, Ohio and fortunately my exhaust upstream from the muffler has somehow survived well for my 1996 4R.

I clamped as the OP did but after a week drove it to my muffler shop in the hood and they welded in stainless in front of the Gibson muffler since the clamp wasn’t sealing the previous pipe perfectly and it also bent it quite a bit... (as your photos also show how much the clamp can damage the existing pipe). The shop welded the muffler and welded the seams at the muffler/elbow/tailpipe too. I realize this doesn’t make it removable but everything in front of the cat and the cat itself is so I’m fine with that. If it needs repaired down the road I’ll take it to the shop but Gibson’s lifetime warranty is something that I hope translates to a true lifetime of use. The exhaust for my DD won’t see much abuse and I don’t see any major needs for it to be removed to access other repairs so I’d rather have it sealed by a weld than clamped. I think the SS pipe + welds had me all in $65 cash out the door. Something to consider if your a little OCD like me.

Exhaust looks fresh, I like it! I also have been unable to get it to seal perfectly going into the muffler. When I start the Runner I’ll see water coming out of there so I know it’s not perfectly sealed. That’s part of the reason why I had clamped it down so hard previously.

Anyone have an opinion on whether a little leak here and there around the muffler affects performance? The sound is good, so if performance is negligible then I’ll stick with it not welded.

I will say I am definitely going to need to remove the end piece at the tail pipe when I go to mount a new bumper because it’s perfectly lined up with those bolt heads. So for that reason alone I wouldn’t weld the back half after the muffler.



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[brillo_76]

I will say I’m a fan of the Gibson set up as I’ve been running mine for a few months. I’m in Columbus, Ohio and fortunately my exhaust upstream from the muffler has somehow survived well for my 1996 4R.

I clamped as the OP did but after a week drove it to my muffler shop in the hood and they welded in stainless in front of the Gibson muffler since the clamp wasn’t sealing the previous pipe perfectly and it also bent it quite a bit... (as your photos also show how much the clamp can damage the existing pipe). The shop welded the muffler and welded the seams at the muffler/elbow/tailpipe too. I realize this doesn’t make it removable but everything in front of the cat and the cat itself is so I’m fine with that. If it needs repaired down the road I’ll take it to the shop but Gibson’s lifetime warranty is something that I hope translates to a true lifetime of use. The exhaust for my DD won’t see much abuse and I don’t see any major needs for it to be removed to access other repairs so I’d rather have it sealed by a weld than clamped. I think the SS pipe + welds had me all in $65 cash out the door. Something to consider if your a little OCD like me.

Glad it works for you. I just like to be able to take things apart. Being welded without any flanges will make that difficult as it will have to be cut apart to be removed them welded back together.

The reason your front pipe is still together is that Toyota used some kind of semi stainless for those pipes and they normally do not rot out. From the cats back is a completely different story.

This may have changed in the later years with the daul cats. All my 97 and 98s with single cats are still intact.

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[drey6]

Glad it works for you. I just like to be able to take things apart. Being welded without any flanges will make that difficult as it will have to be cut apart to be removed them welded back together.

The reason your front pipe is still together is that Toyota used some kind of semi stainless for those pipes and they normally do not rot out. From the cats back is a completely different story.

This may have changed in the later years with the daul cats. All my 97 and 98s with single cats are still intact.

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Sorry, just now seeing this. New to the site and I
need to set up notifications. Good info on the type of metal used for the exhaust in front of the cat. I too like to take things apart if needed but as far as I can tell, loosening the hangers will give me enough play to get to most everything in the area with ease. The cat is still mounted with flanges on both sides so if that needs replaced down the road I’ll be in good shape. Next up is to wire wheel off undercarriage rust, get some phosphoric acid etch goin and use my KBS undercoating kit to get it looking mint down there. It’s always gonna be an on road DD but boy would I love to see 300k and beyond!

 

[brillo_76]

Sorry, just now seeing this. New to the site and I

need to set up notifications. Good info on the type of metal used for the exhaust in front of the cat. I too like to take things apart if needed but as far as I can tell, loosening the hangers will give me enough play to get to most everything in the area with ease. The cat is still mounted with flanges on both sides so if that needs replaced down the road I’ll be in good shape. Next up is to wire wheel off undercarriage rust, get some phosphoric acid etch goin and use my KBS undercoating kit to get it looking mint down there. It’s always gonna be an on road DD but boy would I love to see 300k and beyond!

Oh it's ok. :] Everyone is busy I just try to help

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