Is it possible to re-pressurise S211 air suspension without Star?

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MJJ

Active Member
Joined
Jan 13, 2020
Messages
135
Location
Wiltshire
Car
'09 S211 E220 CDi manual - 197k miles and counting
Hi all,

I have recently fitted some new Bilstein rear air suspension bags to my S211, as the NS was starting to drop occasionally when left for many days. Fitting of the new bags went smoothly, though I cannot get the compressor to start running to pressurise the system prior to lowering it onto its wheels. The car (on axle stands) of course thinks it is too high as the suspension is fully extended, so I assume the compressor only kicks in when the car is low - I don't want to lower the car until there is at least some pressure in the bags.

All the online advice (and Bilstein's instructions) suggests I need Star to do this. I have iCarSoft CR Pro but that can just read some suspension data, it cannot command anything.

Anyone got any experience of getting round this? I am tempted to unplug the compressor from the loom, and simply feed it 12V from another battery.

Thanks for any advice anyone can offer,

Martin.
 
Hi,

When I replaced the air suspension units on my S212, I put the trolley jack under the jacking point to take the weight of that side, removed the axle stands and lowered the car until that side was at about the correct height (wheel on the ground and at about the correct position in the wheel arch) and then started the car.
The pump started to pump the suspension and it took the weight. I then lowered the jack.

That was a bit easier for me as I only replaced one air suspension unit at a time.
If you have replaced both sides and have the whole of the back of the car in the air on axle stands, you'll need two jacks.
Not as easy or as stable.

How did you get the car up onto the axle stands?
 
Thanks for that @steveq. I could do the same, as I just put a trolley jack under the differential to raise/lower both sides at once.

I am very wary about having to lower the car significantly before the compressor kicks in though. I have read that the S211 system won't trigger the compressor until the car is 20mm lower than expected ride height, and I don't really want to put the bags under that sort of compression before they are inflated.

It sounds like your 212 kicked in earlier than 20mm too low, so perhaps the control strategy changed on the 212.

My current thought is to try and remove the level sensor from the car, and manipulate it manually to fool the car into triggering the compressor.

Martin.
 
I'd try feeding it 12V and see what happens, and if it runs, you know the compressor is serviceable. If it is, clean up all its connections and see if it then works normally. If not, try moving the level sensor manually as you have suggested.
 
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The thread replies this afternoon prompted me to go and try to solve this, so I can now post a solution in case it helps others in future.

So, I can confirm (via CarSoft live data) that the S211 ride height needs to read -20mm (i.e. 20mm lower than normal) before the compressor kicks into action to pressurise the system. Of course you could achieve this by lowering the car gently off the jack until it is at that -20mm ride height, but I did not like the idea of putting stress on empty bags.

So, two easily accessed 10mm bolts removes the ride height sensor from the rear subframe, and it can be manually manipulated to read below -20mm whilst the car is still on axle stands and at full suspension extension. The engine does not need to be on, just ignition in position 2. You can easily hear the compressor spring into life, and I let it run for 10 seconds or so to build pressure. You will get a 'Car too low' dash error message at this point because the car does not see plausible suspension data.

Then, refitted the level sensor, and lowered the car gently to the ground. The car started to raise itself at that magic -20mm point again.

Hope this helps someone in the future.

Martin.
 

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