ive recently bought an a6 2.5tdi avant quattro off my sister...im constantly having warning lights come up..at present it has a brake warning light on and the glow plug light flashers if you dont touch the brakes for 5 mins...ive changed the brake switch..it has different bulbs out everyday yet the following day there back working again......ive just broke down with the fuel gauge showing between quarter and half...fault codes show the brake problem yet its had new brakes(inc discs)..now the aa bloke is saying it stopped because theres a huge fuel leak underneath(which i thought was oil.and was told that to) ive put £20 of diesel in and it still wont start..