Hello, I have a 2012 E550 4MATIC.

My front suspension used to drop overnight but now it drops 30 minutes to an hour after not driving it. I eventually got the malfunction error on the dash. I did the soapy water test for leaks and found nothing. My compressor seemed to working fine so I ruled that out. I figured it could have been the solenoid valve block (level control valve) so I replaced it. After replacing it, the ride seemed smoother. (I should add, there are clunking noises and lots of vibration in the wheel. Recently learned it could be bad shock absorbers. Not sure how related it is to the issue) The front did not drop and everything seemed fine and the problem was fixed. 3 days later the front dropped again and the clunking noises came back. It took about a month for the malfunction error to return. Not sure what happened that replacing the valve block completely fixed the issue but only for 3 days.



I bought the iCarsoft MB2 scanner hoping it would help diagnose the issue. It didn’t really help me solve the problem and the codes I looked up, everyone who posted had a different issue. I can share some information I got from it. I’m sure you guys can make more sense of it than me.



Fault Codes

C156784 (Historic): The left front vehicle level is outside the tolerance. There is a signal below permissible limit value

C156984 (Historic): The right front vehicle level is outside the tolerance. There is a signal below permissible limit value

C155664 (Current): The compressed air sensor for system pressure has a malfunction. There is an unreasonable signal. (could this be a compressor issue?)


Other

Compressor locked due to activation time limit: NO

Compressor locked due to on-board electrical system limp-home mode: NO

k67 Airmatic relay: OK

KVD5 Fault: 53336/6058

Signal Voltage of component B22/10 (right rear level sensor): 2137 mV

Signal Voltage of component B22/7 (left rear level sensor): 2824 mV

Signal Voltage of component B22/8 (left front level sensor): 4157 mV

Signal Voltage of component B22/9 (right front level sensor): 2000 mV

Power consumption on axle dampening valve units: both front 259 mA, both rear 298mA. All axle dampening valves are: OK

Pressure in central reservoir: 10.57 bar

Pressure in left front suspension strut: 10.43 bar

Pressure in left rear suspension strut: 10.43 bar

Pressure in right front suspension strut: 10.29 bar

Pressure in right rear suspension strut: 10.29 bar

Level Calibration completed: YES

Lock position: OFF

____

Random note: the rear drops if I leave it on sports mode. It wont drop if I leave it on comfort.

I have read a lot of the threads on here and what I found most was people had leaks in the airbags. I did a leak test on the exposed part of the airbag and found nothing. Also I sat next to it and didn't hear any hissing noise so I am really confused as to what is going on. As for the clunking noise, I figure if the shock absorbers are bad I would have to get new struts anyway. Then I would find out if the problem was in the struts. I hoping to figure out the issue exactly so I don’t buy a part I won’t have to yet. Any info would be great and I appreciate anyone who took the time to read all that.

Thanks.

 

Leaks with Airmatic can come from:

• front air struts
• rear air springs
• nylon air lines
• compression fittings for air lines
• valvebody
• compressor (this one doesn't affect drops in ride unless valvebody is bad as well)

So your job is to start crossing things off the list... I would start by going on a short drive to set the ride height and park it on a relatively flat surface. I'd set it to comfort or sport (you can repeat this test with both) before you set of on your drive and then don't touch it. Park and lock the car and keep the key a good distance away. Measure all four corners, rim lip to fender opening and record. Come back in two hours and record the readings again. Finally let it sit overnight (12 hrs or so) and record the readings a final time.

Now, if you come back in 30 minutes or 2 hrs and the wheel is tucked up in the fender... then go no further. This narrows down which corner or axle has the issue.

As far as checking for leaks, leak detection solution or strong soapy water sprayed on all the air lines and compression fittings to rule them out. Air struts and springs are harder, because they have a protective boot which keeps the solution from getting inside to the actual rubber bladder. Some guys will pull the springs or struts, pressurize them and dunk them into water to check for leaks. On the front struts, take the cap off on the strut tower in the engine bay, and you'll see a coiled air line. Spray all that down with solution to check.

Depending on mileage, it may well be either the struts or rear springs... the rears are common to go about 10/yrs-100k.

