Recent (99) XK8 owner here. I notice that virtually all the recommendations and tutorials for replacement of the chain tensioners only replace the upper ones. do the lowers really not cause problems, or are they just not changes because of the difficulty involved?

Just curious,
Russ

 

The plastic upper tensioners are subject to the much higher heat of the heads and have a much higher failure rate. The secondary tensioners can fail at any time at any mileage while the primary guides often fail before the primary tensioners and are typically good for over a 100k miles.

 

Thanks for bringing this up. I had been wondering the same thing, why emphasis on the secondary tensioners over the primaries. My "2002" XK8 manufacture month was June 2001. From information gathered on this forum, I believe I have the second generation, partial-plastic tensioners installed shortly before the transition to all aluminum tensioners in late summer 2001.

I still need to eyeball the tensioners to verify, but if I find plastic would others suggest changing the secondaries to all aluminum now and save changing the guides and primaries for a later date/higher mileage? I have with about 42000 miles now as the beauty sits in heated garage, hibernating with battery minder attached.

 

If you find plastic you should change them without delay.
Most people who DIY do only the upper tensioners as it is a relatively simple job
and failure of the primaries is unlikely to have the same catastrophic result.

 

My June '01 manufactured '02 MY had the plastic tensioners and unless they have been changed yours will also.

 

Replaced all tensioners & chains on my 2000MY a couple of years back at 95k. The removed tensioners were plastic & all had signs of hairline cracks appearing in the bodies & the contact pads.

 

The difference to note on primary vs. secondary tensioners is that this is an interference engine. Meaning that if the secondary tensioners fail the engine bites itself and subsequently your wallet.

Failure of the primary tensioners will not cause the same level of damage and do give you some warning with a "rattle" at startup. The secondary tensioners will go without any warning with catastrophic results.

 

If you can DIY then a change of the secondary tensioners is essential. If you are going to fork out for a garage to do it then having the whole lot done has some advantages. Whilst the primary tensioners rarely show big problems, the guides do and should be replaced. Issues don't usually occur at less than 50K miles but I have never seen anyone post that at a greater mileage than this that their tensioners (1st or 2nd gen) didn't have cracks in the tensioners and guides.

 

Exactly, if you're up in the higher mileages its as well to go in once & do the lot, you are pretty much assured of the next 100k being trouble free - which, the way some cars get used could be 20 years, so if you amortize the cost it aint so bad even if you have to pay for it to be done, and, if you want to sell its a definite plus point.

 

The car in question is currently mid-USA somewhere, in the belly of a transporter, and due to arrive here in Oregon in a couple more days, so I haven't been able to put an eyeball on it yet in person. will I be able to see the primary tensioners from the top with the valve covers off? The car is claimed to have had all it's upgrades and maintenance, but I was born a sceptic and like to see these things for myself . hopefully they were all upgraded with the aluminum parts already, and it will be a moot point.

Thanks for the input so far,

Russ

 

Here is a procedure for replacement of all chains, tensioners and guides. Lots of pictures.

Tmingi chain and tensioner replacement

 

Thanks for the link. Nice to see photos

Russ

 

Another how to on the tensioners

Link JagRepair.com - Jaguar Repair Information Resource

 

Thanks Gus

 

Note, when you pull the Vcovers off you will pull the plug boots, beware any oil in these wells, if so you will need a seal kit (since u already have the vcover off it's easy) some have reused what was on but with the age I'd replace them so order that up first. You also might consider changing the plugs after you take a look... nothing is lifetime and better you know what you've got than something that may have been there awhile. I personally prefer the preventive maint scenario, if I'm working on something I'll fix/replace any other items while I'm there.

 

All good advise. thanks,

Russ

 

Just a quick note about the differences in the upper and lower tensioners: The uppers have little plastic slipper "feet" on them, and these tend to shatter and fall off, leaving the upper chains slack and the chains riding on metal to metal. The upper bodies also tend to crack badly, as well. The lowers have only a "piston" that pushes against the chain guide to keep tension on the lower chains. The bodies of the lowers will also crack, but I cant say as I have seen one fail. What does fail are the guides. The crack and tend to separate. Usually after high mileage has been reached. So, if I had a relatively low mile car, I would do the uppers alone. If I had a high mileage car, I would do it all, and reseal the timing cover etc as well.

 

Ah ha. now we're getting somewhere. that's an explanation I can wrap my head around. thank you!!

Russ