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D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

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Old 22nd September 2018, 12:41 PM
Nognar Nognar is offline
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Default 2002 A8 D2 2.8 QS Catalyst

Afternoon all,

I am still going through the list of jobs on the new D2 runabout and have noticed a rattle when cold.

Looking into it more I suspect the cat is breaking up inside and causing the rattle. Interestingly the Passenger side 2nd cat has been replaced but not the drivers side and I am pretty sure that's the problem.

What I wanted a little help on was the correct part numbers. Looking at the car the 1st and 2nd cats on the left and right both are in two sections on the car so you can replace each, hence the 2nd cat passenger side has been replaced.

Looking at ETKA (4D1253058), eBay and the like I can only seem to get the drivers side replacement as one pipe with the first and second cat in one unit, not two parts as is currently on the car.

BM Cats do the BM91085H which appears to be correct but its one whole part, I cannot seem to buy as its actually on the car now.

Not the end of the world as BM91085H is only £150, I just wanted to check with the wise collective I was not going mad here?
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2001 Audi A2 1.4 SE - Jaipur Red Pearl
2002 Audi D2 4.2 S8 - Ming Blue Pearl
2002 Audi D2 2.8 A8 QS - Audi Silver
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Last edited by Nognar; 22nd September 2018 at 12:44 PM.
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Old 22nd September 2018, 12:52 PM
MikkiJayne MikkiJayne is offline
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The driver's side cat and downpipe is normally one piece. Its only the passenger side which splits in front of the cat. I've seen aftermarket cats which have both pipes split though (Big Red has them) so perhaps both have been changed at some point? Or someone has split the driver's side and welded in a joint for some reason (usually changing the cat).
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Old 22nd September 2018, 12:58 PM
Nognar Nognar is offline
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Thank you and appreciated as always.

It looks OE but who knows what's happened over its 16 years of life. I will order the BM one as one part.

One question as I suspect you may have done this before, how difficult is access for the bolts on the drivers side where it connects to the manifold?
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2001 Audi A2 1.4 SE - Jaipur Red Pearl
2002 Audi D2 4.2 S8 - Ming Blue Pearl
2002 Audi D2 2.8 A8 QS - Audi Silver
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Old 22nd September 2018, 02:11 PM
MikkiJayne MikkiJayne is offline
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The bottom two can be reached through the wheel arch from underneath using a ring spanner, assuming they are the original nuts and not rusted up. If they are rusty then a strong 1/4" ratchet and 6-sided socket is in order. The top one is best reached from underneath from beside the cat using a very long extension bar and universal joint. There's no room behind the engine to get to it from the top unfortunately because of the SAI rubbish.

Don't forget to disconnect both O2 sensors - one on the bulkhead and one under the plastic cover behind the airbox.

It takes a lot of wiggling, but it will come out. Its worth removing the driveshaft heat shield from the gearbox as that gives a bit more wiggle room iirc. Consider the driver's side gearbox mount may also need to come off - it does on the S8 with the 5HP24, but the 2.8 has the smaller 5HP19 so it might squeeze by.

You'll probably need to get it quite high in the air to get it off so you have room under the car to rotate the pipe. Again, the S8 needs this. Can't remember for the 2.8.

Good luck

Last edited by MikkiJayne; 22nd September 2018 at 02:15 PM.
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