my 08 xj8l does not take bumps any way except hard; rides great until you find the rough road bumps ??? IDEAS

 

The ride of these cars is not one of Jaguar's best efforts, and is not helped by large wheels and low profile tyres. What size do you have on ? However, there may be a fault code still recorded that is causing it not to switch the shocks to Soft. You need to check for fault codes. May I assume there is nothing on the dash display ? My own car can be quite harsh on the sharp-edged bumps, it is OK on most others. Of course if our UK roads were like those in Germany I wouldn't be complaining !

 

I think there is too much made of this CATS suspension.
My 08 XJ6 with 19" wheels feels every bump. Sure not as much as my small Honda Insight, but probably equivalent to my Honda Elysion MPV.

We have lots of speed bumps here. Certain ones the Jag floats over. Other ones the Honda floats over better. Our City Council just has no sense of consistency.

But Oh...The Luxury! The Quiet! The Pink Floyd! (sorry about the last one, which I played in my Series 2 when it was current)

Anecdote: By chance I saw an XJR (X350 or X358) at a dealer. I never drove it nor was it my style. But he unsolicited said to me "Don't drive it over railway lines".

 

I think people expect too much of large Jag saloons. True the Jaguar is a luxury car, but it's a sports-saloon/sports-sedan, not an out-and-out limo; it's not purely a motorway/interstate 'barge'. Nor is suited to rough roads ie tracks, any more than say a Mazda MX5, or an MG sports car.

Now, it depends what you mean by bumps. Rough surfaces do come through to the car if you have low profile tyres, ​​​​​​such as on 20" or 19" wheels. 18" are better and better still 17" which was an early but apparently unpopular option on the X350; I think they were standard on the Daimler version. The low profile thing is a pure 'fad' and is only advantageous to those who want to indulge in maximum acceleration in a straight line. They don't give better lateral road holding, indeed there are arguments that slightly narrower and deeper sidewall tyres are better for that.

If you are talking about bigger bumps then it's possible that your dampers (they are controlled entirely automatically by the CATS system) are permanently in the 'hard' setting. You can test for this by disconnecting the CATS lead to the top of one (only needs to be one) of the dampers; that's the lead to the top of a suspension unit. The ones under the bonnet are easily the best to get at. Disconnecting it will make the whole CATS system, ie all four dampers, go into the default 'always hard' mode. Then try driving the car. If there's no difference then the CATS was in permanent hard, fault, mode. If on the other hand the ride is obviously harder (and you will know it) then the CATS was operating just fine.