Hello All,

Longtime lurker but new to posting on this forum. 9 months ago I purchased a 2003 XJR with 70k miles and have since put about 15k on it, most of which I've enjoyed. I'm also a perfectionist, so this car keeps me busy!

One of the most pressing items on the list is fixing the handling on this car - it is generally a mess, but I know there was once greatness there. I drive the car ludicrously hard, by the way, but it's handling behavior seems to be worse under normal conditions. Lots of clunks, very skittish, and a general lack of refinement. I have a long list of culprits, primary of which are the CATS shocks - both fronts are leaking and lead me to believe they need to be replaced (yes, I'm aware of the bushings, ball joints, links, etc.). Those of you who have priced CATS replacements know they are outrageously expensive if you can find them, so I am seeking alternatives. I've read every post here and found a lot of confusion, misinformation, and unanswered questions.

Some have offered that you can simply unplug the shocks and replace with regular Bilsteins. Others have warned that doing so will cause ABS and traction control to turn off. Both of these points don't seem correct. What I do know is the following:

1. Unplugging the shocks will trip an obnoxious 'SUSPENSION FAULT' message and amber light that will not go away, so this is not acceptable
2. I reviewed the wiring diagrams for the ADCM module and it is not in any way connected to the traction control or ABS systems of the car, so I believe that prior point to be false or very unlikely
3. Pin 1 of the ADCM module outputs ground to the instrument cluster when a fault is detected, so I'm thinking the cleanest option is to unplug the shocks, replace with standard shocks, and then jump pin 1 to send +5V or +12V to the instrument cluster to block the warning
4. Failing that, I think one could make a custom connector terminator that 'fools' the CATS module into thinking the shock leads are still plugged into CATS shocks - I assume it checks for some basic resistance value - but this may be more involved.

I will try unplugging the shocks, jumping pin 1, and driving around to see what this accomplishes and report back. In the meantime, if there's any other knowledge you can add (or warnings!), I would appreciate it.

After the handling project I'll be tackling some other things to make this car great.

 

I have an 02 and one front shock just went 'open circuit' and tripped the suspension fault light...and set the ride to firm. Motorcars Ltd can get the shocks but they are NOT a common fail item and so far it's taken 3 weeks to get the right Bilstein shock...still with Fedex from TX.
If you jump the leads the light goes out...BUT the system monitors and compares resistance across all 4 shocks so as soon as the car moves...it re-trips. I'm sure their is some way to replace all 4 shocks and disconnect the system...but it's a GOOD system when it works and replacing all 4 shcoks with regular Jag Bilsteins is not that much cheaper than biting the bullet and replacing the cats shocks. At 70K they are probably NOT the problem...but I bet the upper bushings ARE.
Also...BET your froont antiroll bar bushes are done...easy fix....HUGE difference in refinement with new ones, (cheap and easy DIY).

 

I bought an '01 VDP SC with 78,000 miles and had the same kinds of issues with poor handling, clunks and jumpiness. I decided to repalce the Cats shocks with the XJR Bilsteins. I knew I had 1 bad CATS shock and the cost of the 4 new Bilsteins was close to 1 new CATS.

With advise from the Forum (thank you BRUTAL) I unplugged the main harness to the CATS module and the the ABS and Traction work fine and no faults are shown on the display.

I also replaced the ball joints, tie-rod ends, sway bar bushings and links, all 4 front ball joints and the upper shock bushings. The handling is much improved and there are no squeaks, moans, or rattles from the front or rear any more.

The car still does not feel as stable as i think it should be and is feels jumpy over bumps. I plan to repalce the upper and lower control arm bushings in the front suspension. I hope this does the trick because after the bushings there is nothing left in the front end to replace

I would really like to drive an XJR with the CATS suspension to see if I made a good choice with converting the shocks

Ed

 

I have had to replace bushing and such -- but never ball joints. I think I did tie rods on one of the x300 but it was with many more miles than yours.

Running the proper tires is especially important with these cars -- I have never owned any other car that was as particular as to the tires as the x300 - 308 -- especially when you get to the larger sizes in the R.

