Had my 2001 XJR in a shop for something else, so I had them pull the drivers side valve cover to check what kind of chain tensioners I have. This is what I did NOT want to see, correct?

2001 XJR Cam tensioner

 

correct, those are some version of the old style and should be updated asap

 

Correct. Thats a ticking time bomb and while it might still look ok, I bet there are cracks already there on the front where the chain obscures the view. A full timing job should be done, at the very least the uppers should be replaced to prevent your valvetrain from being ruined when one of these eventually lets go.

 

Yep. Talked to the tech, and he has done a few of these before. He said he did not see any cracks with the naked eye, but I'm doing a full preventative timing chain service anyway. All new tensioners and all new chains. New gaskets all around and new drive belt and supercharger belt as well. Water pump was done about 6k ago by previous owner, so not doing that.

 

Perhaps the most infamous flaw of our X308s. Plastic tensioner.

Always Wonder what the hell did they think about using plastic.

 

Cost.
Same thing is going on todays engines too. Can you imagine metal chaing that wears out in 40 000 miles ? Chain tensioner that has minimalistic teeth that is made to break up. Tensioner that only has weak spring in it and not teeth at all relying solely on oil pressure to do the tensioning. These kind of not so good stuff is still sold as new and better tech.

 

Planned obsolescence has always crossed my mind when I see these low quality,
highly integral pieces now and again. Any engineer worth his salt would never
design plastics into such a critical part of an engine. That is....unless he was
ordered to by the powers that be.

 

I think it was just an engineering mistake. I believe in the early 2000s, manufacturers overestimated the strength and longevity of their engineered plastics. One of my previous cars, a 2008 mini Cooper S, also suffered from plastic parts in the timing chain mechanism It was a death knell for that engine as well.