I had a rattle noise for two years on my 1989 xj40. (its my baby and only drive it a few times a year) The guy that works on my cars is a very good friend and a Jag and Rover only shop. So, he knows the car very well. We tried everything even a new a/c comp. still there....
Well the other day I was at the shop looking again.
We did it!!! The crank bolt was loose!!!! How?? We dont know.
Very hard to find not something you would look for.
If my long story helps one person its worth it.
Good Luck, Brian.

 

Glad, you got it sorted out
Moral of the story is like you should not overlook anything lol