[V6-12v] Experience changing cats

Tom Christiansen tomchr at gmail.com
Mon Mar 5 12:11:24 EST 2007


Thanks that's just the information I was after. Do you happen to
remember which size bolt it was?

BTW, that Quicksteel lasted about 15 minutes. It now has the same
hairline crack in it as the down pipe. Dammit... I guess I'll have to
replace the cat afterall.


On 3/4/07, Frank Chapchuk <chapchuk at hotmail.com> wrote:
> Tom,
> There are studs in the header. When I did mine I was able to remove the cats
> by either taking the nut off or breaking the stud. Breaking the stud is no
> big deal. With the cat out of the way I just drilled out the broken stud and
> replaced it with a stainless steel bolt and nut. No need to tap the header
> to install a new stud. Just use a bolt.
> I replaced both cats......after failing emissions. Make sure the O2 sensors
> are working correctly or the new cats may get runied. Mine just died from
> old age.
> Frank
> ----Original Message Follows----
> From: "Tom Christiansen" <tomchr at gmail.com>
> To: "Audi list" <v6-12v at audifans.com>
> Subject: [V6-12v] Experience changing cats
> Date: Sun, 4 Mar 2007 14:08:48 -0800
> Folks,
> As I was crawling around under my 1994 90S (B4) patching the down pipe
> for the driver's side cat with Quicksteel, I discovered that the cats
> shouldn't be as hard to replace as I had feared. Everything is
> reasonably accessible. Most of the bolts downwind of the cat look
> pretty pristine, but I wonder about the three nuts on the exhaust
> header. On most cars those are notorious for seizing up. But I noticed
> that they are lock nuts. So maybe I could be in for a bit of luck...
> Does anyone have experience to share in this regard?
> Is it three studs in the header? Or three bolts? Will I need to cut
> the bolts or do the nuts generally come off without too much fuss? Are
> the bolts secured from the top so they won't spin as I turn the nuts?
> Would you replace just one cat? Or is it normally encouraged to
> replace both at the same time?
> Thanks,
> Tom
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