Thanks a million, appreciate the insight. I did manage to get the tensioner out, what a pain with so little clearance. So it was very weak spring, so I assume that is not what is needed to keep chain tight. I looked in oil filter housing, no pieces, so will replace tensioner and see if that is issue. I am keeping fingers crossed, if it solves problem it would make me very happy, hate to think about doing guides at this stage of vehicles life, but I love the X5.