I just got this XJR last week, it has a August 2001 build and I can't find the engine serial no. So I just decided to but a new metal tensioner thinking it still had the 2nd gen plastic ones and voila! See the first picture, the tensioner is plastic and has crack, trouble waiting to happen. My Jag has 83k miles only. Second pic shows newly installed metal tensioner.

 

For some reasons I can't attach the second pic so I'll just add it here

 

Proper preemptive strike, kudos.

 

Good job, none too soon!

 

Good work!

 

Still strange how different things can be.
Did mine last week, and the plastic tensioners came out without a single crack.
almost 70.000 mls. on them.
Still happy that I did those, it feels much better.

 

I'm thinking local climate accounts for a lot.

 

2nd gen added the spring, but it only made it rattle less before it failed.

Nice save!
Vector

 

Did you place all of them or are you still happy playing engine damage lottery?

 

And the spring stopped giving us an audible warning of it's impending failure, poor decision on jaguars part.

 

I thought that the 'rattle' counts for the gen 1 primary ones, that the secondary let go without a warning whatever the generation?

 

"Usually"

Gen 1 secondaries "might" give you some warning rattle, 2nd gen? Not so much because of the spring, usually.

All primaries usually rattle before failure, but failure there is not usually catastrophic.
Vector

 

Now here's the passenger side secondary tensioner, see how the plastic has been taken off the metal piece. How the chain has practically sawed the metal part, yet before I opened the valve cover I never heard any metal to metal grind. I have saved a Jaguar from catastrophic failure, feels good to catch this in time.

 

That's a good feeling isn't it? Now you're "hooked" though. Saving Jaguars from extinction will be in your blood from now on....

 

Again, don't just do the secondaries. Your chains have worn underneath. They are now less stable and can break... I only ever do the lot or nothing... 4 or 5 times now, without my own V8.

 

Daim, where do you get your info on breaking chains from?
I read several disastrous cases of jumping or breaking secondary chains over the years, but never on worn primary chains as a cause, just cracking guides.

 

Now you need to ask "where did that plastic go?"

In the oil pan.

 

Great catch!

 

Lucky the plastic slipper didn't lodge between the exhaust cam gear and chain and snap it- very common.

 

4-5 times! In how many miles?

Well I agree that the secondary chains may be worn on the outside of the chain where it touched the metal part of the tensioner, but that has nothing to do with the primaries.

Replace the secondary chains if you want to be safe, but they are probably OK.

Experience has taught us that the primary system lasts a long time and gives plenty of warning before it fails, which is not catastrophic anyway.

Secondaries are an easy DIY, primaries are a big job requiring specialized tools and knowledge.
Vector