About 3 weeks ago i went out to my Allroad (03 plate 2.5TDi) to find it sat on the floor. The suspension had bottomed out all round and no amount of pressing buttons etc would bring it up again.
I returned to it later that day and did manage to get it up to level 2 but overnight it dropped again. I left it in Jack mode after raising it to level 2 (it took a while!) and the following day it had dropped to the nearside rear so was pretty obvious I had a leak that side.
However after so much compressor work it was starting to struggle so I ordered a repair kit from Andy (thanks Andy!), replacing the piston ring in the compressor was pretty straight forward and now the car would lift again so I could set to work on finding the location of the leak. Spraying a solution of soapy water on the rear shock resulted in bubbles straight away. Right where most people say they go (where the bag folds under itself at level 2). So i got the car up to level 3 and left it there (didn't leak at all) while I organised a replacement air spring. I actually ordered both rears as the drivers side didn't look in great condition either....
I found this video which i used as a guide to help me Installation of Arnott Spring/Bilstein Shock 2000-2006 Audi Allroad Quattro A-2133, A-2252 & SK-2256 - YouTube (only thing i didn't do was disconnect the handbrake cables - not needed!)
After spraying all the bolts with penetrating oil twice a day for three days I set to work, I'm glad to say that the penetrating oil did the trick and everything came out very smoothly following the guide above. I had to use my trolley jack handle to lever the spring down a little bit more to remove it but it came out pretty easy.
You WILL need an airgun to remove and replace the top nut so please bare this in mind if attempting a DIY. Luckily my father is a mechanic so I simply got both springs off and then took them to his place of work to disassemble and reassemble. I would imagine a friendly local garage would also do this for you for free / very small fee.
Everything assembled and it all went back together nicely, my only tip would be to make sure that the level sensor arms are pointing out towards the side of the car rather than inwards when you bolt them back in place (easy to have them facing inwards and then brake the plastic arm )
After putting the car back down on the deck (supported by a jack each side to help the airbags inflate) and removing it from Jack Mode everything filled up nicely and the car will happily raise from 1-2-3-4 and back down again. Much quicker than it has ever done in my few months of ownership! The rear end also feels tighter than before but of course that might be my imagination!
I hope this post helps even one person that might contemplate doing this job themselves, with both springs and the compressor repair kit costing me less than £400 I think I've saved and easy £2k on stealership prices!!
I've already started soaking the relevant bolts at the front in anticipation of them failing! Hopefully they will hold out until the spring when I will do them in the better weather!