Greetings All. Thanks if you’ve made helpful comments on my previous posts, but the stiff ride problem continues despite eliminating a few things. Here’s a reminder / update:

The car & history: 2004 S320L cdi SE version. 128k gentle miles, well maintained, mine for past 3 years. Runs on OE 17” alloys with new Continental OE 225/55/17 97Y rated tyres (not XL) at correct pressures, no mods. Recent new front suspension arms, track control arms, wheel bearings, tracking perfect & drives straight. New Compressor & relay at 70k miles. New OE Valve Block just fitted (tested voltage from compressor / solenoids working), new engine & transmission mounts. Strut ADS module connectors checked for seating, appear ok.

Persisting Symptoms (despite the above): very stiff / almost non-existent (!) damping at ALL 4 struts (as if defaulting to setting ‘4’ Safety Mode / hard compression & rebound?) even at very low speeds over ruts and ridges (Thump / Bounce, Ouch!). New Valve Block has made ZERO difference to the stiff, skateboard-like ride. ‘Sport’ 1 & 2 setting switches illuminate, but little difference (unsurprisingly?). I did notice a brief burning smell from the front of the car early in my ownership (hidden shorted wiring as someone suggested?), but nothing obvious when inspected.

(Before you ask): Never any ‘sagging’ even when car not used for a few days. No hint of air leaks, struts actuate ok, ride height even & correct, raises and lowers on dash switch. 3 x previous SDS (‘STAR’) diagnostics NO faults shown or stored even when tested on the move. No ‘Airmatic Warning’ signs on instrument cluster. (Before you ask): no, the harsh ride is not q. ‘maybe in my imagination?’ (as one Indie politely suggested - Mmmmm.. no comment). And yes: I’ve driven a ‘healthy’ (suspension-wise) W220 S Class. The difference is night and day - even allowing for the UK’s often poor road surfaces.

I see that a few W220 S Class owners with a similar problem have replaced air struts at huge expense but with no improvement: so I don’t want to go down this route on the off-chance. And, since the problem is affecting all 4 struts (+ no leaks), it seems unlikely that they have all gone bad.

My Question(s): 1. what might cause the apparent default to setting ‘4’ on my Airmatic / ADS but NOT show any fault codes on STAR? (Mechanical, electrical, or a combination?) 2. Has anyone had a similar experience / symptoms and managed to resolve their stiff damping the problem?

Any suggestions to diagnose the problem / restore the Magic Carpet ride which the S Class is famous for? I’m posting this on a couple of Mercedes forums but this seems to be the best - so will try to keep track of and respond to all replies. Many thanks for your interest in the meantime.

Mark B.

 

The Airmatic system has two subsystems - the air system and the strut dampening system. Your problem is almost certainly due to the dampening subsystem, and almost certainly has nothing to do with the air subsystem.

Go here https://w220.ee/Airmatic and go to section 6.14 and study it carefully.

Do you have any problems at all with the brake lights?

 

I too, after spending the last 15 months working on my car, on and off that is, am experiencing the same issue! I have replaced the front struts with RMT rebuilt ones as well as have rebuilt by RMT Rear Air Springs and brand new OEM Rear Airmatic Shocks on each side, so I was thinking I would have ensured myself of a good “feeling” ride after so much effort. Don’t get me wrong, the 3.06 Rear Gears install along with LSD (from 2.82) pair harmoniously with the M156 Engine and the 722.9 Tranny, but the ride is very stiff.

When I pull out Xentry and go to Suspension testing every sensor comes up but when I test for Acceleration Sensor (ie-Dampening) Power, interestingly it tells me “it is not ok” however when I check for voltage within the same subset (3 sets of checks per sensor) it shows voltage and asks for me to confirm, which I do (Yes). In the first position of the 3 it requires you to switch off the ignition and to mount/attach your breakout box before switching back on the ignition. I like most of you don’t have such a breakout box that you would have to hook up to the control module somewhere in the passenger footwell. Somehow all 3, FR,FL and Rear dampening (ie-acceleration control’led”?) sensors are all showing the same condition? I’ll add that I checked every sensor and all seem normal. The suspension holds air, even though I’m having trouble calibrating ride hight in that after getting a “successful” initial startup calibration, it wants to revert back to a previous setting. While driving, the height will lower as expected in the front at speed an regain height again getting off the highway, so the level sensors are working. It’s just the dampening sensors seem to be not working. It would be sort of crazy for all 3 to suddenly stop working, so I’m thinking I may have missed something. During removal of the rear subframe, I had to disconnect everything, and while doing so, I even installed a new rear wire harness and surely hooked it up properly, otherwise Xentry wouldn’t be able to communicate and enable me to manually raise and lower on demand. As for each shock harness connection in the rear Wheel Wells, there’s really no way to mess that up as they only fit in one way, even so I color coded each before removal! I do have both of the rear Trunk internal lights disconnected as I have removed the rear carpet and opened up each side in preparation for a stereo install, but I can’t imagine that being tied-in with the Airmatic System? I have a SAAB that would cause crazy faults of such a thing were disconnected as their circuit would flow in the wildest patterns! For example a loose tail-light might render you unable to start the car!

