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I have the known noise on start up so going to give the upper chain tensioner replacement a try. Have read lots of posts. Seems straight forward enough but if any one has advise please feel free to post away. I’m haven’t quite worked out how the tensioner fires yet and if the cam sensor has to come out. I guess all will become clear once the bonnets up and the hands are oily.

This is my upper chain it appears tight. Do I need to replace tensioner?

Not a bad job. If changing out the later adjuster apply pressure to chain so piston doesn’t fall into engine. Original type I think can be secured with an Allen key inside end cap.
Before removing cam sensor align marker dot in window marker and when done refit in same position.
When done I wound over engine without plug leads connected to build oil pressure and so allow tensioner to tension chain before starting engine .

The above worked ok for me doesn’t necessarily mean it’s correct procedure. Hope it helps someone but proceeded with caution.

Just to add my 2p worth.
Very often it’s only the O-ring that actually fails on these. That’s if the rattle is at start up only. The o-ring on the outside of the tensioner is what holds the oil pressure on the tensioner with the engine off (the tensioner operates with oil pressure).

I have replaced the o-rings on a good number of these. It’s worked every time. Same for XJ40.