Super-stiff airmatic damping - Help please!

[markbenj]

Greetings all

Greetings all, can anyone help please? (sorry for this long thread)

The Airmatic damping on my immaculate treasured W220 'S' is (always has been) super-stiff at all 4 corners (front to rear, side to side and diagonally). The car runs on standard 17" alloys with OE 225/55 x 17 Continental tyres at the correct pressures with no mods to the suspension, but even low speed minor road ruts and ridges send severe jolts through the cabin as if the entire system is permanently locked into 'safe' (stiff) mode and not releasing / adjusting pressure to the struts according to the conditions. My best analogy is that the car rides (or rather bounces!) over even minor road imperfections like a skateboard.

History: well maintained 2004 car with 120k miles, mine since 2016. Airmatic compressor and relay replaced at 60k miles, 2 x recent 'STAR' diagnostics not showing any fault codes, suspension doesn't lose height when parked up (so leaks not suspected), maintains correct ride height always. Dashboard switch raises / lowers height correctly, but Sport 1 & 2 settings are inoperative although the lights come on. No wiring faults found on recent physical examination, no Airmatic warnings on dash, so I'm completely baffled.

My Question(s): could the problem be due to a faulty / seized valve block (but which for some reason is NOT showing any codes?). Or, similarly, the pressure relief (release) valve in the compressor? So far, 2 Merc Indies haven't solved the problem. All they say is: "the struts actuate ok and we can't see any fault codes on STAR". Mmmm...

Also.. just after buying the car there was a temporary burning rubber smell in the cabin - as if some wires had shorted. Again, is it possible that an electrical / wiring fault might NOT show up on STAR - or at least when the vehicle is stationary?

On another forum there was some mention that the ADS solenoids attached to the struts at all 4 corners aren't getting the correct voltage - and so the ADS system ECU is defaulting to the hardest (of 4 - hard compression and hard rebound) settings in 'safety' mode. Had these tested yesterday with a (non-STAR) OBD scanner when the car was stationary (as opposed to on the move), but it showed that all 4 were drawing current - and no fault codes / dashboard warnings thrown up. So the plot thickens...

All thoughts, advice and experiences welcomed to restore the 'magic carpet' ride that the S Class is famous for - many thanks!

MB

 

[whitenemesis]

Any problems with the steering angle sensor or ASC can put the suspension into stiff mode. In fact any sub system that monitors the cars handling can cause this.
There must be fault codes stored though, suggest you try a different indie.

 

[markbenj]

Any problems with the steering angle sensor or ASC can put the suspension into stiff mode. In fact any sub system that monitors the cars handling can cause this.
There must be fault codes stored though, suggest you try a different indie.

Thanks whitenemesis - will do. Am I right in thinking that a STAR dx is only as good as the operator..?

 

[grober]

Airmatic - W220 S-Class Encyclopedia

 

[markbenj]

Airmatic - W220 S-Class Encyclopedia

Thanks Graeme - yes I have it ;-)

 

[Petrol Pete]

Have you tried Ben at Parkway Automobile Engineering in Fishponds Bristol ? 0117 965 6164

 

[Petrol Pete]

Airmatic - W220 S-Class Encyclopedia

I clicked on this and my security blocked it instantly ??

 

[zipdip]

Well the test I would ask the indie to do is using the Star set the suspension to the soft setting,say 1,as already mentioned I suspect your car is on 4 the hardest setting and when the indie tries to get the car onto 1 it will throw a fault up.

 

[markbenj]

Have you tried Ben at Parkway Automobile Engineering in Fishponds Bristol ? 0117 965 6164

Thanks Pete, I'll give him a ring. Do you know if he has STAR? (apologies - I see he is a Merc specialist)

 

[Petrol Pete]

Thanks Pete, I'll give him a ring. Do you know if he has STAR?

Been around a long time his dad started the business years ago in Parkway (hence the name) , he has pretty much everything. All I know is whenever I have been in there he ONLY has Mercedes Benz cars and it's a 'no frills' operation working in an old building in a tough location. But he has done some big jobs for me at the right price without problems. He is always very busy though, give him a bell.

 

[markbenj]

Been around a long time his dad started the business years ago in Parkway (hence the name) , he has pretty much everything. All I know is whenever I have been in there he ONLY has Mercedes Benz cars and it's a 'no frills' operation working in an old building in a tough location. But he has done some big jobs for me at the right price without problems. He is always very busy though, give him a bell.

Thanks again, just looked at his website. Always helpful to have recommendations from happy customers. Will update when I've spoken with him.

 

[grober]

I clicked on this and my security blocked it instantly ??

Yep its a funny one that. Some folks browsers throw up a warning flag -- others bring up the website with no apparent ill effects. Fortunately that hasn't happened for the OP as its an excellent resource.

 

[markbenj]

Yep its a funny one that. Some folks browsers throw up a warning flag -- others bring up the website with no apparent ill effects. Fortunately that hasn't happened for the OP as its an excellent resource.

