Having owned a few 140's now, one common problem is always setting up the rear suspension to ride as soft and well as we know W140's actually can...
This is a non trivial issue as in many ways when you consider the W140 ride, when correct, is better than anything else out there, as it was designed to literally insulate the passenger compartment from road imperfections. By comparison, many modern cars want you to feel the road. (?) On a Ferrari this is fine, but in a true Mercedes S class car do you really want to "feel" the concrete road. The W140 personifies (or should personify) wafting above it all...
So perhaps we can create a W140 suspension thread and have all of you experts contribute your expertise to help us solve this issue once and for all.
Thanks to MAVA and others we have the transmissions pretty much down...
Everyone initially says accumulators, but while that is necessary, in my experience it never completely fixes it on W140's over 100,000 miles, and often on cras with less miles than that. As you will see from the links below it is much more complex than that, especially on ADS systems.
The M120's have the ADS system. Which years have ADS I and which years have ADS II?
So I am endeavouring to put some links here and share a few experiences:-
1. - If you don't change the accumulators quick enough that can trash your shocks (expensive consequential failure)
2. - If the car is old, you may need to check / replace the sub frame bushings as well as all the normal bushings and suspension parts...
3. - through a forum member I found a W140 specialist in Canada who advised me that the 140 suspension actually has, in his view, many many small adjustments and he walked his talk and as a result my 1999 coupe then suddenly rode sublimely. It was an astonishing difference over how it was before. The dealer had replaced almost all the rear suspension and it still rode crap and this lovely man did nothing but spend a couple of hours tweaking the settings...
We should have him do a fly / road trip down to see us guys...
4. - Here is one of the best quotes I ever found from an ADS expert (see the link below):- "I was not satisfied with the ride quality of my car. It should have been much softer than it was. It always felt too firm. I also could not feel a difference between the Sport and Comfort modes, which pointed to a problem.
To test your car, start it up, and select Sport mode. Push down on each corner as if testing the shocks. There should be give, but it should feel pretty stiff. With the car still running, select the Comfort mode. Again, push down on each corner of the car. You should feel much more bounce now. If you don't, you have a problem."..."My saga to understand this system began last year. There is surprisingly very little information on the web about the details of this system, and a wealth of downright inaccurate info out there as well.
This page [see links below] attempts to describe the ADS system, how I diagnosed my vehicle's system, and what I ended up doing."
Also I have now been to many independents and several dealers and so far no one can fix it the way he did... most in fact tell me there is nothing wrong, especially at the dealers - which is absolute nonsense. I have driven the 140 set up right and it is astonishingly good. Although to be fair most of their more recent techs know very little about the details of 140's. And of course few 140's come in to them.
So I hope the following helps us all:-
I personally now suspect the pump not being perfect or the 1 (or is it 3?) valves on the rear ADS suspension not being right can be factor. And I repeat with every W140 I have had replacing the accumulators, while necessary, is nowhere near enough to get that amazing ride they had when they first came out of the showroom.
I think these are some of the key links - but they no seems to longer work? - Arrgh!
Does anyone have the print off of these they can share? WOULD BE GOLD!!
Ah ha - I found one link to some of it that works - EUREKA!!!
V12 Uber Alles, Repairing a Broken Self-leveling Valve Linkage in a W140 Mercedes Benz
Whoppee - YAY - there's more:-
V12 Uber Alles, Repair Help for Mercedes Benz S600 V12 W140
V12 Uber Alles, Diagnosing the Adaptive Damping System (ADS) in a Mercedes Benz S600
V12 Uber Alles, Changing the Rear Struts in a W140 Mercedes Benz
V12 Uber Alles, Replacing Accumulators (aka Spring Actuators, Nitrogen Spheres) in a W140 Mercedes Benz
V12 Uber Alles, Articles and Info Page
How good are those finds ^ - WOW!!!
Have also found this :-
ADS Tech Main
So here are, as an example, 11 pages of our Benz World brothers trying to understand the ADS, but without the benefit of all of the above links:-
and also, here:-
And more folks worried about harsh ride:-
And please enjoy what these fantastic cars should be able to do:- NO HARSHNESS HERE:-
Anyone who can master these W140 and C140 suspensions is truly valuable to our Mercedes enthusiast community.
I hope the above links are helpful to many, if not all of us.
To smoother motoring, the way the 140s were intended...