[A4] o2 Sensors Replacement Help

Gregory Megara megara at mac.com
Wed Jul 6 12:32:58 EDT 2005

Yeah, tell me about it. I had my cat out when I put in a new clutch and I figured I may as well change the post cat o2 sensor while I had it out. There was no way I could get it to fully screw out. I used some liquid wrench and let it sit for a night, but I couldn't get it to unscrew easily.

Unbolting the axhaust would be a requirement for me were I to attempt that again. Getting a wrench on the sensor while the cat is bolted up is not fun.

I would do it this way:

1. Remove airbox.
2. Remove pre-cat sensor.
3. Assuming you have a 1.8t, remove the turbo to cat studs/ nuts, or loosen them the best you can.
4. Remove the downpipe on your exhaust.
5. Remove cat.
6. Attack the post cat sensor.

You might have to jump between #3 and #4


Message: 8
Date: Fri, 24 Jun 2005 23:57:58 -0400
From: "Calvyn" <Calvyn at stny.rr.com>
Subject: [A4] o2 Sensors Replacement Help
To: <v6-12v at audifans.com>, <a4 at audifans.com>
Message-ID: <200506250357.j5P3vhIU011119 at ms-smtp-02.nyroc.rr.com>
Content-Type: text/plain; charset="us-ascii"

Hello all.

Anyone know any tricks to removing the post-cat o2 sensors? The
front ones are a piece of cake thanks to a nice deep-well 7/8 socket, a
universal, and several extensions, but the rears are a real PITA. I can get
a 7/8 line wrench on them or a 22mm crescent wrench. I've tried penetrating
oil and heat but neither is budging. Do I need to unbolt the exhaust from
the manifold and drop it down to get a better grip on them? I fear that
because the exhaust is looking rough and don't wanna monkey with the rust
that might be holding it together. :) Saw on the AudiWorld forums something
about using a crowfoot.

Any and All suggestions are welcome except for one who says to take
it to the dealer to do. :)


'96 A4 2.8 V6-12v FronTrac

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