Now clunk noises are not going to be the tires -- but the handling may very well be. Mine have especially disliked high pressure in the tires

 

My car came with new tires (Goodyear Eagle Response Edge) which I have had rebalanced and I have rotated them around to see if there was any noticable difference. I run them at 31 psi front and 33 rear but Jaguar specs call for 26 and 28.
I don't want to run with pressures that low - touch soft for cornering.

Of all the cars that I have owned the VDP seems to telagraph the any suspension wear back into the cabin

 

RocklandJag

So you unplugged the main harness to the CATS module and you didn't get any warning lights? This allows you to bypass CATS and replace the CATS shocks?

I have a 2000 S type and I'm wondering if I can do the same thing. I just lowered the car with Eibachs. Feels really nice and it actually didn't change the handling characteristics too dramatically, which is what I wanted. I am thinking about replacing the shocks with Bilstein BP8's though because I think it's a matter of time before one of my CATS shocks begins to go.

I replaced the wheels with 18x8 and I'm running Kumho KU19, 245 40 18's. I think that replacing the wheels and tires made a much bigger difference on the handling characteristics than the Eibach Pro Kit Lowering Springs. The car responds much better with the lighter wheels and sportier tires.

 

yes I unplugged the module and have not had any warnign messages or problems with any other system. I installed new Bilsteins about 5K miles ago because one of the front CATS shocks was bad (always in the soft setting) and I figured the others would go over time. I have since read on the forum that the CATS shocks are not high failure items

I sometimes wonder if I would have preferred the ride if I had retained the CATS system?

How does your S type ride with the new wheels and shocks? Is it more nervous than before?

 

Yah, I'm still debating about whether I want to swap out the shocks or not.

From my perspective, the biggest change in handling dynamics came when I changed the wheels and tires.

On the factory 17's, i changed the wheels from Pirelli Zero's to Bridgestone Potenza RE050. Both were 235 55 17's, I think. The sidewalls on the Potenza were pretty hard and the car would jump and skip quiet a bit (Is that what you mean by nervous?) compared to the P-Zeros. Handling on the RE050 was much improved, but, that may only be because they are new tires. The ride was roughest with this setup.

Next I changed to 18x8 Inch Rims (10 Spoke Pattern), much lighter than the factory 17's. I put on Kumho KU19, 245.

I only had this set up a few days before I swapped the springs to Eibach Pro Kit. During the time, the car handled much better and was much more responsive with far better contact on the road. It was far less prone to be being as jumpy.

After changing to the Eibach's with Factory CATS Shocks, the car actually feels softer at slow speeds and in general. It's really hard to describe, I think that in some cases, it is softer and in other cases it feels as if it bouncier, not like jumping but more like oscillating a little more (maybe the bilsteins would help this). At the same time, I also feel more of the road through the steering column. It is much more fun to drive though... not sure if that is psychological or what...

I was thinking about going with the Bilstein B8's, is that the setup you have? Unfortunately, it's on back order. I'm not sure if I'm still going to get them because I am quiet satisfied with my set up now. I'm also considering the B6's because I think I read the pressure was the same. I'm just not sure if one of my CATS shocks will go.

I'd say, the wheels and tires made the biggest difference in improving the feel and characteristics.

 

I installed the OEM sport Bilsteins from the XJR. I am not familiar with the B8's that you mention. Unistalled the sport Bilsteins felt firmer than the 3 good CATS shocks also uninstalled (as they default to firm setting without voltage from the module. I believe if you unplug your CATS module you could see how firm your CATS shocks feel.

My car feels nervous in that small and large road imperfection seems to be felt through the steering wheel and the chasis more than they should. Minor imperfections that my Subaru ignores are felt in the VDP. Maybe the sport Bilsteins are not well not well suited for the springs in the VDP.

Also, the steering sometimes seems darty as if pulled by grooves in the road. I am going to replace the upper and lower control arm bushings next week to see if that helps. I hope so, as I have replaced everything else in the front end already

____________
2001 VDP S/C

 

Hey guys,

Wanted to follow up on this thread and add some more information to the forum. Thanks for all of your responses so far. Here's what I did, and what I learned:

I ended up replacing the front shocks with OEM Bilstein sport shocks (green body tubes) which I found at partsgeek for $130 each. They are slightly firmer than CATS shocks were on firm mode (of course, the CATS shocks were dead by the time I bought the car) which I like, and the front end now tracks bumps much better than before - reduced the skittishness on the front end and spotlighted the fact that the rear end was not really behaving well (and will need new shocks).

