Hi all,
The other day I was driving on the highway and hit a separation in the asphalt, while turning slightly right going about 70mph - it was very jarring. This separation was straight across the lane (some sort of road construction is my guess) so all 4 wheels got the same type of impact. Immediately after, I noticed the suspension was much stiffer - almost as though during the turn, the CATS stiffened, I hit the separation in the asphalt, and the CATS remained stiff...

A couple days later and they are still firm, without having reverted back to "comfort" mode since. Ride height is normal, no suspension fault codes, etc. Everything electronically seems to be normal. Any ideas what may be happening? I've read that there are 3 accelerometers on the vehicle that feed info to the CATS module. Is it possible one of these has been dislodged? Any way to "reboot" the CATS system?

Thanks for your feedback!

 

Initially you have 2 options I know of. One is to check your connectors on the top on your front shocks to be sure they are still connected or the connector isn't broken (most likely). Second, a hard reset (remove the battery cables from each terminal and hold them together for about a minute to bleed off any excess power). Let them sit a few minutes and reapply. Note that you'll loose all your memory settings from the seats and mirrors, to your radio.
If neither of them apply or work, you may need new shocks, even though it may be one that's bad. I recommend replacing in pairs if needed.

 

The workshop manual recommends first checking the fuse #1 in the small fuse box in the engine compartment.

 

Thanks for your response, Highhorse. Had the car in the driveway earlier today double checking my tire pressures and checked the connectors - both are strongly seated and normal. I also pushed down on both sides of the front of the car to check shock behavior. If it matters, the car was running and in Park. I pressed down with most of my weight and the shock compressed and slowly came back to normal height. Was not bouncy at all and seemed very controlled. Now I’m not totally certain of the proper shock behavior (I’ve never needed to test it), but any thoughts on this?

If this seems normal, I’ll give the hard reset a go tomorrow and hope that’s it.

Appreciate it!

 

Check what MS said also....

 

I believe that if you have the jaguar software, you can check if there's a fault in the cats suspension, eg a ground somewhere it shouldn't be.
Might be a mention of this in the workshop manual?

 

In the process of replacing the fuel pumps in my '02 XJR I disconnected the central accelerometer at the base of the fuel tank (just ahead of the spare tire). I forgot to reconnect it upon reassembly. All of the shocks were at full firm on the subsequent test drive. Not clear if you checked that connector....

 

Checked fuse #1 in the small fuse box in the engine compartment and it looked good. Just completed the reset and took a test drive - no difference, unfortunately. I did notice when I parked back in the garage the my right side was sitting MUCH lower than I had seen before. I attached some photos. Does this look like a blown shock or could it be CATS system related? The funny this is, it didn't look like this before the reset.

Front passenger side after test drive (after reset)

Front driver side after test drive (after reset)

After test drive (after reset)

After test drive (after reset)

 

Also tried to take some photos of the underside, of it might help. First photo is the side that is sitting lower (passenger) second photo is the driver’s side.

Doesn't seem to be any leaking fluid on the shocks or on the garage floor...


Passenger side



Drivers side

 

Have you checked your sway bar to see if the bushings may have given way?

GOODYEARS....aaahhhhhhh....kaka. I had those on mine for about 8 months and dump trucked them...garbage tire. I got tired of being sideways in an aggressive turn on moist roads. Went back to the reliable Michelin Pilot Super Sports...much better traction.

 

Pretty sure that one is shot, when mine went south, they did not show any leaking.

I don't have CATS on my XJ8, but the fronts gave way after some work on the lift, guess the decompression was the final shot.
I had noticed a slight drop on one side some time before, when the 2nd shock gave way, it dropped completely.
And it felt rock-hard on my limping way home.

Finally, any electronic failure in the system gives the SUSPENSION FAILURE warning in the dash, an other indication you have a mechanical issue and not electronic.

https://www.jaguarforums.com/forum/x...d-inch-176869/

 

You need to replace the shock absorber (the good practice is to replace both sides, even though the other side seems good). The jag shock absorbers are filled with gas under pressure which works together with the coil springs to keep the ride height. When the gas leaks out, the spring by itself cannot keep the the ride height thus the low sitting.

 

I just replaced all the sway bar bushings and end links 10 days ago - so I know those are all good. But based on the comments here, the car being up on the lift for that work could have influenced the failure of the shock. Still seemed totally fine until I hit that bump on the highway a few days ago though, but that must have been the last straw.