You replaced the valve body, so it shouldn't be a source for leaks... unless its being commanded by the module and in which case if there's a leak elsewhere it could facilitate it. As far as the comfort vs. sport drop in height... I suspect its due to the location of the leak on the air bag itself and having the it 'compressed" (lowered in sport mode) either seals it better or worse. I've been told by a MB tech, friend of mine, that sometimes these leaks manifest only while driving as the air bag is exercised due likely to where the failure is.

 

So we can rule out compressor?

I can try and see what happens when I leave the car in sports. I usually drive in comfort and the front will drop within 30 minutes or 2 hours. My rear has only dropped twice (once in sports). I'll try the test and take the measurements.

I have done the soapy water spray on all items listed. Even the air bladder since mine is exposed. I haven't sprayed the rear airbags because that isn't the current issue. Unless somehow the rear can make the front drop??

Also the car is at 93k miles. I know they usually should be replaced around this time but I only want to replace them if I really have to. To me, it is looking like that might be the case but I posted to get more opinions before I spend money on parts.

Thanks.

 

Hi
I read through everything you did - a lot of troubleshooing...

One quick idea...
Since you are getting drops from all 4 corners...
Level up the car and unplug the electrical connector for the valve block so the system cannot self adjust even after the car is off...and see what happens...
Maybe on of your sensors are intermittently bad and the car is adjusting later on?
(JUST DONT DRIVE that way lol)

But if you do that the car should not drop, if it does, then you know its an air leak for sure?

Unless someone else thinks I'm wrong?

Cheers
JPC

 

That's a good idea. I'll give that a go. So basically it's to find out if the issue is between a leak or a sensor?

Also how important is it that the car needs to be on a level surface? My driveway is at a slight slope and I rather not do this in the street. (garage is unavailable)

 

Slope shouldn't be a problem. You still will be able to see which side is dropping
and the distance between ground and fenders will be the same on left and right on the same axle.

 

I apologize to the other posters on this but I just answer this directly without reading other posts as your story is EXACTLY as what I experienced with my 2010 E550.

The car dropping in SPORT mode but not in COMFORT is what baffled me for awhile and I thought it could be a solenoid valve so I replaced the valve block like you did. It did not help as it did not help you either.

The reason car does not drop when left in COMFORT mode is that the spring has enough stroke to build up pressure when car goes down with the other air spring leaking. measure the car height and you will see one side is quite a lot lower than other but the car is still up held by one spring. Believe me, you have a leaking air spring.

For testing the leak with soapy water is impossible as the leak in the spring is inside where the rubber folds over itself.

Get new Arnott air springs (I got mine thru Amazon) and install. Very easy job. Parts cost about $500 for both springs.

If your front is acting up it is most likely the same issue and the clunking sound tells your front shocks are in bad shape. The front struts I could not find other than OEM and I got them from FCP euro for about $1200 each. Again easy job but more pricey parts.

I don't know if the fronts are available for your car from Arnott but for mine they were not.

It seems the Airmatic springs go in about 10 years. Mine did and yours is getting there.

 

Agree with @Arrie regarding it likely being the strut or rear springs.

The valve body doesn't work any differently in sport or comfort mode... its job it to control the ride height at each corner (for sedans) to a target nominal height. Only difference is in sport mode, the target is 10mm lower, IIRC, than comfort. When you park and lock the car the Airmatic module goes to sleep. Thus it can't actively influence ride height... that's why you test for leaks with the car locked. Otherwise the module is awake and it will readjust the ride height if there's enough pressure in the reservoir once you open the door. Now if the module wasn't going to sleep, then another issue.

If the car is dropping in 30 minutes, that's a significant leak... you should hear it. We're assuming its a significant drop. Does it drop every-time you park?

On both our sedan and wagon, the rear end would bottom out overnight. On the wagon, it was only one side dropping and it was a simple leak in the airline running in front of the spare tire tub. Spraying soapy water, immediately you could hear and see bubbling. On the sedan it was both sides... the valve body was leaking back to compressor (so one of solenoids wasn't holding). That in of itself shouldn't cause the drop because the compressor has another set of solenoids, but it needs replacement. I suspect the rear springs are leaking and the primary issue. Spraying soapy water didn't reveal anything on them, nor any of the air lines/connections. I plan to replace them anyway, since their 10yrs/100k on them.

When I finally pull them, I'll cut off the shield and see if I can test them in water for leaks... out of curiosity.

