[V6-12v] Experience changing cats

Sun May 20 23:48:10 EDT 2007

Clive,

Sorry to hear about your rocky ride with the new cats. My car has the
California emissions package and I'm the second owner. So I pretty
much assume it was driven in California for the first ten years or so
of its life. Hence, no rust anywhere. Great for the home mechanic.

The driver's side cat on my car did not have springs at the mounting
points. The passenger side cat did... I don't know if they are really
necessary. I think not.

Getting the studs out of the header would be a royal nightmare.
They're probably hardened from the heat. You might be able to drill
them out. Or you might find some abrasive hole making tool can make it
work. A Dremmel tool or something... But then you still have to get a
bolt on there somehow. There are also stud removers...

In my case, the threads on the header studs were worn. But I was
careful when I attached the new nuts and didn't strip the studs. It's
holding up this far.

About the rear seal or donut as you call it. It looked symmetrical to
me. So I don't think it has a preferred orientation.

Yeah, my replacement cat was about 1 cm short too. I'm glad you
figured out the sleeve bit.

Tom

On 5/19/07, Clive Young <cyoung1661 at rogers.com> wrote:
> 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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