S211 E220 Estate Suspension issue Ongoing

[atlantimd]

My S211 has an on going issue with rear self-levelling suspension. The car lowers during the night on one side only. There is a history with this car since 2021 left side lowers overnight

Both rear airbags were replaced and due to the left side still dropping after replacement I had both airbags replaced under warranty and I have the same issue with the new airbags. The replacement airbags are Aersus from Germany
Once the car starts in the morning the compressor lifts it by the 2” approx. I have noticed lately that the car is not level when parked with RH rear higher by about a half inch.
I carried out a lot of trouble shooting in 2021 and can confirm
I have checked airlines with soap water ok
Checked the one rear height sensor is intact not broken
Checked air compressor under left wheel arch ok
There are no extra air tanks on this model just the airbags on rear and coil spring on the front self levelling on the rear.

I have witnessed the car drop after being let down of a jack which is normal to level the car and you can hear the valve energise and de energise to release the air pressure
I believe that even if there were leaks in the airlines this would not be the problem, as the air should be held in the airbags overnight. For some reason the car is energising the air valve in the top of the airbag right side and releasing the pressure as there are no leaks.
I have icarsoft but not STAR can anyone confirm is there a menu in star where you can reset the rear heights although looking online the STAR menu looks like there is nothing to do this.
With the recent cold weather the car is lower in the morning I suppose that is to do with air density in cold nights
Any help would be great as I like the car but it will wreck the pump and does not look good in the morning sitting one side down with the wheel in the wheel arch.

 

[atlantimd]

Any suggestions to this issue?

 

[Willber]

Im no expert and it sounds like you have explored the obvious potential causes. Getting it on Star would help? Also, could it be something to do with the valve block (is there one?!) where the air lines go into? Sorry, I dont know much about air suspension but if its not the bags or compressor then it must be something else letting air out, or distributing it to the wrong place?

 

[atlantimd]

Im no expert and it sounds like you have explored the obvious potential causes. Getting it on Star would help? Also, could it be something to do with the valve block (is there one?!) where the air lines go into? Sorry, I dont know much about air suspension but if its not the bags or compressor then it must be something else letting air out, or distributing it to the wrong place?

Thanks for the reply. There is no valve block as its self levelling. I think compressor, controller, 2 airbags and level sensor. and No leaks.

 

[Willber]

The air must be going somewhere though? Either to the other airbag, or leaking. I dont see how it can sink otherwise?

 

[atlantimd]

The air must be going somewhere though? Either to the other airbag, or leaking. I dont see how it can sink otherwise?

Yes I agree with you. I think the car is releasing the electric air solenoid on top of the airbag and releasing air

 

[MCFastybloke]

Air is leaking or something is telling it to lower, are you able to look at the sensor live data?

 

[atlantimd]

Air is leaking or something is telling it to lower, are you able to look at the sensor live data?

I am not sure how yet. I have icarsoftMB but I think I may need to somehow look at CAN data

 

[GreenLaner]

I used my icarsoft MB II device to view sensor data on my 2012 model. Given the various heat shields and things I couldn't get a clear view of all the pipes, so just put in a replacement (very cheap to buy anyway) and it resolved a similar issue.