Cat replacement hell

[Nelsonmd]

Just thought I'd share some pics of my sucky weekend of trying to replace the CAT's and having to deal with disgusting amounts or rust...

Rear flange joint


Flange joint between the 2 cat's. I tried to stop the leak here by welding it, but it was in vain and I never got it sealed completely.


Cat to Crossover joint before


Rear O2 sensor. 1 stud is missing because it was too corroded to put back in when I replaced the O2 sensor. I replaced it with a grade 10 bolt, which didn't resist rust very much at all.


Front A/F sensor:


While the 3 studs/nuts on the CAT to Crossover don't look that bad, they were. 1 nut came off with alot of torque, 1 stud snapped off, and the third nut rounded off. I pre-treated with heat and PB blaster to no avail. I had to cut off the rounded nut, so I had basically 2 broken off studs. I first thought I might be able to drill them out, but those studs appear to be hardened or something, because my bits got nowhere. I pulled out my small Oxy/MAPP torch and heated up the one stud til it was cherry red and tried to use vise grips, but the vise grips just stripped it and slipped off.

So I was left with no good ideas, so I went to a mediocre one and cut slots in the flange so I could pound the studs out. I used my dremel to cut the slots from the wheel well, and managed to pound the studs out.

First one finally pounded loose


For the back one, I used my dremel with the engraving extension thing so it could sneak back there. It was harder to pound out, so I had to make a tool to pound it out. I cut an angle on a piece of steel strip I had lying around so I could wedge it in and pound with a hammer


It took a surprising amount of pounding to get it to break loose, so those studs were REALLY corroded in there. Anyway, I finally got them out, and got the new front CAT up there just hand tight using 2 M8 bolts and flange washers. The M8's are smaller than the M10 studs there originally, but I think they should be ok. The stud that is still there and in tact I will use again, but I am having trouble matching the threads, they look like M10 1.25, but I got one of those nuts and it didn't go on, so they may be M10 1.00. Here is what it looked like in the end.


Anyway, I ended the night when I realized that the bolts/studs on the muffler flange or so corroded they are immovable (again tried the torch and PB blaster, vise grips, etc.) I am concerned that the muffler flange was threaded, so I can't just cut the bolt off and pound it. I figure I will cut them off tomorrow night and if they don't pound out, I'll cut slots on the muffler flange just like the crossover flange and pop them out that way. Once that is done, I should be able to just pop the new ones on, install the O2's, and I'll be good to go.

Now if I can ***** a little...
1. Whoever thought it was a good idea to put threaded studs directly into exhaust flanges is a complete twat. They corrode immediately and you can't cut them off. This would have been easy if they were through holes with bolt and nut.
2. While cutting off the rounded nut, my cutting wheel slipped and cut into the tranny dipstick tube, so now I need to replace that too... See the second to last pic.
3. The leaky flange was nearly completely rusted through. The flange part. That is about 3/8" thick. Somethings tells me that even on an exhaust you shouldn't be able to rust through 3/8" of steel in 10 years.
4. I hate rust. Though I vowed to never forget how much I hated rust, I got optimistic when I saw that the crossover studs weren't completely rusted away, but shame on me for being so foolish. Rust sucks. Don't ever forget that. Don't buy a 4runner if it has rust on it.

 

[Doc2012]

bit the bullet and get some headers while you're at it. LOL.

 

[BillIam]

i had this same leak, took it to my local muffler shop andhad them cut it out an replace it with pipe. cost me 40$ and never leaked again!

 

[DeathCougar]

Now if I can ***** a little...
1. Whoever thought it was a good idea to put threaded studs directly into exhaust flanges is a complete twat. They corrode immediately and you can't cut them off. This would have been easy if they were through holes with bolt and nut.
2. While cutting off the rounded nut, my cutting wheel slipped and cut into the tranny dipstick tube, so now I need to replace that too... See the second to last pic.
3. The leaky flange was nearly completely rusted through. The flange part. That is about 3/8" thick. Somethings tells me that even on an exhaust you shouldn't be able to rust through 3/8" of steel in 10 years.
4. I hate rust. Though I vowed to never forget how much I hated rust, I got optimistic when I saw that the crossover studs weren't completely rusted away, but shame on me for being so foolish. Rust sucks. Don't ever forget that. Don't buy a 4runner if it has rust on it.

