I have a 2006 A3 2.0T with what seems like a Haldex issues:
When I pull away everything is fine, then when the rear wheels are required to be engaged (by the front wheels losing grip) there is a clunking noise. I have completed serveral tests:
1. Pull Handbrake and the haldex is disengaged car drives fine (front wheel drive only)
2. Push the brake pedal when driving, this is meant to complete the same as point 1, nothing happens
3. Changed Haldex controller, again no change
4. Pull Fuse 31 out and car runs fine, as ESP light stay on and AWD system is disabled.- This is how I'm using it currently.
I am told the following
1. Try changing the oil - I found out the car had Haldex oil changed at 20K and this problem occured at 60K when it should had been changed at its 40K server, it was 20K to early so this may have caused the issue to occur.
2. Try changing the pre charge pump - This seems to be the case for 8L engines, so unsure if this is the case with 8P engines?
3. New Rear Diff - Money and effort in this, but happy to do this if it is 100% the haldex and not a speed/ABS senor, which can alos cause issues?
My conclusion is the haldex is not releasing, or the signal is not getting to it to tell it to release, so its stuck on hence the noise.
I need to find someone around the kent/Essex area who has Vagcom or can help diagnosis the issue, spoke to my local Audi dealers and they want 160 Per hour for diagnostic, which I can't afford. (annoying as Jaguar do a full diagnostics for a fix price of £60)
I live near Orpington in kent, but am happy to travel to someone if they can help me understand what the actual issue is before I start changing stuff.