2004 XC70 leaks at the cat converter

[enotslim]

2004 XC70, 120k miles, with one or more small leaks in the exhaust flex pipe, possibly more leaks under the heat shield toward the manifold, and corroded flange interfacing with the mid-section rearward. Passed state inspection but I would prefer it were quieter (and didn't send exhaust fumes into the passenger space). Given that genuine Volvo or oem replacement is expensive since the cat converter is caught up in this I'm looking for other solutions.

Is repairing the existing cat converter possible (weld new flex pipe, patch holes)?

Has anyone had success using the cat converter replacements that sell for $100-200 on ebay and elsewhere?

Other suggestions?

Thanks.

[jonesg]

I'll be doing it myself this fall.
With low miles and no codes I would say theres nothing wrong with your cat.
I have 230K miles and I'm not changing the cat.

Heres the plan.
unscrew O2 sensors from exh.
Pull the section from the manifold to the aft cat flange.
Make a jig to hold the pipe in its proper shape at both ends with wood, once bolted up at both ends cut the flex section out, mig weld in a new high quality flexpipe, spray welds with exh paint to prevent rust.

DRess the aft cat flange halves with a belt sander.
Use all new hardware available from FCP. gaskets , copper nuts etc.
https://www.fcpeuro.com/Volvo-parts/V70 ... -8642449KT

similar to this,

[abscate]

Driveway repair possible with cool flanges from Bear River Converters of UT, courtesy of Firefox31

[enotslim]

I'll be doing it myself this fall.
With low miles and no codes I would say theres nothing wrong with your cat.
I have 230K miles and I'm not changing the cat.

Heres the plan.
unscrew O2 sensors from exh.
Pull the section from the manifold to the aft cat flange.
Make a jig to hold the pipe in its proper shape at both ends with wood, once bolted up at both ends cut the flex section out, mig weld in a new high quality flexpipe, spray welds with exh paint to prevent rust.

DRess the aft cat flange halves with a belt sander.
Use all new hardware available from FCP. gaskets , copper nuts etc.
https://www.fcpeuro.com/Volvo-parts/V70 ... -8642449KT

What about using the manifold-to-flex-pipe section from a complete replacement part ($100-200 total, manifold to aft cat flange) and welding this to the existing cat to aft cat flange? The flange could also be replaced using abscate's suggestion if necessary. Seems like alignment for welding would be simpler and fewer welds should be better other things being equal. Could test the intact replacement part first on the off chance that the replacement cat doesn't throw codes - then keep the existing cat if needed in future. Maybe the replacement flex pipe is not "high quality"?

[jonesg]

A high quality flex pipe is $40, the cheapo $25 versions don't last.
the aft cat flange can be squared up with a belt sander.