The studs are a great idea if you don't live in an area where they salt the roads. I will never ever ever in my life move to an area where they salt the roads. Not even for eleventy billion dollars.

I really don't know how you east coast guys do it. Having to replace parts not because its reached the end of its life, but because the rust has become so bad its ruined everything underneath. Seems like stuff just gets cobbled together over there until it completely falls apart or won't pass inspection (not sure how that works, we don't have inspections here)

 

[fish0281]

The studs are a great idea if you don't live in an area where they salt the roads. I will never ever ever in my life move to an area where they salt the roads. Not even for eleventy billion dollars.

I really don't know how you east coast guys do it. Having to replace parts not because its reached the end of its life, but because the rust has become so bad its ruined everything underneath. Seems like stuff just gets cobbled together over there until it completely falls apart or won't pass inspection (not sure how that works, we don't have inspections here)

Mine spent its life on the salt-free roads of Oregon and it still had rust on the exhaust flanges. Those things spend their life getting hot/cold, which is an amazing corrosion (or even just metal-metal diffusion bonding) enabler. Exhaust work is a biatch and I hate it. Crap is expensive too. /rant.

 

[doubleA]

My cat looks the same... a rust haven of hell. The support bracket off my cat broke about 2 years ago.

Currently I am replacing the rear bumper section. Almost every bolt snapped off, or were so rounded I could do nothing except cut/drill.

In the end I ran out of time, I took it to a shop. The labor was <100 to finish it up. Oh well, rust wins again.

My first round was my rear axle housing, replaced that one year ago.

I am thinking to sell my 4runner next summer... the rust thing has gotten old after only a few fixes...

 

[downpour11]

That sucks!

Rust.... turning the easiest of fixes into an absolute nightmare.

 

[nissanh]

I used to wash the under body on every weekend while I lived in Reno/Tahoe. Managed to keep it rust free through those years. I also apply WD-40 before any winter.

 

[Nelsonmd]

Well, I got this crappy project finished tonight. No pictures, I forgot to take any, but I was able to use a c-clamp and socket to press out the remaining 2 bolts on the muffler flange, but they were pretty tough to get out.

One little point I noticed was that the gaskets seemed a bit off. 1 cat came with one small and one large gasket, and the other came with 2 small cat's. The large one had to be used on the joint between the front cat and the crossover, and the small ones went between the cats and between the rear cat and muffler. In the muffler joint though, the muffler side looked like it matched up to the larger size like was used on the crossover joint (the pipe is larger and the countersink on the flange was larger), but the cat side definitely used the smaller gasket (the gasket fit snug over the pipe). It looked like the gasket did contact the inner corner of the muffler pipe, but it didn't quite look the same as the other joints.

Anyway, I started her up and it was quieter than it has ever been, and I will see if I get rid of the stupid P0420 code once I drive it a bit more. It appears successful so far.

 

[Nelsonmd]

Quick updated since I revisited this thread:

The Eastern catalytic cats have been perfect so far, the CEL has been off since installing them and hasn't come back on. I'm very pleased so far.

 

[tee-bone]

Thanks for the update.

I get the P0420 code every once in a while too - figure I will just try to wait until someone steals my cats until I replace them, since I am still able to pass smog at this point.

When I do, I'll try the same cats as you - but regardless if I am replacing them due to theft or lack of function, I'll let someone at a muffler shop do the work, since they salt the roads in UT.

 

[Nelsonmd]

Thanks for the update.

I get the P0420 code every once in a while too - figure I will just try to wait until someone steals my cats until I replace them, since I am still able to pass smog at this point.

