Nasty sound from brakes - A3
 

Hi,
Hope someone can help me to identify a rather annoying sound from my brakes - as my Audi dealer cannot :-(

It is an A3 Sportback Ambition 1.6 TDI 110 hp, automatic transmission, bought new from factory October '15, now app. 14.000 km.

It's hard to describe the sound, but it kind of reminds me of Chewbaka from Starswars having a cold ;-)

I have put some recordings in Dropbox:

https://www.dropbox.com/s/3qvg27p4cr...kes-1.mp3?dl=0
https://www.dropbox.com/s/dqts7yps4a...kes-2.mp3?dl=0
https://www.dropbox.com/s/ryyxf2byxi...kes-3.mp3?dl=0
https://www.dropbox.com/s/o0ntol5ei8...kes-4.mp3?dl=0
https://www.dropbox.com/s/u8d13x90li...kes-5.mp3?dl=0
https://www.dropbox.com/s/gi0vdn3qjq...kes-6.mp3?dl=0
https://www.dropbox.com/s/hkuzlpigqd...kes-7.mp3?dl=0
https://www.dropbox.com/s/2zb85bcmcp...kes-8.mp3?dl=0

It is an intermittent fault and it's not been possible for me to identify specific conditions under which it occurs, only some general characteristics:

The sound appears when maneuvering the car after parking - the first 10-20-30 meters, but then disappears and both when driving forwards and backwards (however more frequently when driving backwards).

It's partly related to weather conditions (lower temperature, higher humidity and rainfall/snow). Most frequently I've experienced it in winter conditions (below freezing point, but never below -10 Celsius/14 Fahrenheit) or during rainfall, but also when above freezing point (+5-7 Celsius/44-50 Fahrenheit) and dry weather.

The sound is not related to parking for lengthy periods, e.g. I have experienced several times that it is present even though the car has only been parked for a few hours (and that after after driving at least 20-30 km/12-18 miles and definitely having "clean" brakes).

Several times I've experienced a pattern with the sound appearing when leaving home, driving 20-30 km and after parking ½-1 hour it's there again, completely the same sound, that disappears after maneuvering. After parking in ½-1-1½ hours is the same pattern.

The sound is of a completely different character than the ordinary "squeaking sound" you hear when maneuvering a car with automatic transmission.

My Audi dealer has tried several explanations, including that it is related to the rust can be seen on the discs in wet weather, when a car has been parked for some time - however, the discs have always been "clean" - and the sound is not the same as the one you can hear, when the discs are in fact rusty after parking for a while.

I've read about pebbles getting stuck in the brakes, but it seems unlikely to me, that I would get pebbles in the brakes so frequently as well as I'm mostly driving ordinary paved road in the city - not offroad in any way.

A mechanic at Audi said that "they had experienced this before" on exactly this model, but could not give further explanation - which also puzzles me a bit if it's something as "trivial" as pebles in the brake.

Looking forward to suggestions - it's really annoying - and the Audi Dealer tries to fob me off with "that's just the way it is, get used to it..."

"Chebacca noise" is a really good description of that. It sounds to me more like a metal groan, like lightly holding the brakes and letting a vehicle creep up or down a hill. In which case it may be something engaging the brakes and disengaging afterwards? I'm questioning whether it's the brakes at all; if it is, the first thing I'd check is whether the sound is coming from the front or rear.

If it's the rear, check the parking brake cables/assembly to see if they're frozen/stuck.
If it's the front, perhaps the caliper pins need greasing; another way to test this is to go on a short drive with minimal braking, come to a stop and feel near (don't actually touch) the brake rotors. If they're hot, when they absolutely shouldn't be, your caliper is holding on and refusing to let go and the pins need to be greased. If it's only hot on one side, that's the one that's sticking.

Both of these are relatively easy checks; your dealership mechanic sounds a little...unseasoned for this type of work. Hoisting the car off all four wheels and putting it in drive should've been one of the first checks, to determine if it's brake-related or load-related. Meaning if the car is actually moving versus the drivetrain and wheels moving. Taking the pavement out of the equation is usually a first-step diagnosis for mechanics able to think outside the box.