560SEC Modified Rear Suspension

Without realizing it, I purchased a 1987 560SEC that has a modified rear suspension.
Evidently the standard hydraulic suspension was replaced with a Mercedes 420 type set-up; just shocks and springs.

I would appreciate any advice, hints, tips on the practicality of converting back to the original hydraulic set-up;

- Has anyone heard of a similar situation?
- Would it be expensive to convert back
to the original hydraulics?
- Would this be a major undertaking?



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'87 560SEC

[Arthur Dalton]

Hate to say it, but forget you looked and save the trouble of having to convert it back to the spring-shock system again later.
They did it for you already.

[stevebfl]

From a technicians point of view, junking top quality systems like load leveling because you can't understand it or afford it is a sorry excuse.

That system is as durable and maintenance free as it gets. The only thing that needs replacement is the accumulators. If you drive a few years with them dead you can beat the seals out of the shocks/struts and possibly the level valve. The same system is on every station wagon.

I would see your local MB junk yard (let me know if you don't have one) and grab all the pieces missing except the acculmulators (those should be bought new as they are perishable - mercedesshop should be able to help there # 123 320 02 15 MB list $130)

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 03-31-2000).]

[TommyMB]

Steve, if one accumulator is low on pressure would it cause the car to sag on one side? Thanks.

Tommy

[stevebfl]

Seems like I just explained this system but it might have been on iATN.

The short answer is NO. The accumulators play no part in lifting the car.

The car is lifted by the strut portion of the shock. The car is slightly supported by these devices even unloaded. When a load is applied the valve is moved by the rotation of the stabilizer bar. Pressure is released into the system (both side are connected to this single feed so the pressure is always the same on both struts and both accumulators). Now picture this: the car is being supported substantially by the struts (now loaded). The hydraulic fluid is not compressable and the car hits a bump in the road.

What happens? .... well we haven't talked about accumulators so the system we have described would drive those ridged struts right up through the fenders. Now for the accumulator story.

The accumulator is a ball the size of a grapefruit. It has one hydraulic fitting/entrance. Inside there is a pressure of Nitrogen gas (probably around 500psi out of the box) against a diaphram and the whole cylinder in filled with the gas holding the diaphram against the walls. The car is started and the pump fills the line to the valve. The car is down so the valve releases pressurized fluid into the system. The fluid, not being compressable, instantly raises in pressure to the 500psi pressure of the Nitrogen in the chambers. The valve keeps letting fluid in as the car isn't yet rising and the pressure rises to say 800psi.

The diaphram has been pushed off the walls of the chamber and the chamber now is a quarter full of fluid with the resulting Nitrogen space reduced and the pressure at the matching pressure of 800psi. Some where around this time the car lifts and the valve shuts down (if too much lift is gained or if the load is reduced the valve lets fluid back out to the system resevoir).

So now we have a supported car riding along and we hit a bump, the strut collapses forcing the fluid to go into the accumulator chamber compressing the nitrogen till it hits 2000psi and the ball is nearly full of hydraulic fluid (quite a bump - think what would happen if that nitrogen is gone and the fluid already totally filled the accumulator chamber - solid as a rock) with the pressure this high the strut rebounds.

If the concept I described sounds something like a spring it is all the accumulators fault as the car is really riding on small high pressure balloons so to speak.

Since pressure is what lifts the car a dead accumulator just fills and when the pressure is right the car lifts. Since both sides are pressurized from one inlet all components receive equal pressure. If one side is lower it is because the steel spring is weak. You must remember the total lift is the pressure imparted by the struts (which is equal - baring some strut problem) plus the force of the steel springs. Alignment geometry can also alter the affect of either the steel springs or the strut force (but the strut force will be equal side to side as a principle of hydraulics - all force within a chamber with be equal).

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks to stevebfl for your reply to my posting but I am a bit confused.

I did not junk the load leveling system as you imply; It was that way when I purhased the car. I'm merely trying to find a means of correcting the situation.
Thanx.

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'87 560SEC

[stevebfl]

Edward,

My reply was directed at the concept and the first reply that you received.

I must say that the format here leaves something to be desired. My reply should have followed some sort of thread line to indicate at which point I replied. It does appear right below the other post so I have a little trouble understanding your confusion.

Since I have no idea of the complexity of making modifications to this format, I haven't complained. It is sometimes hard in long threads to determine who is talking to whom (almost like a chat room). Since I am pointing this out I would also mention that when I do reply (unless I pick the reply w/quote method) I have to remember the whole thread which sometimes has multiple issues. I have learned to use the reply w/quote and then delete the quote, once I have made a full reply.

I have done extensive posting on the iATN and I'm spoiled. Another feature they use in the reply mechanism is to let you see the finished product as it will be viewed and you can go back with your browser to repeatedly edit untill its right. Then you can send it.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[TommyMB]

[QUOTE]Originally posted by TommyMB:
[B]Steve, if one accumulator is low on pressure would it cause the car to sag on one side? Thanks.

Steve, the reason that I asked the above question is because I have an 84' Euro 500SEL with full hydropuematic suspension, no springs. The left front is an inch lower than the right front. I have replaced all the accumulators, shocks, leveller valves, and the front sway bar and it still lean. I am stumped. By the way there is no suspension damage and all the preloads were checked to be correct. Any suggestions is appreciated.

Tommy

[stevebfl]

Tommy,

Thats a different story. The accumulators still work the same way. The struts now are taking all the load. There are 5 accumulators on that system.

You mention replacing a lot of parts but you don't mention adjusting the height valve, which would be the first thing to do. The front struts are supplied by separate valves and are adjusted separately. The rear has only one valve like the load leveling suspension. The adjustments are turn buckle links that attach the valves to the suspension.

Tell me if I misunderstood the question.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[TommyMB]

Steve

The front has only one height leveling controller, just like the rear. It is attached to the front sway bar with elbow linkages. I have just replaced the front level controller at the same time with the sway bar change. I am not aware of individual height valves, where are they located? Thanks

Tommy

[Bill Wood]

quote:

---

Originally posted by stevebfl:
I have to remember the whole thread which sometimes has multiple issues. I have learned to use the reply w/quote and then delete the quote, once I have made a full reply.

Another feature they use in the reply mechanism is to let you see the finished product as it will be viewed and you can go back with your browser to repeatedly edit untill its right.

---

Steve-
There are MUCH EASIER ways to do what you want...

You do not have to remember the entire thread when you reply to a post. Just scroll down with your browser. The entire thread appears in a scrollable window below the window you post your reply in.

You can edit your post as many times as you like by clicking on the edit button.
Your message will be re-posted with the changes you have made.


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Bill Wood - Webmaster
MercedesShop.com, LLC

[stevebfl]

[QUOTE]Originally posted by TommyMB:
[B]Steve

The front has only one height leveling controller, just like the rear.

Sorry about the mis-information. I waited to reply after looking at the hydraulic drawing this mourning. Sur enough the front is like the rear. I must have been thinking of the way the air suspension cars worked.

In this case you will haver equal pressure on each leg. I would look for suspention wear and/or geometry problems.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician