1st i will say im no expert on A3`s as i have only had mine a few months, but have owned 1.8t`s on other models prior. 150.000mile with a good history is no problem, these engines are strong but you must be spot on with servicing!! if it has no history i would not touch it. On the b5 a4 chassis the front suspention arms are common to clonk and knock and are a pig replace if the pinch bolt is stuck on (which they normally are) i dont know if the A3`s have this issue also. Check the Turbo boosts propperly, dont expect to be pushed back in your seat like a Scooby or evo, but a turbo`ed presance will be there. If there is a rattle from the back of the engine when the revs drop after reving it its more than likley the turbo shaft rattling in which case could be expensive and a inconvinience! (spelling) check for smoke from the zorst on tick over, leave it running for 10 mins to let it warm up, normal things you look for in a new car and common sense etc. I have also read somwhere that some A3`s suffer from rust on the roof.
im sure someone will correct me if i have said anything wrong, but the main key to any Audi, is good service intervals, oil changing and just not treating them like a mk3 xr3i! Look after it and it will look after you! simples!
I SAID ALL THIS TO A NEWBE THE OTHERDAY.
I JUST COPY AND PASTED IT AS IM LAZY! HOPE THIS HELPS GARY!