I disabled the CATS system by unplugging the CATS module harness (no small feat, located between the bulkhead wall (inside right fender) and the glovebox recess - had to climb in to the car headfirst into the passenger footwell and contort my fingers to get a grab on the connector. This eliminated the dummy light warning and caused no other problems for the car - ABS and ASC still function. I believe this is the right way to do this.

The shock installation was fine, although it should be noted that the upper threaded rod of the shock is a different diameter than the original CATS shock (this was necessary because the CATS shock mounting shaft has a larger bore to allow the wire harness to pass through the center of the shaft). I was in a bit of a pinch, so I stacked some of the included thick washers at the top of the new shock's shaft which allow the shock shaft to seat properly in the metal bushings of the upper shock mount. I am a little worried the washers will distort over time and allow for play between the upper shock mounting nut and the upper shock mouunt, but a few thousand miles of hard driving and things seem to be fine. I torqued the shocks to spec and test drove.

Impressions:
I also replaced the upper shock bushings using the kit from Motorcars. My orange foam bushings did not look great (2003 with 80k miles) but didn't look great either - the new bushings definitely contributed to a more controlled ride.

Handling is always tricky to describe, but I can say that grip has improved significantly due to the new shocks and bushings, as front grip is more tenacious on turn-in and dramatically better when hitting bumps mid-corner. Refinement has improved due to a reduction in judder but I've definitely lost some smoothness that was present before - in general the car feel sharper - I think this is a mixture of the shocks and bushings.

A downside of these repairs is that it places a spotlight on other areas that are lacking - now that the front end action has cleaned up some, the car's busted engine mounts are much more apparent - the taut motion of the front end's new shocks make it clearer that there is a 600-800 lb lug bouncing around in the front end -high frequency undulating bumbs result in a secondary shudder in the front end which I assume is the motor moving. I will try replacing the engine mounts next and report those results.

Steering response has also improved although, again, it clarifies other areas that are lacking - my steering column has a slight vertical shudder (maybe a degree or so) due to play in the broken adjustment mechanism that is apparent when going over rough sections and contributes to a general feeling of instability. No idea how involved that is to fix but would appreciate any advice on that one.

Thanks for the help so far and let me know if you have any questions/thoughts.

 

As a side note, many cars that have a cats system as an option have the harness and all connectors already there. So unplugging the module has no affect on anything else once you swap out shocks. That being said if you dont have cats but have the shock connectors. Youll also have the module connectors. Buy cats shocks and module and youre good to go on the cats suspension

 

Good update.

2nd hand rack if your adjustment is knacked - I doubt ZF or Jaguar will sell bits, an overhaul kit is available though.

 

Thanks, Sean B - to be clear, though, the slop I can feel in the steering is really just coming from play in the tilt feature of the steering column in the interior - the rack seems to be functioning well. My motorized tilt feature is no longer working (despite the motor making noise when adjusted) so I'm presuming the broken worm screw is allowing the play - that's completely separate from the actual rack, right?

 

Yes, the upper/lower column are connected via splines and bolts to the rack. The tilt/reach mechs are attached to the upper column, nothing to do with the rack itself. You'll need the plastic guide replacing on the tilt. I'd suggest calling round breakers/scrap yards, or send an email to the UK jaguar breakers, of which there are dozens if no joy your side of the pond. It seems to be a common failure point.

removal process + info described here,

https://www.jaguarforums.com/forum/s...ad.php?t=42662

 

I just bought my wife a 2003 S-type R SC as a daily driver for in town driving. It sounds like the rear CATS have went out on both sides. Two questions - can I replace the CATS with Bilstein B4/B8 and where/how do I disconnect the CATS so that I do not see the warning message in the display? This is just a daily driver with 127K on it, and as such she wants the most inexpensive way out. Help? Ideas? Any replies would be appreciated.