hi Trevor it was the power steering fluid that was leaking. I knew it wasn't coolant because that's red and when the level dropped the power steering was starting to groan and felt a bit heavy. The S8 5.2 V10 & the 6.0 W12 are different to all the other A8s. Because the engines are so big room is an issue, the power steering reservoir is under the the air box and a few other things and a pain to get to. Big difference to the 4.2 v8. Will send pictures hopefully this could help other folk that come up against this. Thanks for heading me in the right direction & you were correct it's not high pressure in them pipes. Thanks Trevor 👍