A New Rear Suspension Scenario

[groovinola]

Today was the big day! New (used) struts installed, new accumulators (out of the box) installed, new stabilizer link put in, bubble flare put on end of pressure line and reconnected to pressure hose, compression fitting joining return line back together with supply tank. Fluid filled. Rear end up on ramps (supported) and raised 12.75" from star on hubcap to top of wheel well (This info came to me by chance this weekend after looking 3 weeks for it everywhere). 330 lbs placed in passenger compartment of car (guessed at this number but confirmed by Giles in one of my other threads related to this "operation" Strut Installation on '82 TD Wagon: Help). I tighten down the upper suspension of the struts. Tight, ready for the big test.

I say a prayer to the DIY God's and start the car. First thing I look for is leaks. Nothing pouring out, not a drop to be seen anywhere. whew, big relief. I remeasure; distance down to 11+". I get under the car, disconnect the stabilizer link, and start moving the control arm on the Suspension valve. seems like the valve isn't working but then after moving it around a bit the rear end begins to rise and fall. I finally manipulate everything into place and tighten with the rear end at 12.75" on each side (actually the passenger side seems to sit a 1/2'' higher but I'm ok with this).

I drive off the ramps feeling good about my efforts and abilities to fix a problem I never thought I could have done myself just six months ago and then it happens. The drivers side bottoms out on the ramp as i'm driving off, I get out, look at the back and see that the car is all the way down on the drivers side rear (10.5") and almost all the way up on the right side (@16").

Needless to say this looks quite funny but aside from that I am totally perplexed by what caused this to happen. I got the car back up on jacks and disconnected the stabilizer link again and started playing with the valve arm again and the skies opened up and i had to give it up for today.

What are your thoughts on this? I think either the valve is bad (I have a back up out of my parts car I am going to try) or the perhaps the Strut on that side is bad but I don't see any leaking coming from it and it doesn't explain why the passenger side raised when the drivers side collapsed. As always any and all input is appreciated.

peace,
woody

[dennislarock]

PLEASE CREDIT to Biodiesel300TD... THIS IS HIS POST


W123 Self-Leveling-System


The Self-Leveling-System (SLS) adjusts the height of the rear end when it is loaded to keep the rear end at the proper riding level. The springs maintain the unloaded height. The SLS maintains height when loaded.

The distance from the highest lip of the arch of the wheel well to the center of the Mercedes emblem on the wheel should be 12.75” (inches) unloaded. 12.75” should be the maximum height that the SLS will raise the rear end under load.

1) The rear springs support the vehicle when unladen
2) The SLS is only utilized when weight is added to the wagon.
3) Raising the rear of the vehicle with the control linkage will shorten the life of the accumulators.
4) If the rear is low, coil springs and or bump pads (coil spring shims) are needed.
5) When the control rod is properly adjusted a pin can be
inserted thru the actuator arm into the control valve.

Failure – Symptom

Pump failure - Rear doesn't rise when loaded.
Suspension Valve failure - The rear settling or sagging after sitting for many hours, and the rear doesn't rise when loaded.
Accumulator failure - Rides bouncy and/or hard, rear bounces like when you have bad shocks.
Strut failure - Rides bouncy, but not hard.
Sway bar link failure - Clunking when going over bumps.
Coil Springs & Bushings - Clunking when going over bumps


Diagnosing a failed part

Many of the problems that arise in the SLS are caused by or cause leaks, so the main thing is to look for leaks. Wipe down all the SLS parts and then drive for a while. Then crawl back underneath and poke around to see if anything is leaking. If you see leaks you'll know what is leaking.

Pump - Measure the distance from the center of the Mercedes emblem on the wheel to the highest lip of the body of the wheel well, measure both sides, and write down the numbers. Then load the rear with about 300 pounds (2 adult people), measure the distance like before. Then start the car and see if the rear lifts up. Then measure the distance again. It should be really close the first numbers. If the rear doesn't lift at all the pump is likely failing.

