Broken exhaust flex pipe, exhaust removal

[JonnyNof]

The flex pipe on the exhaust came undone on the inside, braided sheath is still intact, but definitely blowing exhaust out in there, loud as hell, and the motor stumbles I wager since the rear sensor is not getting the readings it expects.

I'm going to weld a new one in, my question regarding removing the exhaust. I saw there are bolts after the header, and a sort of collar fitting just aft of the catalytic converter. Can I undo the fittings at those two sections and pull the middle section out, or does the hind end of it need to come down as well. I'm just not certain how that joint behind the cat works.

Also while I'm in there should I look at redoing the cat, I don't know if it had ever been replaced, 215,000 miles on it now, and it was driving just fine with what was in there. I just don't want to weld a new flex joint in to have to replace the cat in another 25k. My other vehicles with this many miles on them don't have converters so I'm just not sure what lifespan we're seeing out of them on the vans.

Thanks!

[Burntboot]

Everything should just unbolt, though penetrant and sometimes even the blue flame adjustable, will be required.
Looks like standard gaskets fr and rear and as that pipe is part of the cat section, as long as the cat is good all should be fine.

Cat's fail when they get contaminated or they rust out. If contaminated, you will see when you look into the input side.
Should be a lovely honeycomb thing going on and you should be able to see defuse light thru it (strong flashlight required).
If it looks like something is melted onto it, thats contaminated and time for replacement.

Rock auto does have a variety of pipes in stock at ridiculously cheap prices, if you wanted the easy way out.
Maybe even just looking at the pictures would help you see what you're extracting and the gaskets/hardware required?

An aftermarket Cat won't have the lifespan of factory but seeing as those A/M pipes are missing a zero (compared to factory pricing) its probably not an issue.
BB

[JonnyNof]

Thanks man, yeah it was shortly after I was looking at flex pipe that I saw there's still an aftermarket for that whole setup. Hell even a Magnaflow version, which struck me as humorous. I may opt to just replace the entire part as is and save myself the time of lining things up, cutting out the old flex, making sure things are still aligned and welding in a new one. That and my garage being a wreck right now makes getting to the mig a bit of a pain. Gonna pick up some penetrating spray and give it a couple days soak til I can get at this come Sunday. Either way, appreciate the info.

[JonnyNof]

Yep, got it apart, fortunately nothing needed the torch just a couple ugga duggas following the application of deep creep. Only irritating part was the replacement didn't have studs for the forward hanger, so I had to pick up some bolts. All is good now though. I took some video we'll see how it turned out, if anything is usable I'll pop it up on the tube.

[laggle]

Hey Jonny,

I just found out that I need a new catalytic converter on my 95 Previa S/C AWD with 255K miles. The local shop said that it would be over $1K to do the replacement. It looks like aftermarket converters are on rockauto for around/less than $300. How difficult is the replacement for an amateur to do on his own? Did you ever post that youtube video of the job? Was there a brand of replacement cat you bought?

Thanks!
Dave

[Jonny]

Sometimes if you live where there are winters with salted roads and your exhaust system has not been touched in years, you end up with rusted "lumps" rather than bolts or nuts. No alternative at that point to grinding the bolt heads off then drilling and/or tapping.

This is the joint behind the catalytic converter, ground flush, through-drilled, with stainless bolt and nut replacement. It's about 5 years old and still rust free...
Sorry about the blur.

DSCN5029.jpg

This is the job from today on the joint just forward of the flex pipe. They are the bracket bolts rather than the actual exhaust stud nuts. I wish I had taken before photos - one bolt was still barely recognizable as a bolt, the other was a definite lump. I just drilled and tapped a smaller hole through the ground-off bolt and put 6mm stainless ones in there (because I already had them) ... the oem are 8mm, so I hope they're strong enough. I'll report if my pipe falls off.

DSCN5031.jpg

Somewhere on here Tim has a post on how to expertly drill out a bolt (I'll try to find it and link to it) edit here it is... https://www.toyotavantech.com/forum/...=drill+bushing
but for something not critical like this, a careful eyeballing, a good sharp center punch and some sharp hard drill bits usually suffice. Drill a small pilot hole first - it's easier to get a small bit to go where you want it. Get yourself a good set of left-handed bits too - sometimes if you go with the bolt tap size LH bit and have it pretty well centered it will spin what's left of the old bolt out of the hole when all else has failed. And those tapered spiral thingys which they sell as broken bolt removers - all I've found they are good for is themselves breaking off inside the bolt about 50% of the time and making the job a lot harder. Maybe there is a good brand of these out there somewhere? Anyone? Edit: I see Tim has a recommendation in his post.

[eastman51]

Thought I might tack onto this since I just replaced my whole exhaust last year.

My van had a horrid exhaust on it, the flex pipe was severed off at the front from rust and age; the cat was replaced with a Cherry Bomb, there was a gigantic muffler on the back. And top it all off, the entire thing was held up with chicken wire. It looked horrible, it sounded horrible, and rattled like crazy. Oh yea, and both O2 sensors were broken.

I purchased the RockAuto catalytic converter, new O2 sensors, and a RockAuto muffler; as well as parts store hangers for the front and brand new Toyota ones for the muffler as they are special.

I cut the old exhaust in sections to remove it because it was all one piece. For the front piece, only one nut came off it's stud, the other two snapped clean off as expected. I drilled through them and just used small diameter bolts to fit through my holes. Admittedly I could have done the drilling better because it took a very long time and ate through a good chunk of my Milwaukee drill bit.

The RockAuto cat bolted up great with a pair of new gaskets from the local parts store and both O2 sensors fit and worked great. Unfortunately, the RockAuto muffler wasn't long enough. The flange of the muffler didn't reach the back of the new cat, so I ran the van without the muffler until I could find time to meet up with one of my buddies to get it on a lift and have him weld an extension to the muffler.
With the extension, the muffler bolted up perfect and there's no leaks at all. It's quieter than it was, and sounds decent albeit very raspy.

I'm having trouble uploading pictures, so I will edit this later.