got some questions about the SLS system in the "88" XJ40. after examining the system, I discovered that the fluid level was way low. I refilled the mineral fluid system and took it for a test run. the front suspension feels great, but the rear feels "bouncy". I checked the rear suspension for leaks and found none. I parked the car on a nice, clean pad overnight to see if I could identify any leaks anywhere in the system. 4th day now.... no leaks and the mineral fluid levels are still up. does this system require any "bleeding" sort of procedures? my first thought is that the rear suspension was dry too long and may have some kind of mechanical failure within. any thoughts?

 

The SLS is borrowed and very similar to Citroens Hydropnumatic suspension system.

The bouncing you are felling is due to the accumulator sphere having become discharged. This is a green ball shaped object you will find somewhere around the back axle, it is half filled with Argon Gas and the other half is filled with suspension fluid (Mineral Oil, known in the Citroen world as LHM). Replaceing the cylinder should be fairly simple, firstly you would need to relieve the pressure of the oil from it (this bit I'm a little unclear on as Citroens have a suspension setting to dissipate the pressure from the system) The manual states to raise the rear wheels off the ground and then pump the brake pedal until it goes hard, this should then alieviate the pressure in the system. Now you will need to unscrew the sphere, on citroens there is a special tool, which looks like a very heavy duty filter wrench, and I can attest to the fact that it's unlikrly to come undone without such a tool. But if you suceed, it's just a case of swapping the sphere over with a new one. Don't panic over pricing just yet, the sphere should have some markings in it which give the psi of the gas within, this is exactly the same sphere and fluid as used in many citroen cars, and many citroen specialist parts handlers will usually have a stock of 'aftermarket' spheres that are not only a lot lot cheaper than Citroen and Jag prices, but also of equal quality to the original part.

Putting the new sphere in is very easy, just spin it on and tighten it by hand as tight as you can get it. That's it job done.

I could even suggest one or two if you so require (both UK Based, one in NE and one in SW).

P.S I have Owned and maintained a number of Citroens with Hydropnumatic suspension and the CX remains to this day one of my all time favourite cars.

 

^^^ Good stuff, Ill check that out. is there a way to salvage the existing sphere? I saw people selling "rebuilt" ones online

 

The sphere can be rebuilt, but this would have to be done by a specialist as it involves removing the valve from within the sphere and recharging the sphere with argon to about 360psi, plus the cost of 'repairing' or a reconditioned sphere is always much much more than the cost of a new one and they don't last anywhere near as long as a new one because you can't replace the rubber diaphragm inside the sphere and it is this that is the main reason for the spheres losing their pressure. (This is from the experience of many Citroen owners).

The last time a bought a set of spheres was about 4 years ago and I was paying back then £17 each new (about $25) for Aftermarket, Citroen OEM were £70 each new (about $95), Reconditioned were about £35 (about $50). God knows what Jag's price is, but the manual seems to discourage one from anything but replacing it with normal coil springs! (Methinks some licensing issues with Citroen may be responsible for that).

 

So in my search for a replacement accumulator, I've raised a couple of more questions about this suspension system. 1st; is the ride better or worse just installing the conversion kit, and 2nd; would "spongy" brake pedal point to this accumulator as well? on the "spongy" brake pedal, its kinda strange. I can pump the brakes a few times (while driving) and get the pressure built up enough to brake at the normal compressed brake pedal location. if I don't pump them, the brakes will start to engage at the normal position, but push a tiny bit harder and the pedal will sink near to the floor, but will engage fully at this point. I'm going to replace all the rotors, pads and fluid tomorrow, so they will get bled properly at that time. hopefully this will correct the spongy brake issue. at the moment, the dot4 fluid is full and there are no leaks in the brake system.

 

On wether the ride quality is improved or worsened with the conversion kit I cannot comment, as all my XJ40's had 'normal' springing, but were certinately comfortable although not a patch on the CX Citroen.

I would hazard a guess that the ride would be slightly less pliant, but again the main point of the SLS was to maintain ride height regardless of weight, so it may well be that the ride is the same, especially as the SLS doesn't use the full hydopnumatic system, rather the struts feed into the accumulator sphere which increases the rear suspension pressure according to the ride height sensors. This system is also linked to the braking system and adjusts brake force equally to compensate for increased axle load. The symptom you describe with the brake pedal is exactly what happens when the accumulator sphere has lost it's gas pressure. The system is also to a large extent self bleeding as the LHM is constantly being circulated through the reservoir.

 

Hi,

I'm one who had both the SLS and brake system converted due to the consistency of having problems after repairing the original equipment.

The SLS strut seals kept popping, even with new sets I would have problems within a year or two. At the time the replacements were really expensive and I had rotten luck with them, so converted to a traditional shock system and very glad I did, that has been over 11 years ago and there was no difference in ride quality.

In regard to your description of your brake system, sounds all too familiar. In my case the brake accumulator and various connections kept supplying me with a fresh flow of hydraulic fluid under the carpet and padding in the cabin. There are conversion kits available if you search the web. If you can't find one, email me , or post up again.