HAHA funny you say that - the Goodyears were basically brand new when I bought the car from the previous owner and I still looked into swapping them for the factory P Zeros or the Michelins you mention. Alas, I figured I'd ride out the Goodyears for a bit, but I've been trying to get the ride tightened up lately and that may be the next step after I get these shocks sorted.

 

Last year I had the front of my car on axle stands for a few months, with the front wheels removed and the suspension fully extended. Guess what - both front shocks failed (the front sat like a lowered race car) after the first test drive when I finished the work I was doing. So, if you are going to keep the car jacked up, do not leave the suspension fully extended for any prolonged period of time.

 

That's great info MS - thank you. The longest amount of time it was on the lift was 3-4 hours, so they must have been close to failure to begin with at that point. I have read that CATS shocks rarely fail, but I suppose I'm one of the unlucky ones...

 

Alright folks - just went into the garage and couldn't help but notice the car didn't seem lopsided in the front anymore. I got a closer look and the front end had seemingly leveled overnight. I've attached a reminder photo of what the shock looked like after test driving yesterday, and then a photo from this morning after sitting overnight. I really don't know enough about the behavior of these CATS shocks, so I'm trying to get as much info as possible before I take next steps and get the opinion of a mechanic.

Is it typical for a worn shock to slowly raise back to normal height after being compressed for a period of time? Is it possible the shock may have enough gas left to slowly return the vehicle to normal height when sitting still, but not enough to keep it level under the stress of driving? Sorry for the ignorance here, but this one seems strange to me.


Front passenger after test drive

Front passenger after sitting overnight

Side by side

 

I can totally imagine that, my old shocks would need some 2 min without load to decompress, but they still did.
I can see them decompress overnight on the car, but one bump will probably compress them again like happened to you yesterday.

New CATS shocks all around are not cheap, alternatively you can replace them with the non-CATS version, and disconnect the circuit to prevent the suspension warning on the dash.
We did that with 2 cars here recently (an XJR and a Daimler), with 2 happy owners ever since.

 

Really appreciate your insight here, Eric. Deep down, I'd love to stick with the CATS to keep things original, but I know the cost would be really hard to justify for me.

A few questions for you...

For the XJR, did you replace with the Bilstein sports? (https://www.rockauto.com/en/moreinfo...1440765&jsn=14)

Any thoughts on how the ride will differ vs. CATS? I really don't do any track driving or hard cornering. The XJR is my daily.

Any idea what a rough estimate would be for a shop to do the non-CATS conversion?

Thanks!

 

I know what you mean there, but for the costs involved (some 3 times the price), I doubt I should keep CATS.
It is a rather simple and crude system, nothing advanced like more modern systems, and I do not really see the benefits for a daily user.
That said, there surely is some benefit, depends a lot on riding style I guess.
But that is all a personal take ....

For your info, I did some replacements:
1. My own Vanden Plas, replaced Bilstein comfort for Bilstein comfort all around.
No change in comfort / ride other than solving the broken shock issues, soft as intended, bit wobbling in certain conditions if you look for it.

2. A Daimler of a friend, replaced Bilstein CATS comfort for Bilstein comfort all around.
Frankly, did not notice any difference on normal (test) drive, other than a much harsher drive if you pull a connector (default HARD mode).
I guess it might take away some of the wobbling mentioned above if CATS supports.
Owner is very happy.

3. An XJR of a friend, replaced Bilstein CATS sport for Bilstein sport all around.
Here I did not really notice the difference, but coming from my VDP, I might be the wrong person to notice .
Owner is super happy, but is not that corner burner.

I also have a XK8 coupe fitted with Bilstein CATS comfort.
I think the initial set up is a bit stiffer for the XK8 than my VDP, but still comfort orientated, much in the same way as my Vanden Plas.
I drive this car a bit harder (sometimes), it is a bit harder in the suspension (but also has 19" wheels), but nothing too different.

All that said, if you are not a corner burner, I personally should opt for a non CATS set.
Good thing, it is always reversible ...

I have no idea on the shop costs there, but if you have a lift and all that, I estimate a shop does the front swap within 1 hour, the rear in less than 3, and disconnecting the module in 15 min.
A good morning work, rough estimate though, as other issues might arise.

 

Thanks again, Eric, for this information. First appointment I could get at the mechanic was Monday afternoon so I'll see what they say. Will be a few days before I come back to update the thread with their findings! I appreciate everyone's input!