Ohhh... the wonders (and mysteries) of technology?! :-D

 

[markbenj]

Well the test I would ask the indie to do is using the Star set the suspension to the soft setting,say 1,as already mentioned I suspect your car is on 4 the hardest setting and when the indie tries to get the car onto 1 it will throw a fault up.

Thanks zipdip, I'm sure you're right about the '4' / hardest setting. The ride is atrocious around town and doing the other suspension components (bushes etc) no good at all. Thanks for the tip - will ask the Indie to do this when he scans it. Thanks again, MB

 

[AMGeed]

Another recommended indy in your area is Steve@Avantgarde in Clevedon
About Us | Avantgarde Automotive, Bristol

 

[grober]

From the section on ADS II in the link above
Limp-home Function
A malfunction in the adaptive damping system causes the ADS to shut down. The suspension is switched to the hardest setting. In the event of a fault in the suspension system or in the level adjustment system, the vehicle attempts to maintain the set level. Manual and automatic level adjustments are no longer possible.
Again fault codes should be registered if its electronic???

 

[markbenj]

Another recommended indy in your area is Steve@Avantgarde in Clevedon
About Us | Avantgarde Automotive, Bristol

Thanks AMGeed. Now you mention it, I did in fact go to Avantgarde with the same issue shortly after I bought the car 3 years ago. Verdict then: 'all ok, no faults stored on STAR'. Similarly with Startech in Poole some time later when an accelerometer went kaput and the car both rode rock hard AND raised to maximum height. Startech's technician also drove the car after fixing the accelerometer and his verdict was (q) 'it rides ok'. Mmm...

The above made me question my sanity but I've driven a mate's 'S' and the difference is night and day....

Maybe time to re-visit Avantgarde as I'm in the WSM area. Thanks again, to be continued..

 

[markbenj]

From the section on ADS II in the link above
Limp-home Function
A malfunction in the adaptive damping system causes the ADS to shut down. The suspension is switched to the hardest setting. In the event of a fault in the suspension system or in the level adjustment system, the vehicle attempts to maintain the set level. Manual and automatic level adjustments are no longer possible.

Yep, got it thanks gaeme. The 64,000 dollar question is 'what is the fault - and whereabouts in the supporting system?' The puzzling thing is that 2 x STAR diagnostics (actually, 3 now I think about it - including an Indie in WSM) haven't got to the bottom of things. Oh well...! If the car wasn't so pristine in other respects I would have got shot of it by now.

Just another thought - is it possible for the fault to be intermittent: i.e. only showing up when on the move? If so, might a STAR test when driving reveal more about what's going on?

Thanks all for your helpful input. On, and forwards.. ;-)

 

[zipdip]

Well the Star diagnostics can do all sorts of things,for instance if your airmatic pump was a suspect the star can empty the air from the tank and then get the pump to fill it again,I think it gets about 5 secs to do it,and repeats the test recording how long the pump takes and if it fails,it follows that there must be all sorts of tests that can be done with your hard ride,I must admit that it surprises me that three indies all recommended in your area should think that a ride in a W220 S mercedes which is making your fillings loose,is ok.

 

[markbenj]

Well the Star diagnostics can do all sorts of things,for instance if your airmatic pump was a suspect the star can empty the air from the tank and then get the pump to fill it again,I think it gets about 5 secs to do it,and repeats the test recording how long the pump takes and if it fails,it follows that there must be all sorts of tests that can be done with your hard ride,I must admit that it surprises me that three indies all recommended in your area should think that a ride in a W220 S mercedes which is making your fillings loose,is ok.

I kid you not zipdip. Yes, all 3 couldn't find any (stored?) fault codes on STAR. 2 techies drove it briefly(admittedly on fairly smooth roads) and felt that the ride quality was / is ok, struts actuate properly, system holds pressure, etc. But it is the LWB version, and so compared with many cars is still pretty good - on smooth roads that is. Maybe they haven't experienced how exceptionally comfortable the ride is on a healthy 'S' suspension set up, on all types of road - my w210 E55 amg estate had a far superior ride! Then again, maybe I'm giving them the benefit of the doubt.

Maybe I need to encourage whoever looks at it next to dig deep into STAR and eliminate all possible causes - or look for multiple causes? No disrespect to the 3 Indies but it does make me wonder if they just check the essentials (e.g. safety) and don't have the expertise, patience, interest and / or training to use STAR to its full capability. Who can know?

The only good news is my fillings are surprisingly intact despite this - probably bcs I now know every rut and ridge in my local WSM roads more intimately than the local highways department, and weave around them like on an obstacle course. In an S Class? Ohhhh.... !

BTW - how is your S Class ride quality, have you had any problems with it? Pity we're not closer or it would be good to drive both and compare notes.

Again, thanks zipdip and all - to be continued...