When I do, I'll try the same cats as you - but regardless if I am replacing them due to theft or lack of function, I'll let someone at a muffler shop do the work, since they salt the roads in UT.

Utah salts? I would have thought that like CO, they would use Mag chloride instead to preserve their soil quality.

Definitely run them til you are forced to change them to pass inspection. I'd even try the guaranteed to pass stuff to get you by. I went as long as I possibly could, even going to a place a knew would pass me even with some incomplete tests.

 

[Ghostrider]

Just thought I'd share some pics of my sucky weekend of trying to replace the CAT's and having to deal with disgusting amounts or rust...

Rear flange joint


Flange joint between the 2 cat's. I tried to stop the leak here by welding it, but it was in vain and I never got it sealed completely.


Cat to Crossover joint before


Rear O2 sensor. 1 stud is missing because it was too corroded to put back in when I replaced the O2 sensor. I replaced it with a grade 10 bolt, which didn't resist rust very much at all.


Front A/F sensor:


While the 3 studs/nuts on the CAT to Crossover don't look that bad, they were. 1 nut came off with alot of torque, 1 stud snapped off, and the third nut rounded off. I pre-treated with heat and PB blaster to no avail. I had to cut off the rounded nut, so I had basically 2 broken off studs. I first thought I might be able to drill them out, but those studs appear to be hardened or something, because my bits got nowhere. I pulled out my small Oxy/MAPP torch and heated up the one stud til it was cherry red and tried to use vise grips, but the vise grips just stripped it and slipped off.

So I was left with no good ideas, so I went to a mediocre one and cut slots in the flange so I could pound the studs out. I used my dremel to cut the slots from the wheel well, and managed to pound the studs out.

First one finally pounded loose


For the back one, I used my dremel with the engraving extension thing so it could sneak back there. It was harder to pound out, so I had to make a tool to pound it out. I cut an angle on a piece of steel strip I had lying around so I could wedge it in and pound with a hammer


It took a surprising amount of pounding to get it to break loose, so those studs were REALLY corroded in there. Anyway, I finally got them out, and got the new front CAT up there just hand tight using 2 M8 bolts and flange washers. The M8's are smaller than the M10 studs there originally, but I think they should be ok. The stud that is still there and in tact I will use again, but I am having trouble matching the threads, they look like M10 1.25, but I got one of those nuts and it didn't go on, so they may be M10 1.00. Here is what it looked like in the end.


Anyway, I ended the night when I realized that the bolts/studs on the muffler flange or so corroded they are immovable (again tried the torch and PB blaster, vise grips, etc.) I am concerned that the muffler flange was threaded, so I can't just cut the bolt off and pound it. I figure I will cut them off tomorrow night and if they don't pound out, I'll cut slots on the muffler flange just like the crossover flange and pop them out that way. Once that is done, I should be able to just pop the new ones on, install the O2's, and I'll be good to go.

Now if I can ***** a little...
1. Whoever thought it was a good idea to put threaded studs directly into exhaust flanges is a complete twat. They corrode immediately and you can't cut them off. This would have been easy if they were through holes with bolt and nut.
2. While cutting off the rounded nut, my cutting wheel slipped and cut into the tranny dipstick tube, so now I need to replace that too... See the second to last pic.
3. The leaky flange was nearly completely rusted through. The flange part. That is about 3/8" thick. Somethings tells me that even on an exhaust you shouldn't be able to rust through 3/8" of steel in 10 years.
4. I hate rust. Though I vowed to never forget how much I hated rust, I got optimistic when I saw that the crossover studs weren't completely rusted away, but shame on me for being so foolish. Rust sucks. Don't ever forget that. Don't buy a 4runner if it has rust on it.

It's not just rust but - as you pointed out - bad design choices for future work. I've said it before but every design engineer should be forced to actually work on their design afterwards. Things like those bolts or the rear shock design are perfect examples of a nightmare to work on after the fact.