I'm looking at an 1994 XJ12 where the current owner states that the "auto-leveling" suspension was troublesome, and replaced with standard shocks.

Did the 1994 Xj12 have some sort of auto-leveling suspension, and if so is it a concern or advantage that it was replaced with standard shocks? For example, is it any real advantage to have the auto-leveling suspension?

Is is easy to reverse back to stock if the only thing changed were the shocks?

If it did have auto-leveling suspension, was if front and rear, or just rear, and was it hydraulic or pneumatic?

For example, my 1995 Buick Riviera has auto-leveling air shocks in the rear, which are modulated via a level sensing switch and air pump. Many people replace the air shocks with standard shocks as the switch and/or pump eventually quit and most owners see it as an expensive gimmick. But it is easily reversible to stock if desired.


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I have never seen ANY 1994 Jaguar with SLS here in the U.S.

 

Thanks, do you have any information on how it was configured and worked (e.g. rear air shocks?) and if so what one would look for to confirm it has or had the system so I can verify what was done?

And was it even worth having and reliable? Again, my Riviera has it and it works fine, but it is really a gimmick IMHO.

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Hi Al,

Only the rear dampers were equipped with the hydraulic Self-Leveling System (SLS). They were notorious for developing leaks and were outrageously expensive to replace. The resulting owner outcries prompted third-party suppliers to develop kits to convert cars to conventional dampers, which also required new road springs. Jaguar followed suit. Many of these conversions were done relatively early in the life of the cars. Cars that weren't converted by their original owners at the Jaguar dealer were often converted by subsequent owners using aftermarket kits (which were of good quality, as far as I know).

We've heard of owners trying to find original SLS components to keep their cars operating properly, but I don't recall hearing from anyone who wanted to spend the money to return a converted car back to SLS.

If I recall correctly, there were at least three iterations of the system, with most of the changes involving the pump and engine bay components. In '93 the engine-driven mechanical pump was replaced with an electric pump integrated into the valve body (along with the accumulator sphere) and mounted on the right firewall. You can read about the system in the manual at this link:

Jaguar XJ40 Power Hydraulic System Manual

Cheers,

Don

 

Excellent, that is exactly what I needed to know!

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OK, I've read the SLS removal TSB and the hydraulics system document, but although the hydraulics document is very useful it was published in 1992, a year or two before my XJ12 was manufactured. My SLS system was converted to traditional springs & dampers, and so far I haven't yet verified what all was removed but the parts I have in a box seem to match up to the TSB.

From what I can tell on my MY94 (manufactured 1993) XJ12, it appears that the SLS pump and HSMO reservoir & hoses only supported the actual SLS itself, neither power steering nor brake boost, true?

The ABS system is the Teves system with the gas charged ball, so I don't think the SLS system is providing any boost, true?

The power steering on my XJ12 is supported by a dedicated power steering fluid (Dexron ATF) reservoir and pump, but I believe the power steering pump is a dual pump on the XJ12 that pumped both power steering fluid(ATF) on one side, and HSMO for the SLS on the other side.

I know my HSMO reservoir is still in place, and I'm going to assume at this point that the HSMO supply and return hoses are also still in place between the reservoir and pump in place. So I'm wondering if I remove the HSMO reservoir and hoses to the pump, will that damage the pump to run without an HSMO supply on one side?

I'm just looking for confirmation that the entire HSMO pump, valve block, pump and hoses are completely isolated and only supported the SLS system itself on the 1994(1993) XJ12 and if I remove all traces will there be any problems with the pump?

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Hi Al,

I don't know about your XJ12, but on our '93 XJ40 the electric pump and accumulator sphere provided the hydraulic pressure for power brake assistance. They were mounted near the firewall on the right side of the engine as viewed from the driver's seat. If yours are in that same place, you could test to see if they provide brake boost by disconnecting the electrical connector from the pump or pressure switch and checking for any warning lamps on the instrument cluster such as ANTI-LOCK or BRAKE, and also test to see if you have brake boost with the engine running for more than 20 depressions of the brake pedal because in a healthy system you can have boost for nearly 20 depressions even without the engine running (the accumulator sphere stores pressurized fluid to provide this boost even when the engine isn't running).

Cheers,

Don

 

Even my '92 Sovereign had the newer separate braking & suspension/steering boost systems. Your 1994 most definitely has the electrically boosted braking system like my '92. The only difference from your 94's system and my 92's system is the separate reservoirs for Dexron Power Steering and HSMO mineral oil. Mine has one reservoir serving both. My car was converted a long time ago (when it was only a few years old) to the conventional rear suspension. The high-pressure lines to the rear suspension were removed (the line clips are still visible on the undercarriage), but the ride height sensor is still under the car (plug is blanked off), the valve block is still under the hood (pipe outlets were replaced with bleeder screws), and the engine-mounted suspension pump is still in place with the Y-hose to the reservoir and power steering pump. I am still running HSMO for power steering, but will eventually replace it with Dexron. I am just not sure if the old suspension pump is compatible with Dexron, as I don't want to have leaks because of it. If I remove the pump and Y-hose, then I have to find a way to cap off the extra outlet on the HSMO reservoir, and find the correct "steering only" replacement to the Y-hose. Until then, I keep a few bottles of HSMO on hand... I have no leaks so it's not a big deal as of yet.

-Nick