[V6-12v] Experience changing cats

[Clive Young]

Cat Nightmare 

Well mine isn't going as smoothly as Toms for sure ..

Couldn't get the car up the ramps as they kept slipping out as my front air
dam hits the ramps before the wheels .. I tried using wood but that didn't
work either. 

Eventually got it on and bolts holding the cat to the exhaust were
completely rusted and the nut was indistingusishable. Cut them off but the
bolts were rusted into the flange I needed. I had to clamp the flange, cut
the head of the bolt off and the broken piece, used a cobalt bit to try and
drill it out ,,.useless... but made a small dent , used my impact hammer
with a point bit to eventually drive out the bolt pieces.. I was lucky there
and so far I am only in about 8 hours. Gets better. The exhaust manifold
piece was fine but I only have threads right were the nut was , above it and
below it are completely disintegrated. I am sure these are going to snap off
on reassembly. 

My cat is also about 1 cm to short . and if I seal it for no leak at the
manifold end I am about half a pipe off on the exhaust end. 

Tom where do I adjust the rest of the exhaust to bring it forward? I can't
see how to do that because both sides are welded together further back and
the other cat is still in place ! 
What is that sleeve and the two clamps for right behind the test port on the
exhaust ? 

Also the bolt on the spring holding the pipe totally snapped off. . The
other cat is the original and has 3 springs on the bolts between the cat and
the outlet pipe. The problem there is the flange I need is rusted right
through on all 3 bolt points so I AM SCREWED IF I REMOVE IT . There is no
way to put a new flange on is there ? 

Anyway I fight on .. 
Ps when I took the old aftermarket one off it was TOTALLY HOLLOW and I
passed emissions anyway ... 



-----Original Message-----
From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com] On
Behalf Of Tom Christiansen
Sent: Monday, March 05, 2007 12:11 PM
To: Frank Chapchuk
Cc: v6-12v at audifans.com
Subject: Re: [V6-12v] Experience changing cats

Frank,

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.

Tom

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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