I just changed the secondary tensioners on my 1999 XJR, using the method invented by maxwdg , described here: http://tinyurl.com/nmaenv
Amazingly simple, no special tools, one-man, one morning job (I used a zip-tie to hold the chain to the exhaust sprocket). Total cost: $160 (metal tensioners online, re-used cam cover gaskets, since the old ones were still fine, and the new ones I ordered on line were the wrong ones).
A few observations: at 116,000 miles, the old (1st gen) tensioners looked fine - no cracks, only minor scuffing. I would not have hesitated to re-use them, except that the metal new ones should last indefinitely. I drive the car to its full performance potential, and it still runs as new. Most trouble-free, easy to maintain car I have ever owned.
Only needed common metric sockets, and a small torque wrench. Nothing fancier than that.
I conclude that my worries were unwarranted. Provided that 1) the car has never been overheated, 2) the oil has been faithfully changed (I have used synthetic oil, 3-5K mile changes since the car was new), and 3) you have an XJR (no VVT), take it easy on beating yourself up for not having changed those tensioners yet! And when you do, do it yourself - I was astounded at the simplicity of this method.
Despite the old tensioners still being fit for duty, I am glad I did it - peace of mind after all the disasters one reads about.
Cheers!
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I can explain in theory why this method is making two important assumptions and is therefore inaccurate, but it seems a foolish argument to the successful attempts of you and maxwdg.

I'll keep doing it by the book, since doing it twice is not an option on somebody else's car. As a DIY method it will work just fine most, if not all of the time.

If the effective length of the secondary chain has changed due to wear of the chain and sprocket teeth, or if the distance between the mounting face and the fixed-end slipper pad of the different styles of tensioners is not identical, the exhaust camshaft will not be in the right place relative to the intake cam. This difference might be minute, and could only be checked with the factory locating tools. Otherwise, you assume you are correct and you're probably close enough.

 

"A few observations: at 116,000 miles, the old (1st gen) tensioners looked fine - no cracks, only minor scuffing. I would not have hesitated to re-use them, except that the metal new ones should last indefinitely. "

While you make a reasonable point, there are many who have reported didfferent results. While one example of a broken secondary chain does not prove a symptomatic problem, neither does one case of a good tensioner prove that no problem exists.

 

did you take pictures during the process?? if so, please share.

 

No, I didn't - oil on the hands.....but it was all incredibly straightforward. I can take pics of the original tensioners if you'd like, but nothing to see. I did do a step-by-step writeup afterwards, which I can PM you if you wish. Car runs smoothly to redline, by the way. :-)
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Ipad guide

 

While the OP has a valid fix with minimal resources, I'm not as concerned as some may be. There are a couple ways of checking camshaft relationship after removal of the exhaust cam saddles. Since the primary chain and the saddles were not removed, all things being equal, its timing in relationship to crank position is still what it was before work commenced. To validate the exhaust cam timing, simply rotate the crank until the two camshaft "flats" are relative to their centerline and use a straitedge across them. Only if I found major (more than 2 ~ 4 degrees) variance in the exhaust cam timing would I break the sprocket bolt loose. If the crank position was off by more than 10 degrees from TDC with the cams at their centerline I would also reconsider doing a cam lockdown and repositioning of the cam sprockets. Otherwise, I wouldn't touch either cam sprocket bolts. Use a little paint to ident the tooth on the intake cam to chain position, and zip-tie the exhaust sprocket to the chain as a reference point before removing any bolt if you should happen to move it.

The possible risk of engine damage by putting off a replacement of the secondary followers in contrast to this method outweighs any concern I might have by using it.

Having said that, when it comes to replacement of all chains and followers, then the lockdown of the cams in relationship to crank position is really the only way to do it.

 

I'd like the step-by step if you still have it. I'll be doing this over this next weekend. Thanks!

 

Try here Alex..

http://jeg.serverhouse.com/Jag_docs/

(originally posted by oldmots)

 

I changed my tensioners this weekend with this method and it worked perfectly. We were done in 3 hours tops. At 98K miles, one tennsioner looked almost ok with a very very small crack in the housing. The other bank's tensioner fell apart as we attempted to remove it, so it's a darned good thing that we caught this when we did. I decided to so a coolant flush and power steering flush at the same time.

 

We also changed our tensioner this weekend. Our car has 103730 miles on it. My dad is a mechanic and his saying is "if it ain't broke, don't fix it". I was feeling really bad when they first took the valve cover off. The right side looked OK, until they took it out. Both were cracked. The right side fell apart in their hand when they tried to remove it. I sure am glad we changed it! We have had the transmission rebuilt, replaced the water pump and now this. Is there anything else I should be worried about?