hi,i have an audi a4 avant tdi but mines the b8 and i see your d/i/l's is a b9....hope her thermostat is not in the same place as mine as its a pain to do(see pics)mine is the thermostat(circled pic 1) surrounded by the casing it comes complete.i had to remove the alternator(pic 2 expanded view) to get to the torx screws and to be able to manoeuvre the thermostat and casing out....what a job getting it out,and back in.i had to put a clamp on the pipe to the right of the thermostat(see pic 3) to stop a leak i got after putting it all back together Grrrrrrrrrr.lol.....good luck hope your d/i/ls is easier to do than mine was.i only changed the thermostat as a precaution as i had changed the cambelt aux belt and rollers and because of the high mileage.kind regards stephen