Hello, i just bought my 2004 a6 s-line three days ago. It has about 84k miles. We test drove it and everything seemed fine, but the day after i bought it it started making this weird noise. After letting it sit all night, i drove it to school and it was fine. After school, i went to start it and it made this loud noise that sounded like a jet plane taking off. It sounded horrible and i was pretty worried about it, but the noise stopped after about a minute and i was off on my way. It seems every time i let it sit for a while (over a couple hours or so) it makes the same loud noise. I'm pretty sure its my Secondary air pump, because a few people on here have had the same problem as me, and the noise sounds the same.

The sound is pretty intense so it's kind of worrying. I've heard the pump has something to do with emissions and has something to do with the catalytic converter, which would be pricey if it went out. I've read a lot and seem to be getting different answers. Do i NEED to have it fixed, or can i just leave it how it is? Can i fix it myself (some guy on youtube said he fixed it with 12$ worth of rivets)? Also i read something about Audi's 2.7t engine having some major recall on the cat converter and replaces it for free under 90k miles. Does mine need to be replaced?

I just really have no idea if it's a major problem or something that doesn't need to be fixed asap or at all. Any help would be GREATLY appreciated.

thanks for your time

 

secondary air pump and cat converter are not necessarily related. if your car was having cat problems it would set a code and your CEL would be on. common wisdom with the SAI pump is that if you can hear it, it is working even though it sounds bad. I've seen a DIY where a guy "rebuilt" his as a temporary fix. I believe there are also options to delete the pump from the system but I think you need an ECU program to keep it from setting an emissions code (not a big deal unless you have to pass an emissions test).

replacing the pump is pretty easy. definitely a DIY but the part is ludicrously expensive (for what it is).

whatever you decide, it is not a big deal. will not affect your performance. does not need to be fixed right away.

good luck

-not an expert, just an enthusiast

 

maybe a used one from
() Force 5 in NH
Force 5 Automotive
() Shokan Coachworks, Audi parts 1-800-All-Audi

() Car-Part.com--Used Auto Parts Market

 

SAI pump noise is normal. It happens especially when it is cold outside to recirculate exhaust back into the intake. I wouldn't worry about it.

As for the catalytic converter, unless you have a related CEL on, there is nothing that Audi will do for you.