I have a 1998 XJ8 that has a tappet like noise coming from the timing chain area. I had a non jaguar guy look into it and he did some research and thinks it may be the timing chain and guides. I was told that it had updated rails etc. done under warranty. He thinks some of the upgrades were of poor quality and Jaguar came out with subsequent upgrades.
The symptoms are the ticking seems to come and go. I have noticed it more after the car warms up. When I rev up the engine there is a noticable noise like an actualtor openning and then the noise dissappears. After idling for a few minutes the ticking noise slowly comes back. If you gradually raise the rpm it does not go away rather a quick snap of the throttle seems to do the trick. I would guess it has something to do with oil pressure but that is just a guess. I was told by the fellow that sold me the car it was the automatic valve timing adjuster sticking but I have no idea how that works. Can anyone enlighten me on this issue? Also if it is the chains and guides is it worth doing? The car has about 45,000 miles on it.

 

The Variable Valve Timing (VVT) unit will indeed produce a clicking sound that is normal operation. Unusual operation is usually attributed to low oil pressure on higher mileage engines. Solution is often to jump up 10 on the weight of the oil used.

If you do not have documentation or visual inspection of the plastic tensioners you really . . . really need to pull a valve cover to verify. Tensioners can and have killed an engine. Follow this link for more information:

https://www.jaguarforums.com/forum/s...ad.php?t=23870

 

You can read all about the Jaguar V8 on this website. Some fascinating stuff that explains why the cam tensioners are so troublesome, (and a few other things too !!).

http://www.jagweb.com/aj6eng/v8_performance.php

I would not worry about the Nikasil issue; after all, your engine has managed 12 years without the linings failing, and if they haven't gone now, they wont ever go, as the sulphur in petrol that caused the problem has now been removed.

 

Thanks for the info. Is there something with the VVT that could stick because of sludge or other residue that could cause this? I was thinking of using a good oil flush to try and remove the varnish.

 

Is there any reason to think that the engine had overheated or gone 30k miles without oil change? If not there really should not be sludge at 45k miles.

Continued oil changes with good oil at regular intervals should flush any concerns.

You still might have to go to 40 weight oil.

 

No indication of overheating. The reason why I thought it may be sludge is the owner was 92 years old when they pulled his drivers license. At that point he had the car for 8 years and accumulated 35,000 miles. I am guessing he wasn't what one would consider a lead foot. I visualize short trips in city driving for most of its life.

 

I had upper tensioners changed with new steel ones and I still have this same sound as I did 8,000 miles ago before the upper tensioners were replaced at 34,500 miles. Is this a timing chain sound that is heard or could this be some thing else, a VVT that takes a second to get oil to it. What is this sound???

Video & sound link of the upper right side by the VVT
http://www.youtube.com/watch?v=RLWGZVF4OrM
Under the front of the car
http://www.youtube.com/watch?v=mLynasgUpuc