W220 Airmatic continuing HD (‘Hard Damping’) problem / Help please?!

[markben]

Greetings all on this friendly & helpful forum.

As briefly as I can describe: my otherwise immaculate & well-maintained 2004 140k mile S320L cdi has always suffered from an overly Harsh / Stiff ride in Comfort mode during my 7-year ownership, and far from the legendary ‘Magic Carpet’ ride quality despite 4 x new OE Mercedes supplied air struts + numerous other investigations.

I’ve been let-down & disappointed numerous times by my local + a few other Mercedes Indies who usually say any or all of ‘No faults on SDS and / or it rides ok!’ despite my knowing better. I know how smoothly & softly Mercedes S-Class cars should ride (even pre-airmatic W126s & W140s) from my past days as a Mercedes Sales Exec & latterly a Mercedes Head Office Senior Sales Trainer in the early 2020s.

So, my Question: can anyone here recommend a reputable & reliable Mercedes Indie anywhere in the UK (ideally in the south-west) who:

• Has Specialist (I Stress Specialist!) knowledge of, and is experienced in diagnosing & fixing more complex Airmatic issues.
• Is willing to initially review a detailed / written summary of previous work & investigations done on my car + the symptoms if it helps them to propose a more thorough diagnostic process & possible solution(s).
• Then, and in conjunction with / subject to their response as above: to test-drive my car on ‘bumpy / lumpy’ roads so as to (hopefully) agree with my description of the ‘Hard Damping’ symptoms - or advise me otherwise.

For me: it's ‘Money-no-Object’ to fix my HD problem and about finding a conscientious & suitably experienced Mercedes Indie who is both interested-in and has the time, patience & technical ‘know-how’ to fix it.

I am willing to travel to, and leave my car for a few days with a suitably interested Indie who is willing to take-on this challenge when many others have shied-away from and / or (of more concern) ‘Gaslighted’ me into believing that my Airmatic Hard Damping problem is (quote one politely .. ‘imagined’). Enuff said?

Many thanks in anticipation

Mark B.

 

[rf065]

A few years ago someone recommended Land Rover dealers/indie's as having more experience on air suspension than Mercedes only garages. Might be worth speaking to some of them?

 

[malcolm E53 AMG]

Have you considered having the suspension arms re-bushed or replaced? I remember having a Dolomite Sprint in the day and re-bushing the front suspension arms the car drove totally different like a new car

 

[robmc52]

OP, I can't find the other thread you had running about this, but I do remember posting a couple of times on it as my W220 exhibited the same symptoms as your car, but I seem to have accidentally discovered what the problem was, with my car at least.
The car needed some welding done on the inner wings, the black plastic boxes that house the SAM units and various ecu's had to be removed so that my man could access the ****** great holes that were hidden underneath them.
I disconnected everything from the looms on the passenger side, unbolted the box, then reconnected everything and wrapped them in plastic bags to keep moisture out until I took it to the garage the day after. My man was going to do one side at a time so I started with the worst affected area.
The moment I set off the next day it was obvious that something miraculous had happened to the suspension. The ride was, and still is, absolutely superb, gliding over bumps and potholes like they weren't there. I couldn't believe it at first, but even the wife commented how comfy it was.
So the sum total of improvement seems to be unplugging the suspension ecu and plugging it in again, maybe it just needed the contact pins cleaning, or I did think disconnecting the battery for a couple of hours while I twiddled around under the bonnet might have reset the ecu? I really don't know.

 

[Blobcat]

OP, I can't find the other thread you had running about this, but I do remember posting a couple of times on it as my W220 exhibited the same symptoms as your car, but I seem to have accidentally discovered what the problem was, with my car at least.
The car needed some welding done on the inner wings, the black plastic boxes that house the SAM units and various ecu's had to be removed so that my man could access the ****** great holes that were hidden underneath them.
I disconnected everything from the looms on the passenger side, unbolted the box, then reconnected everything and wrapped them in plastic bags to keep moisture out until I took it to the garage the day after. My man was going to do one side at a time so I started with the worst affected area.
The moment I set off the next day it was obvious that something miraculous had happened to the suspension. The ride was, and still is, absolutely superb, gliding over bumps and potholes like they weren't there. I couldn't believe it at first, but even the wife commented how comfy it was.
So the sum total of improvement seems to be unplugging the suspension ecu and plugging it in again, maybe it just needed the contact pins cleaning, or I did think disconnecting the battery for a couple of hours while I twiddled around under the bonnet might have reset the ecu? I really don't know.

