wrap flex tube for temp repair

[enotslim]

Interesting thread, I will have to do a permanent repair within the next year also. Please post photos and part numbers and suppliers of good flex pipes and the repairs you have done. I'm most nervous about the flange bolts snapping off when I try to remove them.

...
I had the upper flange off a few times when I rebuilt the turbo, it wasn't a problem, the place where you will find rust is the 2 bolt aft cat flange, mine was rotted out,
I cut the 2 bolts off and used a split coupler with 2 new gaskets and high temp (orange) sealant.

https://www.amazon.com/Exhaust-Flange- ... =8-2&th=1

I suspect removing the header/flex/cat will be the biggest challenge to replacing the flex tube on the bench. Tips for removing the two 02 sensors? I've had the same experience at the aft cat flange and used the exact same split clamp. Still a small leak after resurfacing and a new gasket. I probably will replace the flange.

[jonesg]

I suspect removing the header/flex/cat will be the biggest challenge to replacing the flex tube on the bench. Tips for removing the two 02 sensors? I've had the same experience at the aft cat flange and used the exact same split clamp. Still a small leak after resurfacing and a new gasket. I probably will replace the flange.

try double gaskets with high temp sealant on both sides and in between.
clean the mating surface with a sand disk on an angle grinder.
raise the joint level with a jack so it cinches up evenly.

disconnect the 2 sensor plugs , remove o2 sensors after dropping the downpipe.

theres a video showing how to unlock the o2 sensor plugs, its a 1 handed operation with a flat screwdriver blade. edit....found it,

[enotslim]

...
I have a new $44 flex pipe from Advance auto, it has the internal concertina liner which is far better than the $12 versions on Ebay.

Advance and NAPA can get a new downpipe with cat but it costs $900+, come spring I'll weld the new section in,
You'll need to drop the downpipe and make a jig before cutting the old one out to maintain the alignment.

In the photo in the initial post of this thread there is no space between the crosshatched layer covering the actual flex tube and fitting underneath (I think that's how it's structured) on the one hand and the mating surface of the cat on the other. How can a new flex tube be welded in this position (and at the other end of the flex tube that has the same mating surfaces) unless it is a different geometry?

Recommended flex tubes are a different geometry as below. Is that it?

Even so, how do you remove the original flex tube that is welded in place to the cat without cutting and removing the flared end of the cat (and same question at the other end of the flex tube)? Angle grinder to beat the band?

[jonesg]

there is no flare end on the catalytic pipe at either end.
its as you see in the video, the exh pipe slips in or you can butt weld if both are the same.
If you can weld you can make almost any matchup work by making a sleeve.

I spent a lot of time last summer practice welding scrap pipe from a garage dumpster, cut it into sections and weld it back again.
Many times over, , even cut the ears off a flange coupler type and built the ear back with mig and a grinder,
its at the bottom of the photo it works.

[jonesg]

heres my flex, you can cut off as much as you need to shorten it or cut it all off and butt weld.

[jonesg]

a view of the inside, the interlocking plate liner is needed for turbo models to withstand pressure.

[jonesg]

make a jig to align the system before cutting out the old part.

[enotslim]

OP here with new info and plan. I removed the metal mesh that covers the flex tube to discover the tube is fine but had completely separated from the pipe leading to the cat. I wrapped this flex/cat joint and tube/pipewith several partially overlapping layers of aluminum tape, redid the cat/resonator flange joint with two gaskets, red high-temp gasket material and jacks to align the surfaces before securing the bolts, and passed inspection. Even with a faint burning smell presumably (hopefully) from the adhesive on the aluminum tape.

Thanks to jonesg for suggestions on both of these joints. Photos and links to materials are below. Unfortunately, don't have photo of wrapped joint but it's just what it sounds like. Aluminum fitting over the contours of the joint and several inches before and after. Edit - photos of wrapped joint now added taken after ~20 miles of mixed city/highway driving.

Obviously only a temporary fix. Seems that a good shop should be able to weld the flex tube to the cat pipe while everything remains in place in the vehicle. No removal, jig for alignment, soldering on the bench or reassembly required. I can then figure out some type of protective covering similar to the original wire mesh.

The cat flange at the resonator interface is corroded away to the point that it needs repair or replacement to truly seal. (A slight leak currently remains.) This should be an easy job for any shop.

I now have a full year for a permanent fix. I'm considering this opportunity to attempt welding. Pretty sure I can handle the cat flange one way or another. The flex tube/cat joint will require "blind" welding of the portion facing the underside of the vehicle. I bet it's doable by a shop if I fail.

In any case, a much simpler and cheaper solution than I feared.

Now, is there some obvious reason the above plan won't work?

HVAC Tape, Aluminum Tape, 4mil 2 in x 66ft, foil Tape for ductwork, for Metal Repair Insulation Tape, (Silver)
https://a.co/d/gllziyI

FEL-PRO 61451 Exhaust Pipe Gasket
https://a.co/d/fl6m1pc

Permatex 81630 Ultra Red High Temperature Gasket Maker, 3 oz
https://a.co/d/6cQ0Isi

[jonesg]

nice, gives you time to learn how to weld.
I bought a $350 mig and just got a big tank of gas ($365).
Its still cheaper than buying a downpipe system and now I can weld too.

Some use these type of coupler and cut the flange joint off.

https://www.bearriverconverters.store/p ... er-es400ss

[jonesg]

mine just got worse this morning and the real muffler is dragging on the ground, check your rear muffler hanger,
i think that can damage the flex pipe.
Gonna have to fix mine sooner than i wanted, just turned the heater on in the garage.
drat.