Suspension Dropping W212

[billy21]

My 2010 E-Class estate (W212 or S212) has air suspension at the rear and I've noticed that it drops right down over the wheels intermittently - especially when cold. It's been like that for about a year and nothing came up on STAR when I had it checked. It always drops evenly on both sides and returns to normal height when the ignition is started. Has anyone experienced this before? and if so is there a way of righting it? I'm assuming the physical components are fine and it's more likely to be a sensor or software fault?

 

[Mattns]

My 2010 E-Class estate (W212 or S212) has air suspension at the rear and I've noticed that it drops right down over the wheels intermittently - especially when cold. It's been like that for about a year and nothing came up on STAR when I had it checked. It always drops evenly on both sides and returns to normal height when the ignition is started. Has anyone experienced this before? and if so is there a way of righting it? I'm assuming the physical components are fine and it's more likely to be a sensor or software fault?

I assume the car drops over time when ignition is off if that's the case I would suggest the most probable cause is air leaking back through the control block valves and not software, usual cause for valve block leaks is dirt or rust like tarnish allowing slow leakage?

 

[CowleyStJames]

Mine does this when cold, also when parked up you can hear a slight hiss when you turn engine off.
This is a normal procedure to remove some pressure from the airbags so they're not in a high pressure state when car is left.
Well that's what my MB dealer told me when I asked them to diagnose that problem with mine.

 

[steveq]

My 2010 E-Class estate (W212 or S212) has air suspension at the rear and I've noticed that it drops right down over the wheels intermittently - especially when cold.

Your car shouldn't drop down overnight. There is a problem with the air suspension units, the air lines, the valve block or the level sensors.
The pump is having to work hard to inflate the air suspension when you next start the car. That pump will eventually burn out.

The air lines are cheap to replace if they are leaking but it might be difficult to find the leak.
I suggest that you go around the airlines with soapy water to find the leak.
The valve block on the S212 is underneath the car behind the rear bumper. That could be leaking too.

I also suggest that you also measure the rate of dropping by measuring the height of each side when you stop the car and then again the following day before you start.

Are you parking on level ground? The self levelling will try to keep the rear level so could let air out of one side to compensate for a slope.

This is a normal procedure to remove some pressure from the airbags so they're not in a high pressure state when car is left.
Well that's what my MB dealer told me when I asked them to diagnose that problem with mine.

That sounds a bit dubious. It is like letting the air out of the tyres to remove the high pressure and give them a rest!!!

I have an S212 which was dropping overnight and had to replace the air suspension units. Each side was dropping at a different rate though -- one side was overnight but the other took 2 - 3 days of non-use before it was fully down.
Since replacing the units the car does not drop at all -- even after leaving it in an airport carpark for 2 weeks.

 

[billy21]

Thanks everyone - the cars in the garage today so hopefully I'll find out more soon.

 

[Will]

How did you get on with this?

I’d go along with steveq, my 2011 S212 had a very slight leak when parked up - only noticeable at first after several days but once I spotted it you could notice it begin to drop a few mm each day over the course of a week if not used daily. Which was the difference between being able to put your hand between the top of the tyre and the wheel arch, and over a week the tyre would be half covered by the wheel arch.

No codes on STAR, or warning lights on the dash. No issues when driving either - just annoying as I knew it shouldn’t do it. You probably wouldn’t know if you weren’t looking for it, or were using the car on a daily basis.

Took it to a local MB specialist - no leaks found on any of the air lines/compressor/valve block, but they measured the drop whilst parked and it wasn’t my imagination. Warranty paid for new air springs (aka bellows/airbags) from MB plus fitting and it has been sat 5+ days since I picked it up and it has not dropped at all since

It was dropping pretty much evenly both sides, which is perhaps the only thing that was a little unusual as you may not expect them to leak/fail as evenly as that, but they did.

Anyway - just thought it may be of use to the OP, it was the air springs on mine