So, I'm scratching my head on this one. '01 base XJ8 w/ 150K had new tensioners done 3 yrs ago. Recently, I get what might be called a tensioner rattle on cold start-up. Rattle goes away within a couple of seconds and does not occur again regardless of the number of stop/starts on a drive. I'm told new tensioners don't go bad. Recent oil change had no effect. A club member suggested the VVT actuator is loose. The rattle is definitely in the left-front top of the motor.
Soooo, any guesses?

Dave in AZ

 

The metal tensioner has a ratchet mechanism that keeps the foot extended when the engine shuts off. There was at least one report of this failing that I recall. So it might be worth the effort of taking the cover off to see if the tensioner is collapsed.

 

Thx for the lead. Wondering if this is an "engine fail" potential issue. Time and money prevent immediately addressing the problem.
Dave in AZ

 

If the tensioner has collapsed it's possible for the chain to skip teeth, and that will result in bent valves. This may not be your problem but removing a cam cover is a pretty simple operation.

Were both primary and secondary replaced?