Suspension Valve - This valve is located just in front of the rear axle/differential, slightly on the drivers’ side. If it is leaking there is a rebuild kit for it. It's called a Washer Kit, and I believe it's only available at the Dealership.

Accumulators - Diagnosing this isn't as easy, the accumulators have a rubber bladder in them, with suspension fluid on one side and air on the other. They can get holes in the rubber and then the fluid gets into both sides and the accumulator is shot.

Struts - From what I have read struts aren't usually the source of problems with the SLS, the rarely go bad. But when they do the usually start to leak, so they will have suspension fluid on them and they shouldn't.

Sway Bar Links - These are "S" shaped plastic parts with two pivotal bolts on each end. There are rubber booties that cover the connection of the bolts and the plastic. If the booties are gone or torn then are probably shot. Even if the booties are in good shape the link may still need to be replaced. Pull it off and try to pivot the bolts. If the bolts flop around or are easy to move you need new ones. They should be stiff.

Coil Springs & Bushings - Measure the distance from the center of the Mercedes emblem on the wheel to the highest lip of the body of the wheel well measure both sides, and write down the numbers. The height should be 12.75” unloaded. If the height is less than 12.75” then the coil springs have probably compressed over time and you need to install Coil Spring Shims.

Coil Spring Shims come in varying thicknesses of 9.5mm, 14mm and 19mm.

Additionally, this would be a good time to replace your rear suspension bushings… especially if you hear clunks going over small bumps or while just driving on a rough road at very slow speeds. Replacing the bushings, shims and sway bar links will quiet your car and reduce a tremendous amount of stress on the rest of the SLS system. With a set of bushing tools from Harbor Freight $29.99 and about $60.00 in bushings, shims and sway bar links you can go a long way to improving and maintaining your entire SLS system.

Remember ** A word about proper ride height: The unloaded curb weight of the car should be carried entirely by the springs (i.e. If the car has good springs, the unloaded car won't sag even if the SLS is disconnected).

Biodiesel300TD

[peterhardie]

I'd say a bad accumulator before a bad shock. Never seen a bad new one, but.... You could swap the accumulators, they are identical IIRC, to see if you have a bad one.

The shock should leak.

The other possibility is a bad valve. I rebuilt mine with a kit (about $75, look around, probably MB), not real hard to do, it is spring loaded, so you have to go REAL slow and REMEMBER EXACTLY how the metal cam came out. Everything else is fairly clear, some seals and springs and ball bearings, and if in doubt I found a pic of the valve opened up that saved my a$$ when I wasn't paying close attention.

You could save time and $$$ if you find a used one in a recycle yard and swap it in. That would likely expose the valve as the culprit or not.

[Biodiesel300TD]

dennislarock, next time you copy and paste a DIY write-up I did would you please let it be known where it came from. Here is the original. - http://www.schumanautomotive.com/forums/showthread.php?t=2226
I think it's great that you are passing on info, thats what these forum are all about, but please give credit where due.

[Biodiesel300TD]

If one side is sagging, I would suspect the components on that side first. The accumulators probably aren't bad since they are brand new. I would suspect the strut. If they are reverable you might try switching the two and see if the sagging move to the other side. If the valve were the problem it would have been sagging on that same side before you did everything, unless some gunk got into the line for that side.

My thoughts on rear sagging is the springs hold the car at proper ride height, but when they get tired the let the rear of the car drop down thereby telling the SLS that the rear is too low so it lifts it up. So now the SLS is maintaining the ride height more than the springs are. This puts undo stress on the SLS, which causes problems and leaks.

[JimmyL]

Originally Posted by Biodiesel300TD

If one side is sagging, I would suspect the components on that side first. The accumulators probably aren't bad since they are brand new. I would suspect the strut. If they are reverable you might try switching the two and see if the sagging move to the other side. If the valve were the problem it would have been sagging on that same side before you did everything, unless some gunk got into the line for that side.