Previous thread below:

W220 S Class Hard Damping HELP Please?!

Greetings all Has anyone here had problems with overly-hard damping in their S class? Despite 4 new Mercedes Reman OE air struts & valve block, numerous 'No Fault' SDS reports & many other more obvious causes eliminated, my Adaptive Damping is 'stuck' either in Sport 2 or Level 4 Hardest /...

forums.mercedesclub.org.uk

 

[markben]

OP, I can't find the other thread you had running about this, but I do remember posting a couple of times on it as my W220 exhibited the same symptoms as your car, but I seem to have accidentally discovered what the problem was, with my car at least.
The car needed some welding done on the inner wings, the black plastic boxes that house the SAM units and various ecu's had to be removed so that my man could access the ****** great holes that were hidden underneath them.
I disconnected everything from the looms on the passenger side, unbolted the box, then reconnected everything and wrapped them in plastic bags to keep moisture out until I took it to the garage the day after. My man was going to do one side at a time so I started with the worst affected area.
The moment I set off the next day it was obvious that something miraculous had happened to the suspension. The ride was, and still is, absolutely superb, gliding over bumps and potholes like they weren't there. I couldn't believe it at first, but even the wife commented how comfy it was.
So the sum total of improvement seems to be unplugging the suspension ecu and plugging it in again, maybe it just needed the contact pins cleaning, or I did think disconnecting the battery for a couple of hours while I twiddled around under the bonnet might have reset the ecu? I really don't know.

Many thanks rob. My W220 is a late 2004 facelift model & well cared-for, so no corrosion anywhere - hopefully!

That said: I'm sure you're onto something about possibly 'dodgy \ weak ' connections in the airmatic / ADS electrical wiring loom (contact pins etc) due to any or all of age, corrosion, shorted wires etc - which, from what I can gather, can cause the ADS ECU 'Brain' to close-down the ADS at the (4) individual strut electronic damping valves and default to 'Level 4 / Hard Compression & Rebound / Driving Safety' mode.
Your wife's observations are really helpful: 'absolutely superb.. 'gliding over.. (Magic Carpet ride?)' etc' after you did some tweaks. That's exactly the Night & Day / equally unbelievable difference when my W220 very occasionally & momentarily 'glides' over even minor road bumps & dips - as it should!

I've had my local auto electrician swap the original ECU for used / tested equivalent one - with no difference to my Hard Damping 98% of the time (even in Comfort mode). So I hope that eliminates an ECU 'glitch'. But.. your reply reassures me that, somewhere in the system, the most likely cause is as simple as a 'dodgy / weak' electrical contact - but which has evaded many Indies in their efforts to trace it. (Or.. maybe.. because they just can't be bothered to? Mmmmm...).

Either way: thanks for your encouraging reply. It gives me renewed confidence that my judgement about my HD problem is accurate despite a couple of Indies having suggested (q.) "it rides ok, are you imagining it?!". No further comment about a couple of (un-named) Indies - including my local one in W-s-M.

Thanks again & to be continued..

 

[markben]

Have you considered having the suspension arms re-bushed or replaced? I remember having a Dolomite Sprint in the day and re-bushing the front suspension arms the car drove totally different like a new car

Thanks malcolm, I get your point. I've had my front arms & bushes replaced with OE. But no difference to my HD problem, so I hope I've eliminated that cause at least?

 

[tavernole]

Greetings all on this friendly & helpful forum.

