US version 2004 XJ8 46,000 miles. Only use Mobile One synthetic. When it sits for a period of time, like overnight, upon start up there is a very loud metalic sound that lasts just a few seconds. Only lasts a few seconds then quiet again. Sounds like timing chain hitting cover or guides. Starting after it has been driven during the day it will not repeat. I have seen several folks on various forums with this same condition but none of them ever posts a final resolution.
I don't believe it needs a complete chain and guide replacement. Thinking hydraulic tensioners on the timing chain which may drain overnight??