This sounds like a prudent course of action.

Originally Posted by Biodiesel300TD

My thoughts on rear sagging is the springs hold the car at proper ride height, but when they get tired the let the rear of the car drop down thereby telling the SLS that the rear is too low so it lifts it up. So now the SLS is maintaining the ride height more than the springs are. This puts undo stress on the SLS, which causes problems and leaks.

Please don't take offense at my question, but where did you get your information about the coil springs providing the correct ride height? When a wagon sags overnight, it is universally understood that the suspension valve needs rebuilding. However, it the coils springs hold the height, it shouldn't sag.
There is also a factory adjustment for the ride height. Why would we need an adjustment if the "static" parts {coil springs} set the proper height? {unless that adjustment is only when it is loaded I guess} Also, it would seem like the dampening dynamic would be thrown off if the springs hold the car going level, and only a downward force effected the SLS.
So, I guess I'm asking you to give credit to your source.....

[kerry]

Originally Posted by JimmyL

Please don't take offense at my question, but where did you get your information about the coil springs providing the correct ride height? When a wagon sags overnight, it is universally understood that the suspension valve needs rebuilding. However, it the coils springs hold the height, it shouldn't sag.
There is also a factory adjustment for the ride height. Why would we need an adjustment if the "static" parts {coil springs} set the proper height? {unless that adjustment is only when it is loaded I guess} Also, it would seem like the dampening dynamic would be thrown off if the springs hold the car going level, and only a downward force effected the SLS.
So, I guess I'm asking you to give credit to your source.....

We've had this debate on other SLS threads in the past. There are certainly people here who think the springs should hold it level. I am not yet convinced and I think that even in the 'normal' position, the SLS is carrying some (small?) portion of the load.

[JimmyL]

Originally Posted by kerry

We've had this debate on other SLS threads in the past. There are certainly people here who think the springs should hold it level. I am not yet convinced and I think that even in the 'normal' position, the SLS is carrying some (small?) portion of the load.

I'm with you, and that is why I asked for the source.
{apparently sources are very important...}

[groovinola]

Looks like my new "partner in crime," Dennis, brought this thread back to life. Just to update on the situation. Two things were going on simultaneously that had exacerbated the situation. The first was that the springs were not properly seated, especially on the passenger side. That one wasn't sitting in the groove and both had a peice of rubber around the end on the base (which apparently they do on 126 springs?). The second, and by far the main contributor to the whole situation was that when i drove the car down off the ramps the drivers side front tire went into a hole and the passenger side front was sitting up high on a tree root. This threw everything out of whack. As soon as the springs were replaced and the car was sitting on level ground all was good.

I ended up driving the car up to Massachussetts for the summer and just got back to NOLA two weeks ago- (about 5k miles for the summer). The suspension worked great but when I brought the car in to get new tires (4 Sumitomos at Sears for $100-story for another day) and it was up on the lift I noticed the passenger side strut was leaking so i will need to be replacing that soon. During the summer I needed to replace the passenger side axle shaft and my radiator. Luckily I found a guy (who sells parts on e-bay) who got me a brand new behr for $240 which i was able to go and pick up from him directly in Williamsburg, MA. He has a ton of parts up there. I also got some great assistance from a mechanic in Shelborne, MA named John Allen.

[Biodiesel300TD]

The coil spring info didn't come from me. Here is what I wrote.
http://www.schumanautomotive.com/forums/showthread.php?t=2226

[warmblood58]

Originally Posted by dennislarock

PLEASE CREDIT to Biodiesel300TD... THIS IS HIS POST


W123 Self-Leveling-System


The Self-Leveling-System (SLS) adjusts the height of the rear end when it is loaded to keep the rear end at the proper riding level. The springs maintain the unloaded height. The SLS maintains height when loaded.

