S212 rear Airmatic drops after drive

[BillyBob]

’13 E 350 CDI estate. 100k miles.
Only at the rear Airmatic struts, as standard.

I’m having weird issues with Airmatic suspension.

During this winter (0 celsius to -3 celsius) rear has fallen 3-4 cm both sides during night.

I have Star and Xentry doesn’t find any fault codes and Xentry passes all the tests for compression and valve tests. No any messages in odometer for ”Please wait” or ”Stop! Vehicle too low!”

Firstly I opened compressor and dried silical gel granules in the oven. There was little a bit moisture in drier unit but that was sorted out by drying silical gel granules and cleaning the whole unit. This didn’t help.

Secondly, indie MB workshop changed all the airlines and checked air struts condition and found no issues. But they couldn’t tell by outside since there is protective boot outside.
So they attached their own made valve to both sides of air struts. Then they applied compressed air from outside of the car to fill up air struts. Valves both sides were closed so they could detect if there was leak in the other sides. Car was driven to outside cold weather and measurements were taken for over night (16 hours). Vehicle was dropped both sides only 1cm, but they claim its normal since they fill up with warm air inside the garage and temperature change is reason for that volume change.

Unfortunately that didn’t help.

After these jobs done I’ve found something interesting.

1) I drove car in warm garage for over 12h garage and took measurements and no rear drop at all.

2) The rear has dropped for 3cm both sides during over night parking. After that I have started the car without changing position and let the car compressor raise to normal level and shut off the car immediately, the rear keeps it’s level after that rest of the time for next 12 hours.

Somewhat problems seems to be in after driving, warm air in air struts and in outside temperature (especially in zero degree celsius).

Much has been checked and ruled out. I don’t believe air struts are broken if the vehicle keeps it level in warm garage and compressing cold air without changing position.

Do you have any idea where next to go find the cause, or is it just normal by temperature/volume change and is it zero degree climate issue?

Edit: Correction in details

 

[steveq]

I assume that you have the Self Levelling rear suspension that is standard on E Class Estates.
Your car dropping 3cm isn't much and it could be just the warm air cooling and compressing overnight.

I found that my S212 dropped more noticeably in cold weather. One side was worse than the other but both would have dropped more than 3cm overnight.
After 3 - 5 days of non use the rear of the car was completely down with the tyres under the wheel arches.

The most likely cause is the rear air suspension units starting to fail (as you already have had the air lines checked for leaks).

Unfortunately, no faults will be displayed on Star unless to say that the car is too low.

I replaced both rear suspension units and resolved the problem.

 

[Will]

Suspension Dropping W212

For what it’s worth, I left it parked for well over a week (in fact, 12 days total..) and it had not dropped one bit.

So it was definitely the air springs on mine (aka air bags/bellows etc)

When I went to use it yesterday, I could swear the ride is better too. It feels more supple, more compliant, less crashy.

Seems quite a common issue on 212s with air at the rear, but I guess if you’re using the car daily you might not notice straight away.

 

[BillyBob]

Yeah it's the self leveling rear suspension (as standard on estate) and not officially "Airmatic" but somehow it's easier to call the system "Airmatic". Sorry about that.

It's so weird that it doesn't do dropping in every condition, like I told previously that in warm garage there were no issues. For example today I left from work after 12h and rear was in normal level and measurements from center of the wheel cap to the wheel arch proofed it that there was no sinking. Parking space level is quite flat. The car was parked outside as I do in my home parking space so outside conditions were perfectly the same.

In my home parking space there is a little bit of tilt. Somehow rear looks it has some "cargo load" in my home parking space. It's already 1cm down compared to when I park it to flat level. When I wait for 3-4h and rear has dropped again evenly 1cm.
After that system has cooled down and I start engine for 30-60 seconds to raise level up, it gets to same level as at flat level and it holds level normally.
This issue only becomes evident at my home parking space. No where else. In my previous home address there were no issues since parking space level was flat.

I don't know, it's quite frustrating to find out that is there even a problem and what is causing the issues. Indie MB workshop said that air suspension troubleshoot is quite challenging and many fixing attempts go by changing new parts and hoping that new parts resolves issue. It is just so weird that car can hold the air in certain conditions, and by that you could make conclusion that if there is a leak in air struts, it would drop level all the time. But since it is air suspension, you can't always be sure.

I might change next time both air struts. I know they are not really that expensive, but again if I change them and it doesn't fix this issue, which is not yet even proofed that problem even exists, it is just upsetting to pay and hope that would resolve.

 

[whitenemesis]

Air pressure in the system will drop as the ambient temperature drops. So, as it cools down the volume in the air bags will reduce lowering the car.

 

[Will]

Just to clarify a few things:

There’s no air struts, just air springs. You still have a conventional damper.

I wouldn’t get too fixated on the temperature issue. At most, it’s just highlighting an underlying problem. Yes air can expand/contract when hot or cold, but don’t you think MB have thought of that? Do your tyres go flat overnight in the cold?

And even when parked in the heat of the summer the air will still cool overnight thus shrinking in volume. There’s probably more temperature variations (hence volume variations) in the warmer weather anyway.

On that basis - if it drops overnight (when it drops below freezing), does it rise back up again as the air expands when it warms back up again? If not you have a leak.

Like I was saying I left mine parked up for well over a week recently including days with similar temperature variations (ie below freezing overnight) and it hadn’t dropped - so for you to have noticed a drop overnight then you likely have an issue. Prior to this I’d started to notice a slight drop whilst parked up for a day or two and if left for several days it was quite noticeable. Back in the warmer weather I’d not noticed as much, so it’s possibly related to the cooler weather we have now showing up the issue more.