As briefly as I can describe: my otherwise immaculate & well-maintained 2004 140k mile S320L cdi has always suffered from an overly Harsh / Stiff ride in Comfort mode during my 7-year ownership, and far from the legendary ‘Magic Carpet’ ride quality despite 4 x new OE Mercedes supplied air struts + numerous other investigations.

I’ve been let-down & disappointed numerous times by my local + a few other Mercedes Indies who usually say any or all of ‘No faults on SDS and / or it rides ok!’ despite my knowing better. I know how smoothly & softly Mercedes S-Class cars should ride (even pre-airmatic W126s & W140s) from my past days as a Mercedes Sales Exec & latterly a Mercedes Head Office Senior Sales Trainer in the early 2020s.

So, my Question: can anyone here recommend a reputable & reliable Mercedes Indie anywhere in the UK (ideally in the south-west) who:

• Has Specialist (I Stress Specialist!) knowledge of, and is experienced in diagnosing & fixing more complex Airmatic issues.
• Is willing to initially review a detailed / written summary of previous work & investigations done on my car + the symptoms if it helps them to propose a more thorough diagnostic process & possible solution(s).
• Then, and in conjunction with / subject to their response as above: to test-drive my car on ‘bumpy / lumpy’ roads so as to (hopefully) agree with my description of the ‘Hard Damping’ symptoms - or advise me otherwise.

For me: it's ‘Money-no-Object’ to fix my HD problem and about finding a conscientious & suitably experienced Mercedes Indie who is both interested-in and has the time, patience & technical ‘know-how’ to fix it.

I am willing to travel to, and leave my car for a few days with a suitably interested Indie who is willing to take-on this challenge when many others have shied-away from and / or (of more concern) ‘Gaslighted’ me into believing that my Airmatic Hard Damping problem is (quote one politely .. ‘imagined’). Enuff said?

Many thanks in anticipation

Mark B.

Hi markben, there are electrical connections near the top of each suspension points in the engine bay, disconnect them and spray with contact cleaner, that should solve the problem, I had to do the same on my W221, it worked.

 

[markben]

Hi markben, there are electrical connections near the top of each suspension points in the engine bay, disconnect them and spray with contact cleaner, that should solve the problem, I had to do the same on my W221, it worked.

Thanks tavernole, will do. I'll also ask my local auto electrician to do the same with as many other airmatic / ADS electrical connections as he can get at. As mentioned, although my ADS is quite stiff 98% of the time (as if stuck in Sport 2 or Level 4 Diving Safety mode), it occasionally, briefly but dramatically softens up - so it can and does work, if only sometimes!

My best guess about the cause is along the lines you suggest, and I hope it's just case of finding that bad connection. A bit like finding a needle in a haystack? but worth the time & effort to restore the Magic Carpet ride.

Will update here as & when I've made progress.

 

[robmc52]

Hi markben, there are electrical connections near the top of each suspension points in the engine bay, disconnect them and spray with contact cleaner, that should solve the problem, I had to do the same on my W221, it worked.

Are these the acceleration sensors? When I first bought my car, six years ago now, the ride suddenly went very hard. My indy did the same as you and the fault went away. He said low voltage from them will make the car revert to the safe driving mode, as Markben mentions.
I'm sure my icarsoft will measure the voltage of these sensors in real time, I might try it later if it stops raining....

 

[tavernole]

Are these the acceleration sensors? When I first bought my car, six years ago now, the ride suddenly went very hard. My indy did the same as you and the fault went away. He said low voltage from them will make the car revert to the safe driving mode, as Markben mentions.
I'm sure my icarsoft will measure the voltage of these sensors in real time, I might try it later if it stops raining....

No, these are not sensors, they are plug connections very near the top of the suspension units in the engine bay on both sides, they don't sit on top of the suspension, but close by, they might be the signal connections to the suspension units

 

[robmc52]

No, these are not sensors, they are plug connections very near the top of the suspension units in the engine bay on both sides, they don't sit on top of the suspension, but close by, they might be the signal connections to the suspension units

The connector blocks that go through the strut tower?

 

[tavernole]

The connector blocks that go through the strut tower?

I will have a look at mine tomorrow, I will try and take a photo of it