The distance from the highest lip of the arch of the wheel well to the center of the Mercedes emblem on the wheel should be 12.75” (inches) unloaded. 12.75” should be the maximum height that the SLS will raise the rear end under load.

1) The rear springs support the vehicle when unladen
2) The SLS is only utilized when weight is added to the wagon.
3) Raising the rear of the vehicle with the control linkage will shorten the life of the accumulators.
4) If the rear is low, coil springs and or bump pads (coil spring shims) are needed.
5) When the control rod is properly adjusted a pin can be
inserted thru the actuator arm into the control valve.

Failure – Symptom

Pump failure - Rear doesn't rise when loaded.
Suspension Valve failure - The rear settling or sagging after sitting for many hours, and the rear doesn't rise when loaded.
Accumulator failure - Rides bouncy and/or hard, rear bounces like when you have bad shocks.
Strut failure - Rides bouncy, but not hard.
Sway bar link failure - Clunking when going over bumps.
Coil Springs & Bushings - Clunking when going over bumps


Diagnosing a failed part

Many of the problems that arise in the SLS are caused by or cause leaks, so the main thing is to look for leaks. Wipe down all the SLS parts and then drive for a while. Then crawl back underneath and poke around to see if anything is leaking. If you see leaks you'll know what is leaking.

Pump - Measure the distance from the center of the Mercedes emblem on the wheel to the highest lip of the body of the wheel well, measure both sides, and write down the numbers. Then load the rear with about 300 pounds (2 adult people), measure the distance like before. Then start the car and see if the rear lifts up. Then measure the distance again. It should be really close the first numbers. If the rear doesn't lift at all the pump is likely failing.

Suspension Valve - This valve is located just in front of the rear axle/differential, slightly on the drivers’ side. If it is leaking there is a rebuild kit for it. It's called a Washer Kit, and I believe it's only available at the Dealership.

Accumulators - Diagnosing this isn't as easy, the accumulators have a rubber bladder in them, with suspension fluid on one side and air on the other. They can get holes in the rubber and then the fluid gets into both sides and the accumulator is shot.

Struts - From what I have read struts aren't usually the source of problems with the SLS, the rarely go bad. But when they do the usually start to leak, so they will have suspension fluid on them and they shouldn't.

Sway Bar Links - These are "S" shaped plastic parts with two pivotal bolts on each end. There are rubber booties that cover the connection of the bolts and the plastic. If the booties are gone or torn then are probably shot. Even if the booties are in good shape the link may still need to be replaced. Pull it off and try to pivot the bolts. If the bolts flop around or are easy to move you need new ones. They should be stiff.

Coil Springs & Bushings - Measure the distance from the center of the Mercedes emblem on the wheel to the highest lip of the body of the wheel well measure both sides, and write down the numbers. The height should be 12.75” unloaded. If the height is less than 12.75” then the coil springs have probably compressed over time and you need to install Coil Spring Shims.

Coil Spring Shims come in varying thicknesses of 9.5mm, 14mm and 19mm.

Additionally, this would be a good time to replace your rear suspension bushings… especially if you hear clunks going over small bumps or while just driving on a rough road at very slow speeds. Replacing the bushings, shims and sway bar links will quiet your car and reduce a tremendous amount of stress on the rest of the SLS system. With a set of bushing tools from Harbor Freight $29.99 and about $60.00 in bushings, shims and sway bar links you can go a long way to improving and maintaining your entire SLS system.

Remember ** A word about proper ride height: The unloaded curb weight of the car should be carried entirely by the springs (i.e. If the car has good springs, the unloaded car won't sag even if the SLS is disconnected).

Biodiesel300TD

Can you identify "highest lip" of the wheel arch" by this do you mean the lower edge of wheel arch place where tire could make contact if wheel was extended out (in roughly the center) or the flared area that forms the wheel arch about 3 inches about lower edge (the eyebrow) I want to get the measurement right -thanks!