I’ve spent some time searching the forum to help me diagnose and repair the SLS system on my 85 wagon. I've found some significant debate on the causes and solutions for the w123 wagon SLS system, and am having a difficult time diagnosing my problem.

I’ve found disagreement on the role of springs:

Douglas.Sherida’s rebuild:
http://www.peachparts.com/shopforum/showthread.php?t=195914&highlight=w123+wagon+sls
But maybe springs don’t carry unloaded weight?:
http://www.peachparts.com/shopforum/showthread.php?t=219461&highlight=w123+wagon+sls

And is a jarring/rough ride a telltale sign of bad accumulators?

(post 10 in the link below)
http://www.peachparts.com/shopforum/showthread.php?t=88461&highlight=w123+wagon+sls

Or can a bad accumulator provide a bouncy ride? How can it produce both?
http://www.schumanautomotive.com/forums/showthread.php?t=2226

Here’s what I’m faced with:

Symptoms:
- A harsh ride. I can feel every bump and minor pothole.
- Sagging while parked for several hours, but rises up when motor starts.
- The kicker: I just replaced both rear half-shafts (thank you Jeremy5848 and dmorrison for superb write-ups). After replacing them, I started the car, the rear end rose, and a high-pitched squealing came from the rear end. Sure enough, it was the SLS system screaming - it kept pumping and pumping. Even before replacing the half-shafts, I had a hunch that the boots on the old ones were torn because the PO set the ride height too high. This confirmed it for me - fortunately, the new half-shafts were strong enough to prevent the SLS from rising any further (to the previously hyperextended height), and tearing the new boots (kudos to CVJ). But the SLS system was straining and screaming.

Actions:
- I put the rear end on ramps and disconnected the SLS valve linkage from the rear stabilizer bar. With the engine running, I got under the car and manually raised and lowered the SLS valve - no problem. The car rose and fell perfectly. Afraid to tear the boots on my new half-shafts, I tried to lengthen the linkage to lower the max height.

- This is where the SLS system exhibited a mind of its own. I adjusted the linkage, started the car, and nothing happened. I turned it 1/4 of a turn, fired it up, and it raised to max height with the SLS screaming at me. I moved 1/4 in the opposite direction, and nothing would happen. I played with this at least 15-20 times, and never got the same result. It was always all-out (max height) or nothing, like a runaway SLS valve.

- I got under the car and noticed that the valve would stick slightly below the “normal” position. I forced the valve past the sticky point, and the rear end would raise to max height. Only once or twice did I get the wagon to automatically raise to a reasonable height where the SLS valve properly stopped, but it could not be replicated. In the end, I decided to disengage the SLS system (removed the linkage and fully lowered the valve) until I can at least provide a temporary fix. Consequently, the wagon is currently a low-rider.

So even after researching through the forums, I am still unsure of a proper diagnosis. Is a sticky valve indicative of leaking O-rings? (the valve does NOT stick when the engine is off, presumably due to an absence of hydraulic pressure...). Is a sagging rear end indicative of leaking O-rings, a leak in hydraulic hoses, or bad springs? Is a firm, jarring ride indicative of bad springs, or just the SLS being disconnected? Come to think of it, even when the SLS was engaged before I replaced the half-shafts, the ride was still somewhat jarring, as opposed to the incredibly smooth ride that those with fully-functioning SLS have reported.

I really hope it’s a rebuild issue ($5 o-ring kits still available), and not accumulators...

Any help is appreciated!

__________________
-1985 300TD - 324k mi on chassis. MB "Tauschaggregat" 617 motor + 4-speed conversion
Alaska Roadtrip 2009
-2002 E320 Wagon - 197k mi
-1998 E320 Wagon - 310k mi - retired