I don’t think there’s much difference if the timing guides have been updated on 4.0.

 

The 4.0L engines suffered from the Nikasil linings, that said, if they are still running and have been well maintained with the upgraded tensioners and water pumps then there is not much to worry about l

 

I've got at least one for sale here, but the steering wheel is on the correct side.

There are several youtubes such as Back to the Garage, where you can learn about the X100. Nikasil liners were only fitted to earlier engines.

Good luck with your search and keep us posted.

 

Nikasil liners were only fitted to earlier engines.

Which is what the 4.0L is, anything after 2000 did not have it.

 

There's an actual serial number and date buried somewhere or other, as the changover was in mid - 4.0 production. Seems to be a non-issue with modern petrol grades, anyway.

 

Hey guys,

I’ve been wondering if I should get a 4.0 or a 4.2 in the XK8. I’ve heard that the 4.2 is more reliable, but I’m not sure if the 4.0 is that of a nightmare that people have said about it. So far I hardly ever see any 4.2s for sale in the websites, only just 4.0s. Maybe that’s why they’re for sale often, due to it being unreliable. I’m not sure

I went through this very dilemma myself last year. I was erring toward a 4.2 as they are supposed to have had all the issues ironed out, but found there was a lot better choice of cars in 4.0 guise, so that's what I ended up with. Most of the 4.0l's problems can be eliminated with the use of uprated components (if they haven't been already), and as has been said, the Nikasil liners were only fitted to pre 2001 cars, and were only a problem where high sulphur content fuels were used. They're not an issue with modern low sulphur fuel.
Here's a couple of links that may help,

http://www.jagutek.co.uk/timing-tensioner.php

XK8 / XKR (X100) 1996-2006 Buying Guide

It’s hard to believe that the XK8 has been around for almost 25 years. Introduced in March 1996 and on sale from October that year, it was Jaguars first eight cylinder model since the Daimler 250 which ceased production in 1969.

www.autoreservejaguar.com

Regards,
OW

 

4.0 engines also have/had throttle body position sensor failures, they can be repaired, hopefully with upgraded sensors.

Also, and most important of all, the 4.2 has more power

 

4.0 engines also have/had throttle body position sensor failures, they can be repaired, hopefully with upgraded sensors.

Also, and most important of all, the 4.2 has more power

Only about 4 bhp, but every little helps