The airbags are probably the most likely culprit being made using rubber, this seems relatively common - I would guess they have a crack or split somewhere that is shrinking and leaking slowly as they cool etc. If your workshop has checked all the other components what else can it be?

Google S212 air suspension for reassurance, it’s more common that you maybe realise.

 

[BillyBob]

Replaced left rear air spring with a new one. Quite easy job. This was the side which notably dropped.

Star compression test showed clearly best compression results for left side. Ride is normal.

But rear left still falls down.

So for the record:

-No fault codes. All test passes normally.
-Compressor granules have been changed.
-Air hoses have been changed
-Rear left air spring has been changed

And still rear left corner is falling down. Not all mornings but fairly 80%. And clearly not all places.

Any idea where the problem lies? Desperation starts to creep in.

 

[Weds]

I have a S212 which had a dropping problem which was slowly getting worse, dropping down a lot in an hour or so (worse in the cold weather) A few months before this I'd already tried soapy water check which showed up nothing.
Thinking most of the problems appear to be the bellows I had these both changed, still it would drop, I'd pop back to the indy that changed them for more checks but still no leaks. So I decided to change the air solenoid as we couldn't find any leaks in the pipework, still it dropped.. As there was only one thing left to change I got them to change the pipework and so far it hasn't dropped at all...

 

[BillyBob]

Took old air spring, which was suspected faulty, and a big bucket with full of water.

Used air compressor to fill air spring with old line.

Well, no bubbles. Even when I put it to bucket and at the same time I admistired air from compressor. No bubbles. My conclusion is that old spring was working fine.

Is it the valve block? I don’t really have any more ideas. Do you?

 

[Weds]

Have you only changed one air spring? What about the other one..

 

[BillyBob]

Very strange.

Car holds it rear level for one and half hour perfectly. Not any dropping. Checked by measurements.

After one and half hour it starts to fall dramaticly. For first 15 minutes it has lost it’s level on left by 1cm and right 0,5cm. For next 15 minutes left has lost another 1,5cm and right 1cm. Total loss 2,5cm for left in half hour and right 1,5cm.

It did this same thing in warm garage yesterday when I measured.

Why it can hold pressure for 1,5 hours?

I don’t have any other theory that solenoid valves fails to close 100% on some valve, and it starts to fill up compressor and finally after 1,5 hours pressure relief valve opens mechanically and releases pressure and car starts to drop dramatically.

Well, next step is to change solenoid valve block, since it’s very hard to believe that new air spring is faulty since symptomps are the same with old air spring

 

[Will]

I’d have thought if it was dropping down that quickly you’d hear the air hissing out from somewhere? (Weds/Billybob?)

I think there’s a known point on 212s where the air lines can chafe through against the body and leak but you’d expect to see this with the soapy water trick (or hear it hissing!)

Mine only used to drop maybe a few mm overnight, over say 2/3 days you’d notice the tyre would then be under the height of the arch lip (whereas you can fit your hand above the tyre usually). FWIW it doesn’t drop at all now even after a week plus parked up.

My only thoughts regards to the rate yours is sinking would be as the pressure reduces you’ll see it drop more. Eg a tyre may usually be inflated to circa 40psi, but you won’t see it flat with 20psi, but once it gets down to say under 10psi it will drop at a quicker rate as most of the pressure has gone. Likewise in your system, it could be leaking from the moment you park up - but there’s enough pressure there to support it until it loses enough for it to begin dropping. Just a thought.

My logic in your case Billy would be you must have a leak somewhere between the valve block and the spring? So either pipework or the valve itself. Where else can the compressed air go if you’re happy that the springs/bellows are okay?

Good luck

 

[BillyBob]

Replaced new Arnott spring. No more problems. Case closed

 

[steveq]

Hi,

That's great.

So did you replace both sides with new Arnott springs?

 

[SinaW212]

I assume that you have the Self Levelling rear suspension that is standard on E Class Estates.
Your car dropping 3cm isn't much and it could be just the warm air cooling and compressing overnight.

I found that my S212 dropped more noticeably in cold weather. One side was worse than the other but both would have dropped more than 3cm overnight.
After 3 - 5 days of non use the rear of the car was completely down with the tyres under the wheel arches.

The most likely cause is the rear air suspension units starting to fail (as you already have had the air lines checked for leaks).

Unfortunately, no faults will be displayed on Star unless to say that the car is too low.

I replaced both rear suspension units and resolved the problem.

May I ask how much did the whole thing cost pal? I’m going to buy a 2011 W212 Estate and when I went to test drive it, it was quite cold and I noticed the tyres were well under the wheel arches. The seller insisted it’s totally normal especially because there were absolutely no unusual noise coming out of the suspension after and the car went back up quite quickly after start. But I’m still doubtful and thinking about replacing both units. What do you think?

 

[Will]

It depends on which parts you use.

The air springs on mine were about a grand for the parts (genuine MB, pair) plus fitting costs. Fortunately the warranty coughed for it but aftermarket units can be had for about half that, obviously fitting costs will be the same either way although it’s not a difficult job to replace.

So if you want them both replaced, budget £1k ish approx. To me it’s worth doing sooner than later to save excessive wear on the compressor compensating for the leak

 

[Weds]

May I ask how much did the whole thing cost pal? I’m going to buy a 2011 W212 Estate and when I went to test drive it, it was quite cold and I noticed the tyres were well under the wheel arches. The seller insisted it’s totally normal especially because there were absolutely no unusual noise coming out of the suspension after and the car went back up quite quickly after start. But I’m still doubtful and thinking about replacing both units. What do you think?

It's not totally normal, it means there's a leak in the system, Mine now stays up all the time (see post above) I can't remember the last time I heard the compressor running, it used to run for a few minutes every time I started the car.