Another SLS question

[500ESpain]

Let's imagine I'm not talking here about my 81 300TD (especially you W123 haters) but as the systems are very similar, if we were, the conclusions could apply for W123, W126 and W124 models.

The thing is that I recently bought a 300TD that I'm restoring. It was a mess, especially suspension wise. In the back they added big metal pads on top of the springs to rise the suspension. Not very good for the SLS sytem I think. The rear suspension was hard and felt that the car was just leaning on the springs.

I took the whole rear axle down and replaced every piece of rubber on it. Regarding the SLS system I replaced the spheres (they were obviously gone, the suspension was harsh), fluid flush, filter, strut bushings and the ball joints on the bottom of them (replaceable on the W123, as you know).

After that I was expecting to have a perfect rear end but no. The harshness is still there. When going over potholes or coming down the curb of the driveway it's hard and it clunks. When driving at speed the car feels bouncy, like if it was just leaning on the springs as before.

There's a noise you can here from the trunk right on top of the SLS valve. My mechanic says it's definitely a valve sound. So there's obvioulsy something wrong there.

Apart from that, the manual says that with the back loaded and the engine running the fluid level on the reservoir should drop but it doesn't.

It looks like the fluid is not running properly through the system but I can't tell if the problem is the SLS valve not working or the pump not sending enough pressure to the system. I guess the valve is noisy because it doen's have enough fluid inside.

My understanding of the system is very basic so you might have better theories about what is going on.

Thanks in advance!

 

[gerryvz]

Definitely sounds like either the valve, or the accumulators. Since those are new, I'd check the valve. All motion/springiness in the system is controlled by the accumulators. The SLS hydro-legs are only there for leveling purposes, and (essentially) serve as reservoirs of hydraulic fluid. The SLS hydro-legs are only connected to the accumulators; the accumulators (and high and low pressure lines to the hydraulic fluid reservoir and radial piston pump on the 123, both up front in the engine compartment) are attached directly to the leveling valve.

Thus, the level control valve is the choke point in the system. I'd source a new (I mean, used -- these valves are HELLA expensive) leveling valve, and ensure that your accumulators are not damaged in any way. If the system is not damping correctly, then there is likely not fluid in the accumulators that is pressing against the rubber membrane that has a charge of nitrogen on the other side. The leveling valve controls the flow of hydraulic fluid to the accumulators.

My best guess, is that perhaps one or more of the lines is not connected to the correct port on the hydraulic valve. Meaning a line to an accumulator is connected to a pump- or reservoir-line valve. Can you double-check that the right lines are connected to the right ports on the valve?

These SLS valves do not fail very often. They take a LOT of abuse. You should be able to source a spare from an early 126, or another 123, etc.

Good luck !!

Cheers,
Gerry

 

[500ESpain]

Thanks, Gerry

I'll try to find reference pictures to see if everything is attached where it should. The only fluid lines I touched were the ones going to the accumulators. Maybe someone before messed with the valve lines but as they are metal and shaped I think it's difficult not connecting them properly but anything could have happened after seeing how the car was messed with.

Since you said the leveling valve controls the flow of hydraulic fluid to the accumulators and there's a noise coming from the valve I think the problem is there.

I've been looking for the valve and they're not very common here in Europe. I just found one and pricey. If you know about agood source forthis in the States, pleaselet me know.

Thanks again!

 

[gerryvz]

I see them at the wrecking yards. I try to keep a couple of spares on hand for my cars. Did you try US eBay perhaps for one?

 

[500ESpain]

Yep, just two available. One "will probably need to be rebuilt" and one with cracked port. In Europe I just found one in Germany but for 350 euro. Half of new dealer price but still expensive. I will probably get that one if I can't find anything else.

If any of you find one in the scrapyard I'd really appreciate it.

Thanks!

 

[gerryvz]

Crap, I just pick them off of cars for free here in the US for my cars. Any 560SEL and many other models have these things.

Perhaps someone here on the forum has a spare. Captruff? David Hendy? Jono? Stevester?

 

[gsxr]

Hmmm. Guess I need to pay attention to the occasional 126 that I see in the junkyard!

 

[gerryvz]

Yes, indeed. The 126 (560SEL/SEC) SLS valve is the same valve that is used on the E500E, and many other models. Thus, it is a good idea to have a spare or two on hand.

I know, I know Dave ..... heresy to have a 126 part on an E500E. But it happens !!

This SLS valve is also used in a wide variety of other MB applications, not only on the 126 (560SEL/SEC), but also on the 124, 210, 208, 140, 202, 129, and 203 chassis.

The current SLS valve part has been superseded several times. If you buy one now, it's a 202 part number. Specifically, 202 320 02 58. Current MBNA MBUSA list price: $505.

Previous versions of this part number include 123 320 02 58; 124 320 00 58; and 202 320 00 58.

 

[500ESpain]

I had 123 320 0258 and 1153280521 for the W123 chassis. You mean those other p/n would fit too?

 

[gerryvz]

I had 123 320 0258 and 1153280521 for the W123 chassis. You mean those other p/n would fit too?

Sorry -- I was getting off on a tangent there banging on with GSXR, and forgot you were talking about the 123 chassis. It's not often we discuss those on this forum.....

That is a very different design of a valve than the 126 and onward chassis I mentioned. I do see them from time to time on 123 models here in the yards, though not with the frequency that I see the 126+ valves. I see fewer 123 wagons in the yards than I do the sedans (240Ds and 300Ds). Damn ADD....

The correct 123 TD wagon valve would indeed be a different number - 123 320 01 58. That particular valve is only used on certain EARLY W126 models, as well as lots of 123s, and a smattering of 114/115 and (so optioned) 116 models.

 

[500ESpain]

No worries, I wanted to keep a low profile on my W123 ownership. It's not always all about Fire&Silk. There's some Shake, Rattle & Roll in my life too.