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1995 E320 Wagon, 2002 S430
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594 Posts
Discussion Starter #1 (Edited)
Hello, have a bit of a head scratcher here for you all. My 95 E320 Wagon is having some issues withe SLS system it appears. When I get in the car in the back (with car on or key turned), I hear NOTHING going on back there and the car does not move up or adjust to the weight. Also, on the drivers side, the suspension back there is very tight/bouncy/rough, whilst the drivers side is very soft and sloppy almost. I have seen posts all over the forum on the SLS and replacing the spheres/accumulators and such, but nothing ever about the motor or fuses. I wanted to ask first of all, is there a fuse associated with the SLS motor or height detection sensor. Second, shouldn't I hear the motor working at least, even if the spheres/accumulators are shot and don't hold anything? Shouldn't I hear it attempting/failing to adjust? Last week I DID hear a motor turn on back there for about ten seconds when my daughters got in but now absolutely NOTHING. Any ideas anyone? Thanks.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,668 Posts
Pressure for the system comes from your power steering pump. TE SLS systems all work in this manner and the steering pumps are different than those on sedans/coupes/cabs. There will never be any action unless the car is running. Soft, bouncy or hard suspensions symptoms are more often cured by replacing the accumulators (spheres). You'll find more than you can read on this subject by using the search function of the site.

My 2.3 16V 190E also has the SLS system but it's powered by a separate pump driven off the nose of the exhaust side cam. The rear suspension was rock hard when I purchased the car. New accumulators solved the problem.

Good Luck,

Jayare
 

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Banned
1993 400E
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7,361 Posts
Pressure for the system comes from your power steering pump.

Good Luck,

Jayare
Yes that's correct, though it's really 2 pumps in one.

The pump is called a tandem pump. The p/s half and SLS half use seperate fluids.

They get turned on a common shaft but are sealed from each other.

Older SLS systems like Jayare's have a seperate pump on the engine. A W126 500SEL uses such a pump as does M617 deisel W123's.
 

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95 E300, 91 300TE, 84 190D
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777 Posts
As to your questions, there is no SLS fuse, there is no SLS motor back there, and it does not make noise when the height is adjusted. The ten second noise you heard "back there" was likely the antenna motor.
 

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Registered
1995 E320 Wagon, 2002 S430
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594 Posts
Discussion Starter #5
As to your questions, there is no SLS fuse, there is no SLS motor back there, and it does not make noise when the height is adjusted. The ten second noise you heard "back there" was likely the antenna motor.
Thanks for taking the time to respond to my head scratcher. The antenna motor is disconnected, we heard something...motor like. I have read on the forums that when the SLS is activated (putting lots of weight in the back), you can hear it/feel it adjusting. So...is that incorrect? What pump in the car fills the spheres or accumulators? As I understand it, they are filled with air? If the accumulators are filled with air, what part of the SLS system uses the hydraulic fluid dedicated specifically for that purpose? I have not seen a post that puts it all together, there are bits and pieces scattered here an there (helpful and informative, but scattered). Also, when we go over a speeed bump (and this is likely not related to the SLS) the left rear suspension makes a distinct "gapunk" sound almost like the sound of gas being compressed and then leaking in a burst from the strut. Is that just the sound of compromised strut?
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,668 Posts
Here is the long and short of it. The "sound" you hear when you initially go to start the car is in all likelihood the fuel pumps pressuring up the system. They shut off when things are "pumped" and begin working again after the engine is running.

As stated by ClarkZ71 and me earlier, the SLS system is driven from the tandem pump (power steering pump) only when the engine is running. The accumulators contain two chambers. One is filled with high pressure gas and the other with hydraulic fluid. There is a rubber diaphragm that separates the two. The purpose of the gas side is to absorb the "shock" when bumps are hit. The "gapunk" sound may be a bad bushing on one or more elements of the rear suspension.

Hope this "gathers" things up for you and good luck,

Jayare
 

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1996 Mercedes-Benz S500
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721 Posts
i would have to disagree with you i know the noise he is talking about! i have an s500 with sls. and when i was adjusting the rear end, (lifing it) it made a whinding noise as the car was rising. and cuts off when it gets up there.... its not an antenna or fuel pump.... i do believe the fuel pump should have already built pressure before you started the car... and personally ive never heard it with the car on!
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,246 Posts
i would have to disagree with you i know the noise he is talking about! i have an s500 with sls. and when i was adjusting the rear end, (lifing it) it made a whinding noise as the car was rising. and cuts off when it gets up there.... its not an antenna or fuel pump.... i do believe the fuel pump should have already built pressure before you started the car... and personally ive never heard it with the car on!
There's no way, unless your car's SLS system has residual, trapped pressure when the key is turned off and it's attempting to level the back. It's a pump driven affair that has to have the motor running for the system to operate correctly.

Kevin
Approve REF.71
 

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1987 300TD - 1981 300D - 1990 190E 2.6 (Non Running for Sale) - 1993 190E 2.3
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285 Posts
Testing

If you want to test it, do as follows:

Get underneath car, either by crawling if there is enough room, or by backing onto ramps. Get a 10mm wrench and disconnect the tie rod looking arm from the SLS Valve lever. Move the linkage arm out of the way and adjust the valve left UP. Up makes it go up. However it will not raise up until you drive off of ramps. Once I drove it off, I reached under and moved the valve, waited, then did it again until I liked where it was.

I was thinking I had some critical issue with mine until I did this. Let us know what you find.
 

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1990 300 TE 190,000 - Sold - Should have kept it.
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104 Posts
For what it's worth:

I recently had the accumulators replaced on my 300te. They went bad one side at a time, giving me similar results as you've experienced.
By the time second one had failed, the ride was so bad that one small speed bump broke both rear exhaust hangers.

With new accumulators installed by an authorized MB mechanic, the ride height does not raise or lower at all when I start or turn off the car. The only time any change is noticed is when I "load" the rear of the car. At that time the SLS will adjust itself, without making any noise.

When I turn the ignition to the first position without starting the car, my fuel pump does make a sound for a few seconds and then stops.

Hope that helps a little.
 
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