I have got an audi tt 1.8 Quattro (225) (140000 miles on the clock) when i start up there is a clicking noise that sounds like it is coming from the cylinder head, car runs fine but I get the same noise when I switch the engine off from idle. The noise does not happen if I turn off with a few revs, what is causing this. By the way when I changed the oil it was ok for a week but then the noise returned. What is causing this? Sound only last a couple of seconds at most and sounds like a ratchet wrench being turned