I have an 1999 Audi A6 wagon. Ihavean unknowncyclingpump noise coming from the frontright passengers side. It cycled on and off all night even when shut off and seems to have killed my battery. Does anybody have any clue what caused this, and exactly what it is? Thanks

 

What engine do you have?

 

could be secondary air pump or EVAP valve im sure some one else has this problem ( badluckaudi )

 

I have the 2.8.

 

I had the similar problem with my '98 A4 2.8. The secondary air pump gets corroded inside over time and gets loud. The pump only activates when the car is cold. It supplies additional air, from the air filter box, to the exhaust gas. The cold engine calls for more fuel but this richer mixture sends a richer (more polluting) gas to the catalytic converter. The additional air is used to "dilute" this rich exhaust in order to reduce pollution at start-up and to protaect the innards of the converter. This is probably more that you wanted to know!
The pump has to be replaced. It is located far under the right headlight and requires the bumper being removed to get access to the bolts and plastic tubing (at least on the A4). I bought a used pump from Shokan Coachworks in New York for $150. A new one is about $275. Hope this helps.

 

Mine is similar and asked the same question. Only this is the first night I am experiencing it. I was up in the colorado mountains last night where is was below freezing all night. I went out for breakfast this AM and it manifested itself in my garage at home this afternoon. It's probably the secondary air pump going on and off. High speed pump, noise, right?
19audi98

 

THANKSguys and yes 19audi98 that's exactly what is sounds like, first my steering rack then this in less then a month from buying it, but I still am totally digging this car. Thanks again.