Hi there,

I'm relatively new here, and I've been reading all that I can about XJ40s. My great aunt has a '92 Sovereign with 50k miles, which she bought in 1994. She's looking to downsize her number of cars (recently selling her 1976 Rolls-Royce Silver Shadow to my mom) and I've always been fond of her Diamond Blue XJ6. So I'm researching before I make the move.

Her car was originally fitted with the SLS system, and I'm not sure if it's still there or not. She takes very good care of her vehicles, and I wouldn't doubt if it was still there in good working order.

Maybe I'm belt-and-suspenders about keeping things original and working properly, but I don't think I've found one person here talking about keeping the SLS suspension. I know Jaguar put out a TSB about removing the SLS due to the high cost of parts and labor for the SLS system.

My current car, an Oldsmobile Regency, has a pneumatic ride-leveling suspension and I happen to love it. Loading the back seat or trunk, and the car never droops or sags in the rear. Remove the weight, and it's right back where it was. Granted, it's a much simpler system...

Does the XJ40's SLS use the hydraulic fluid as a damping fluid along with accumulators, such as the hydro-pneumatic systems fitted to Rolls Royce and Citroen cars? Or are the rear shocks typical gas-charged units that extend and contract (to correct the ride height) when hydraulic pressure is applied? In other words, does an SLS-equipped XJ40 ride better than a converted car with typical shock/spring setup?

Thanks,
Nick

 

Hi Nick:
First let me say that it's great to have you on board the forum. You've already contributed a lot! Second, let me say that if you don't buy your great aunt's Jag, I will! And I'm being quite serious.

I have never ridden in a car with the SLS, so I cannot answer your question. But I do have another question for you. My understanding is that the American spec cars (and perhaps those worldwide) changed over to the standard set up in late 1990 or early '91. Indeed my '91 has the conventional suspension and has always done. Are you sure the '92 has SLS?

Cheers,
Scott

 

Hello Nick,
Welcome. I'm not sure if I can be of much help, but I'd like to comment. My 92 Sovereign had the SLS on it. I dont know when it was removed, but the connecting rod ball sockets and electrical connectors are still left on the control arms. And there was the (to me anyway) very odd 3-way hydraulic pressure line in the engine bay. I cant say better- or -not but that I've never had or heard any complaints about the ride quality even now with it past 172000 miles. If you can, I would highly recommend owning this vehicle. Mine still makes me smile after 7 years. By the way, I agree 100% that if its working, leave it in there. Why fix it?
Regards, Jerry

 

Hello,

From what I've read, it seems the Sovereign here in the USA had the SLS system as Standard from at least 1990 on to 1993. For MY 1994, it was deleted on all cars, and traditional springs/shocks were used. The Jaguar SLS delete kit basically converts the rear suspension to 1994 MY specifications.

I purchased a 1992 Owner's Manual to get to know the features and maintenance schedule for the car, and it explains the fluid specifications for the Self Leveling Suspension, including a warning about only using HSMO for both the power steering and suspension system.

I know that the power hydraulic vacuum brake booster was removed for the 1990 MY in favor of the traditional vacuum booster, simplifying the power hydraulic system on these cars, and because of that, I'm glad this car is a 1992.

Thanks,
Nick

 

Nick,

Buy the car and if the SLS is installed and operational use it until it goes south on you, then replace with conventional shocks, especially if you will use the vehicle frequently.

I have an 89 and mine had the SLS, and I replaced the SLS struts twice before throwing in the towel to have the conversion done. I use mine as a daily driver and the cost to maintain is extensive if used for daily.

Some people have kept the original system, but I think you should query them as to the amount of use their vehicle actually gets, then make a decision about the conversion.

I too like to have all original, however the brake and SLS systems on these vehicles were simply not designed well for rigorous use, thus you find many examples of conversion for both systems.

BTW, the fluid used for mine was the Castrol Mineral Oil which was green in color, and permanently ruins a persons shoes when the accumulator fails and runs down the brake.

Good luck

(buy the car )

 

My 88 XJ40 (108K on it) still has the original system in it and the fide is fabulous, so far the only problem issome leakage that I've traced to the hoses that connect the reservoir to the system.

Yes the Castrol Mineral Oil does ruin any clothing orleather it gets on,

I only drive my Jagin the summer so it is not a daily driver (northern MN winter is no place for aJag) but I do like things as original asI can reasonably get them on my cars (but I am going to put in a better stereo system I need good music when I'm driving around)

Any Jag in good shape is fun to own.

 

Thanks for the replies!

I was looking to find someone (just one!) who had the SLS system still in place. Of course, seepage and small leakage is to be expected, but hoses and lines can be replaced. I was worried about the actual leveling shocks/rams leaking.

If the car has the system fitted, the first things I'd do would be to flush the system with brand new fluid. My aunt takes very good care of her cars, but I'd like to get all the fluids (transmission, SLS, brake, differential) changed so I know exactly how old they are.

I love the satisfaction of solving problems, and enjoy electrical work, so an XJ40 seems perfect to me! Also, here in Rhode Island, we do occasionally have bad winters, but I'd definitely purchase another set of OEM wheels and mount true studdable snow tires. I don't think the '92 Sovereigns came with the Power-lok rear end, but I'd definitely look at fitting heated seat kits and a remote starter.

Thanks,
Nick

 

The SLS hydraulics is not part of the actual suspension travel.
It merely deals with levelling, setting the height of the suspension.
The SLS shocks are dual function. They have one independent subsection that control a base height via hydraulic oil. That height will remain stiff/constant throughout any travel over bumps and irregularities. The other totally independent part of the unit is a conventional gas damper that has nothing to do with the SLS hydraulics. This is where the suspension travel occurs. And this part is most often then one that fails when it comes to experiencing a stiff suspension.

So if you replace the SLS dampers with a conversion kit you get the same gas damper function as before, only that the previous levelling is now a fixed height that is more sensitive to load variations. But the advantage of the conversion is that the car is no longer sensitive to a failing levelling system, the case where the car does not ride with the rear wheels at a proper base height.

One drawback with a converted vehicle is if you load lots of passengers or have a trailer coupling and run heavy loads on it there is no longer a mechanism to compensate and keep the car level. In that case your converted car could sag a bit at the rear under load.

It *could" be the SLS is experienced as slightly softer/more comfortable because the conversion kits contain a bit stiffer road springs since they need to compensate for the lack of SLS and not sag as easily. Yes, any difference in comfort will be due to this.

 

I have the rare 1990 VP Majestic , was the SLS standard on those or do they have the normal suspension. I want to fix it right before I sell it. Seeing as they only hand made 527 of these, I don't want to take away from the value of it.

 

Hi JimmyHands,

Welcome to the Jaguar Forums! You certainly do own a rare car, but I suspect that its value would actually be higher if the SLS has already been converted (and many of the XJ40s were convereted by the dealer early in their history). Others will have to tell you exactly how to check to see if your car has been converted, but in the meantime, since we're a friendly bunch around here, please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an introduction so we can give you a proper welcome and learn something about you and your Jag.

Cheers,

Don

 

I have a troublesome sls on my 1991 Jaguar xj6 sovereign. I’m trying to decide if I can keep it also.

 

Its a deterrent that keeps new owners away. SLS cars are not desirable, and dont command more money or authenticity. It was a mistake that hasnt been improved on for over 30 years. If you are able to throw money and time at it, good for you, and the car. But don’t expect it to carry your nose up in the air because of it.