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1999 Mercedes Benz S320 Long Wheelbase.
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544 Posts
Discussion Starter #1
I'm pretty sure my auto leveling rear suspension isn't working. When I load up the car with four of my friends, the rear end sags bigtime, at least it did right after I loaded them up in it...I didn't check later. Maybe it takes time to adjust?

But if I park on an incline, it's almost like the car is trying to level the rear end out by bringing it up a bit. And it's very rare that I hear the compressor anymore when I start it up....either I can't hear it because it's not as cold as it was earlier, or it's just not working.

Anyways, I heard that the accumulators are the common problem on these. Is that true? Does that sound like the culprit? What do they usually cost to have done at a dealer or indie shop?

Oh, and I apologize if this topic has been beat to all hell.
 

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1989 560sl, 2016 G63
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168 Posts
Those pesky accumulators

I am having mine done as we speak at the stealership. Will let you know the cost when they let me know.

The gas within these accumulators has a shelf life of roughly 8-10 years. This according to my service advisor. Of course low milage may allow for an extra year of so but the nitrogen (?) leaks out and causes a rough ride from the arse and unstable reaction over from the car over bumps. I watched the ride quality of my W140 go from brilliant to absolute crap in a span of about two months.

Hope this does the trick. I hope to get a price on te job today from W.I. Simonson....subtract 50% for specialist price, but I can't find a decent one in these parts.

Cheers,

R.
 

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SEC 600 V12 2dr COUPE (RHD) One of the chosen few.
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2,233 Posts
If your acumalators are shot you wont get any lift.. so test it yourself.... start the engine.. go sit on the trunk lip with your feet just touching the ground.. then see if it lifts.. shouldent take more than 90 seconds to lift you back level.. look in the knowlege base for more info...
 

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Looking for V8 W140
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96 Posts
The maximum trunk load is 100 kg (220 lbs). Four friends might be too much. Besides, I was told it would take about 90 sec to bring the rear up.
 

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1993 300SEL (Sold) 2007 X5
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The maximum trunk load is 100 kg (220 lbs). Four friends might be too much. Besides, I was told it would take about 90 sec to bring the rear up.
That can't be right, on my filler cap it tells me the tyre pressues for 4-5 people and luggage which must be more that 100kg's.
 

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1998 S500
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446 Posts
If your acumalators are shot you wont get any lift.. so test it yourself.... start the engine.. go sit on the trunk lip with your feet just touching the ground.. then see if it lifts.. shouldent take more than 90 seconds to lift you back level.. look in the knowlege base for more info...
Why is this true? As long as the level is off, the leveling valve should be activated which should supply pressurized fluid to the rear struts to change the level. This seems like it should still work even if the accumulators are bad.
 

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1999 Mercedes Benz S320 Long Wheelbase.
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544 Posts
Discussion Starter #9
There was a time a few months back when I drove four friends down to a casino. We stopped about 1/2 way and I got out and saw that the back end was sagging a lot too. And the car had been running for 30 minutes before I got out and checked.

What else is there to go bad? The pump?
 

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That can't be right, on my filler cap it tells me the tyre pressues for 4-5 people and luggage which must be more that 100kg's.
Oh, I am sorry. I have missread the original post. The rear definitely should not sag with four-five people inside and empty trunk.
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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The self leveling pump is tandem to the power steering pump. It is a loop system the flid goes to the valve attached to the rear axle and is routed to the strut/accumulator or back to the reservoir. The accumulators are spheres with a diaphram inside, on one side is nitrogen the other side is fluid and is connected to the strut by a hose. The oil gas combination act as the dampening agent to thr strut (shock look alike). You can cgeck it by moving the lever the car should rise and fall.
 

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1999 Mercedes Benz S320 Long Wheelbase.
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544 Posts
Discussion Starter #12
Where is this lever?

Alright, so after I got home last night, I parked the car, opened the trunk and sat on the sill, with my feet on the ground for atleast 60 seconds, and I could not feel the rear end raise or decline at all. Do I have to try it when I first turn the car on after it sits all night?
 

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1997 S600 (sold)
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4,660 Posts
Where is this lever?

Alright, so after I got home last night, I parked the car, opened the trunk and sat on the sill, with my feet on the ground for atleast 60 seconds, and I could not feel the rear end raise or decline at all. Do I have to try it when I first turn the car on after it sits all night?
Here are some pictures: V12 Uber Alles, Repairing a Broken Self-leveling Valve Linkage in a W140 Mercedes Benz

I replaced a broken linkage arm between the anti-roll bar and the levelling valve. To orient you a bit, the pictures were taken from the left side wheel well with the wheel removed. The valve and linkage are really tucked up tight under the body of the car and as you can see in the pictures above the left side axle half shaft.

To operate the levelling valve manually, you will have to release the linkage from the valve. This may not be easy due to corrosion. Easiest thing to do is to put the rear wheels on ramps if you want to manually test it.

The suspension is always active. You don't have to wait for it to self-level, but you do have to put enough weight on it to drop the car enough to move the valve arm enough to open the valve and allow fluid to flow to the struts.

Brett
 

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96' S500, 09' S550, 06' SL65
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208 Posts
Brett,

Always nice to hear a voice of reason.

I assume in this application, the air charge (nitrogen) on one side acts as the opposing force within the accumulator to the (hydro side). I also assume the accumulators are more for pressure balancing and absorbtion rather than pressure storage as they are used in many jet aircraft. When the nitrogen goes away all your are left with is a dome full of fluid and since fluid is non compressible, you get a very hard ride.

Kudos to those that have sucessfully converted the P/S pump and struts to conventional, but I am also proud to have renewed my ride with new accumulators and hydraulic struts (I had the infamous strut knock). I was lucky and found a couple of new struts for about the cost of one discounted strut.

There is something very satisfying about turning the key to wake that long S500 in the morning and watching it immediately rise up in the haunch about a half inch or so....the beast is alive!

Even if we all have staked out our positions on the self leveling suspension at least we know it can't be as cantankerous as the discussions on the Citreon SM forum.

I'm on the level..........................................
 

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1999 Mercedes Benz S320 Long Wheelbase.
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544 Posts
Discussion Starter #18
Yes, it is optional on the 320 and 420, standard elsewhere. I believe my car has the option, but I'm not 100% positive. I've seen what looks to be hydraulic lines running longitudinal near the rear axle, on the underside of the car, but I'm not 100% certain they're for the suspension. I was told the fluid reservoir or pump mechanism is under the hood, under a cover on the driver's side...is this correct?

Last winter, when it was very cold out, I could hear a pump running from what seemed to be the rear end when first started in the mornings....it sounded like the pump for the air suspension on my Cadillac did. But now that it's warmer out, I don't hear that sound anymore.
 

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1997 S600 (sold)
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4,660 Posts
but I'm not 100% certain they're for the suspension. I was told the fluid reservoir or pump mechanism is under the hood, under a cover on the driver's side...is this correct?
I would suggest you confirm whether you have the self-leveling suspension before wasting any more of your and our time.

Yes, fluid reservoir location is correct. Pictures are on the forum in other posts.

Brett
 

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1999 Mercedes Benz S320 Long Wheelbase.
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Discussion Starter #20
I would suggest you confirm whether you have the self-leveling suspension before wasting any more of your and our time.

Sheesh....sorry. I thought I'd try it out on here first before I called down to Feldmann and spoke to their advisors too see what they thought. Well it turns out by giving them the VIN number that I do have the self leveling suspension, and it seems as though it is faulty because it doesn't seem to level it's self out with a heavy load in the rear end. He said off the top of his head, accumulators are about $900 to replace and the pump is about $1300.
 
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