I am one who loves the idea of everything being original and operating as intended, then again I like to drive the car and not have it cost me a fortune to keep it on the road.

Good Luck

Hope you have success with whatever decision you make.

Rob Evenson
Mobile, AL, USA
89 XJ40, 3.6L, 123K

 

You need to download the publication S-73 XJ40 power hydraulics that I uploaded a few years ago to the sticky section.

Also read the TSB for deleting the rear SLS.

This info is what you need.

bob gauff

 

Thanks for the input guys, Looks like Ill be putting the conversion kit in. Is it an OEM part assy, or are there aftermarket vendors?

 

Look on the last page of the PDF that Bob provided and you will see referenced the part number JLM 11698, here's a google search result page:

https://www.google.com/webhp?source=...w=1280&bih=909

Good luck

Rob Evenson
Mobile, AL, USA

 

UPDATE!! - Yesterday I got to looking over the brake system to try and rule out any other issues that could be causing my spongy brake pedals. I had already bled the system and didnt get it fixed like that, so I did some "tinkering" with the caliper assemblies to see if they were functioning properly. in doing so, I discovered that there was a good amount of sediment in the caliper piston housing. I rebuilt all caliper assemblies to make sure no debris were present. after putting them back in, the problem was solved! the brakes now work GREAT, they feel like they're brand new! I still have the anti-lock failure and low brake pressure lights on in the dash, but the system is functioning great! now to get those old SLS struts out of there...

 

Does anybody have detailed information about this SLS? It's diagrams, images? working strategy? My car Raises and lowers after starting and then looks normal, not too high or low. However, when I press the brake, the red warning light appears. I also think, that there's an anti-lock warning light missing. Should it be in the left row 3rd or 4th from the bottom? I have one "spot" missing there. I don't want to get rid of the SLS. I want to fix the car So it will be as good as possible.

 

I was able to find some diagrams by looking online thru google. What year is your Jag? My initial thought is that since your SLS is actually functioning, that your problem might not be in the SLS fluid system, rather in your brake system.

 

That might be possible. I've found some info about Brake and ABS lamps going on, when the SLS is failing. Car is not insured, therefore I can't go on the road with it and I can't check the ABS system. As yet Another problem is the way it is acting on the road- it's really stiff, like a wheelbarrow. Range rover L322 also does crazy thing with the suspension when ABS goes down. Is it possible to connect to this vehicle with WDS or IDS? My car is 1993 XJ 4.0

 

I do not agree with this. Your writing kept me on a false track for some time. Have you read the Hydraulic Manual ?
The sphere has the role of accumulating energy for the brakes and nothing else. The bouncing is a result of the shocks internal to the struts having failed. So it seems there is nothing one can do regarding such bouncing than replacing the struts (or replacing with conventional shocks). I like to be proven wrong. I have a late 93 model. As seen in the manual there are different setups for early and late XJ40s. But that accumulator is concerned with brake servo power.
On the later XJ40s such an accumulator is found only on the ABS brake equipment where that system is independent of the SLS.

 

***Update***

during an unrelated A/C refill, I was tinkering with fuses and relays correlating with the SLS system..... to my surprise, when I removed the SLS fuse and relay and plugged them back in, up rose my rear end! now, the SLS operation is intermittent and very random, often cutting in and out several times during a drive. sometimes it doesnt work at all and sometimes it will work the whole ride! this must be an electrical problem, being as mechanical problems dont just fix their selves. maybe a sticky relay, maybe a short, a sensor? I still plan on deleting the SLS from this ride, but if I can get it going I can deal with some expensive cosmetics that are driving me nuts first!

 

Hi, sorry but I'm not very good at these forum things - too old I guess!
Could you please tell me how to get to the sticky section or Bob, possible email me a PDF.
My just purchased 87 XJ40 has only done 20,000 miles but I've got a good clonk in the back which sounds like a shock.

Thanks

 

It seems often relays can develop solder joint issues, it can sometimes be sufficient to tap on a relay for it to come active. It could be the relay you worked on have some bad contact at some joint and works irregularily. From the issues I have come across often the levelling works but the suspension part have seized/frozen up, causing a stiff rear end.

 

It seems to be effecting the system as a whole, as I will get great working suspension (feels great, no bounce or anything) and sometimes I will bounce the rear end all the way down the freeway! I have noticed that its not rising when I start the car up now, but the suspension is still very random. It could also be the beginnings of the rear suspension failure. I will still be deleting the SLS, but Ive moved that operation further back and moved tires/wheels/rotors/brakes/boots/front end service to the front. one part at a time, this will take about a year to get fully restored. but.... getting there. Im to the big dollar items now, so fewer and further between are the fixes.

 

1991 vanden plas thanks new to site sorry if i posted wrong.
The rear sls raises about a minute after car is started to the top clicks a few times and then lowers all the way back down and is very bouncy the mineral fluid was low a qt filled that even tried the rear level sensor with no luck same thing please if you have a idea it would be greatly appreciated Joe njoeandjen@comcast.net Thanks in advance!!