currently have 68k on my 99 xk8, not sure if the uppers have been done or not. have a good warranty that will pay off if they fail, but I don't want that of course, any idea how long they might go? I've heard as much as 100k before the plastic ones fail.

 

There is no reliable rule of thumb for when they will fail. At 14 years of age and 68K miles though you are certainly in a high risk area. Replace them. Why bet your engine on a piece of cracked, brittle plastic?

 

I have had two cars that had their tensioners changed before 50k miles . . . under warranty. One of them, a '00 had the tensioners changed at a little over 40k, a little over 80k and at 106k. All for good reason I assume. The 106k, with only 26k miles were both split a third of the way up when I personally changed them.

 

is it necessary to do all of them and the guides or can I get by with just doing the uppers?

 

They all deteriorate, including the guides.

The secondary tensioner failures generally have the most disastrous consequences and sometimes come without audible warning..so these are a must.

The primaries and guides usually make an audible rattling as they deteriorate but generally do not cause the engine to fail disastrously.

Doing all is the best option, but if funds are tight at least the secondaries should be done.

 

Same car, same miles, both upper tensioner bodies cracked and one slipper end came off in my hand. Don't be a fool, change them asap. Sorry for the harsh language, but it's a no-brainer unless you want a new engine.

 

+1 to all who have responded.

My '01 made it to 100k, but they were indeed cracked when replaced. I just got lucky.

Based on mileage, my guess on the 2 repairs prior to yours is that they used 1st or 2nd gen tensioners again.

 

how easy is it to change those secondaries. I assume they are the "uppers" I can get to with just taking off the valve covers. apparently, you just zip tie the cam sprocket to the chain and undo the exhaust cam caps to lift it up enough to get the tensioners out. is that correct?

 

Basically, yes. I believe if you check in the how to sticky you will find a procedure.

 

Read through the instructions and many posts on the forum on this subject. You should be able to benefit from other peoples experience and do it yourself for under $250 including the tensioners, new bolts and gaskets.

 

the tensioners themselves? or the valve covers

 

The new style tensioners require shorter bolts.

 

After reading the various posts on this subject, I bought a pair of the latest metal - bodied secondary tensioners for £75 and got all set to do the job: guess what, when I lifted the cam covers they had already been replaced, doh! So if anyone wants to save a few pounds, I'll pass them on for £65 including UK postage; they're new in the bags, never even been opened! PM me if you're interested,
Cheers,
John