I have heard of the front Acceleration Sensors going out, located right next to the Airmatic Front Strut on each side of the engine bay, but in my case, all 3 are not working, and that seems next to impossible! I’d really appreciate anyone’s feedback along these lines! (As per my realization below, I had “misunderstood” this test as in the first position of the test for these sensors, I “did” see a value which meant it was “OK”. It’s in the second test where it states if there was NO Value, then…)

9/01/21- Ok, I want correct my misunderstanding of the readings I mentioned above. That first position when “testing” the sensors in Xentry/DAS actually is to test for “Actual Value” whereby of it reports there is a. “Value”, then the system is “OK”. The 2nd is to “test” for Power whereby the prerequisite is that in Test#1 there was NO report on actual value and the result was “not OK”. In this test you are then to switch off ignition, then hook up the “Break Box” switch on ignition and measure values from each side of the box whereby both must add up to the range provided in the parameter provided in the “Test”. The 3rd “test” is for “voltage” and since my “Actual Value” was OK, it reports voltage in this view, even though the heading states the prerequisite is that “Actual Value” was “OK” but Power was not “OK”. I ultimately went through every test, but it wasn’t until I pulled up in the WIS Suspension>Airmatic> ADS and or semi-automatic where I found the factoid referencing that the Damping System will go into “ Safety Mode” of the Steering Sensor isn’t initialized, say after the battery power is turned off for a significant amount of time, or, in my case, both that and the fact I disconnected the airbag and steering wheel, in order to get the leather redone on it as well as the shifter, for about a month. So it was essential that I “initialized” the Steering Sensor. Whether it requires you to do it in Xentry/DAS and confirm “yes” or not, I’m not sure. But the initialization requires only that you steer the wheel lock-to-lock. When doing it in Xentry, you’ll see how many degrees you’re turning the wheel and it asks for you to confirm each side measures past 400*. After that, the ADS system worked beautifully, even though when I kept the Xentry/DAS connected during my test ride, it for some reason always has caused for the “lift suspension” light to go on as well as both lights of the ADS, which result in a rough ride as both lights of the ADS indicate both Compression and Rebound are harder, but not as hard when the Steering Sensor was NOT Initialized. During the test ride, I could “automatically” adjust ride hight, but even doing so, while it would set the ride hight to what I programmed it to, all lights of the “ADS and Lift” remained on. I could see while driving that the level sensors were constantly changing and would regain composure at the stop light. On highway, it would clearly show up to minus 20mm for the front at speed yet level off as it should when exiting the freeway. However, it wasn’t until I disconnected Xentry from the OBD Port that I regained function of the ADS and all was good again!

 

Since this is a W220 Forum, I'm not sure how many people will know anything about your car - I know that I can't help you at all. Good luck!

 

I did have my front left strut disconnected for over a week whilst I replaced all control arms ball joints and steering rack. Replaced the strutt, everything back together new tyres, was a dream. Took to a merc specialist (not stealers) for a wheel alignment, great alignment and back to absolute rock hard suspension again. So no idea. The suspension was stiff as prior to doing the front end work.
To be honest when I accelerate quite quickly on the hwy to get up to speed it's bloody scary, as when I go over a bump I feel like I'm going to loose control of the car. Inputs or resolution to this would be appreciated.
Thanks

 

First suggestion is to double- and triple-check the two cable connections between the front suspension and the fender liner on both sides. It is really difficult to get those plugged in correctly. It will be easier if you remove the single fastener that holds the level sensor to the upper suspension arm to get better access.

 

Yea the connections not completely and firmly plugged in is the reason usually

 

If you removed the steering column (or the airbag/wheel), you will need to hook up to the OBD Port the Star/Xentry/DAS and not only pull up Airmatic and manually check all the sensors and make sure they are working by activating them. If not, then you you can go to a different menu to go through guided tests to determine if you have power etc., as I explain in my previous post above. Of all is ok there, good. Then you have to make sure the Steering Sensor is “initialized”. As I mentioned before, I am not certain if you absolutely need Star/DAS when doing this as it simply requests you to turn the wheel lock- to-lock and then confirm Y or N. In my case, when I did this using DAS, my ADS returned to normal function again. I may mention that before I realized this, I was able to adjust Ride Height manually and it would automatically lower at speed and I was able to select the different “features” of ADS by selecting “off”,1 light , or 2, but before I used Xentry again as described, although I could select functions, it would remain rock hard (ie- it was in Safety Mode)…

 

hi there
I have the same issue with my w220, for more than a year, with no solution yet. But i do have BRAKE LIGHT ISSUE on das that keep coming in fault codes - i will post picture of that.
any solution with that?
thanks
Y

 

I didn't read the whole thing, but I want to throw out there: Ride Height Calibration. Costs ~$400 and is done in conjunction with an alignment.

 

Hi Mark. Since I can’t msg you directly due to your settings just wanted to ask you re your battery drain issue. Think it was you. Could be wrong. Getting old 🤔🤨😜 Turned out to be in you trunk lock?! If so Plse send me a direct message about it.

 

Have the same problem that the ride is very harsh and wanted to know if you managed to fix the issue?