odd sound on cold start

[Castor79]

Hey,

When I start my C63 from cold I am hearing a sound kind of similar to a vacuum cleaner coming from the front of the car. It only last around 5 seconds and then shuts off.

No change in the car, just wondered what it might be... anyone else getting this?

 

[StephenSJason]

I think I know what you mean, and if I'm right it's the secondary air pump helping to warm things up. You might find that just before it comes on and the alternator loads, the revs drop slightly and the exhaust becomes deeper for a moment.

 

[R1NGA]

I think I know what you mean, and if I'm right it's the secondary air pump helping to warm things up. You might find that just before it comes on and the alternator loads, the revs drop slightly and the exhaust becomes deeper for a moment.

Most likely indeed. Pumps air into the exhaust to compensate for the enriched cold-start and keeps the suits in Brussels happy. Usually a hopelessly unreliable unit on Audi's and often removed and 'coded-out' of the ECU to keep the CEL at bay.....

 

[Castor79]

great, thanks both. It wasn't something I had notice until someone else started the car and I was stood outside - the car sounds even better from outside!!!