youngspeed

.....its a vacuum pump drawing warm air to heat up the brake lines. Any truth to this. Anyone with their 2 cents pls...

Muhammad

Follow the line from the brake booster and see if you can find any obvious cracks or leaks.

I did it with the car running, so I could push on the hoses in various places to see if there were any obvious spots. Indeed there were.

If you find the spots, you can use electrical tape as a temporary solution until you replace the hoses (they're fairly cheap).

PaulW

It's probably your air pump which pumps air into the exhaust, here's some pics from somebody with a 4.2 that recently asked the same questions, these are pics of the A8, but probably the same for your car, BTW, what year is it?

And no, you don't need to warm up brake lines.....I would change mechanics if somebody told me that.

Here's the pictures, it's almost self explanatory. The pump is driven by a motor in the air box

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/ai1.JPG">


The big diaphrams open up and the pump pumps air into the exhaust

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/ai2.JPG">

There is a small solenoid valve that ports vacuum to the top of the big diaphrams

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/ai3.JPG">

The ross-tech tool can test the component, and I've tested them before, and the air pump is quite loud, probably it.

youngspeed

Brilliant. Thanks! Can anyone say new mech?