 

No, your right... though if you park and lock the car the valve body "shouldn't" be actively commanded... now if you had a poor connection or short and/or the module was waking up, sure. Certainly a step worth trying.

 

My front would drop regardless of sport or comfort. My rear only dropped twice on sports. Although I have read on a few threads that their rear dropped in cold temperatures and has never dropped since. But I'll be testing that out along with a few other suggestions posted on this thread.

I found Arnott struts for my front but they seem rare. I haven't looked for the rear yet. Just want to make sure for the rear, air bag and springs refer to the same part, right?

 

Yes the front drops every time I park, though I haven't heard anything. Could be a silent one.

 

Rear is separate air spring (bag) and shock. Front is McPherson style spring and shock build as one.

You are wasting your time not doing the inevitable. Your air springs are done. Replace and be worry free another 10 years.

 

Hi all

Locking the car does not actually stop the car from adjusting after you walk away - that's why i suggested unplugging it...my car will auto sense and level the car - I myself park on a sloped driveway and my car adjusts quite a lot after i walk away...

the valve block separates out each corner - so if more than one corner is dropping - then the valve block is bad or something else i wrong unless you had bad luck and had 2 leaks appear at the same time...

Cheers
JPC

 

The system does not "level" the car, i.e horizontal like when using a spirit level... any ride height adjustments after parking and locking can occur because the module/CAN isn't fully asleep. The MB procedure has you park, wait 2 hrs (for any temp-related height change) and you take your initial height reading. Then wait overnight and repeat the measurement.

Parking on a slope won't affect the outcome of the test... unless the OP is parking on a San Fran street. If the wheel is tucked up in the fender, its a leak and not due to valve body / airmatic "leveling" the car.

 

Sorry but I think you are wrong - i can see watch and hear my car adjusting each time park it - on my sloped drive way...
if I park in the garage which is "level" - the car does not adjust...
a quick search I found this- but again I don't want to argue - that is just taking away from the thread..

In some cases, the car will drop itself overnight but not always. If the vehicle is parked on an incline or downhill the raising or lowering may stop working. There are many reasons lead to this malfunction. Mercedes-Benz with airmatic suspension tries to level itself when parked and end up with lowering near to the ground. But the vehicle may try to level itself unsuccessfully when one level sensor is broken, or the rod is bent. This may cause your Mercedes-Benz self-level too high or too low.

I'm sure someone will correct me - I'll just keep thinking its auto leveling...

And a foot note - my airmatic is fine - but a wheel will tuck when on a slope when it does try to level the car...Ill take pictures tomorrow and post if needed

 

To my understanding, if one side drops, the car will drop the other side as well for safety reasons (if malfunction happens mid drive). And it's recommended to replace in pairs. Someone let me know if I'm right or wrong.

 

Not my experience as I've driven, only to find one side much higher than the other. Airmatic only tries to correct the corner which is not at the correct height. If that takes too long you'll get a malfunction (car symbol with arrow pointing up or down).

 

Did you figure this out? I'm having an issue as well. Replaced valve block and front driver's side strut(pinhole leak on backside towards body of car). Forgot car was set for max height (sat for a few months) and started car when swap was done. Passenger side went to max height, but driver's side front went maybe halfway while the rear fender went 1.5" above the tire. Now getting the C155664 error. Pump runs for 4 seconds and cuts off. Let car sit for a few hours, pump ran for around 10 seconds then shut off for a few seconds, then ran for 4 seconds. Shuts off and the malfunction error pops up on the screen. I can clear it and it will only run for 4 seconds. I only have an Autel MaxiCheck to pull codes and look at level sensors.

 

So the compressor only runs for a few seconds at a time, stops, you get airmatic malfunction in cluster and pull code C155664. Correct? How's the vehicle ride height at each corner, does it appear correct, too high, too low? If the car sits overnight, does any corner appear to drop?

C155664 The compressed air sensor for system pressure has a malfunction. There is an implausible signal.

That sensor is built into the valve body, what did you replace it with OE, Arnott, CMT, etc... This won't help you, but with Xentry you could see the pressure (in the reservoir) and when the pump runs does it increase? If you open/release the air line to the tank (reservoir) does the pressure drop?

So is it a pressure issue (too high or not building any) or a sensor issue or a wiring issue (corrosion, short, power/ground). Having access to Xentry, you can run a battery of tests... in this case very helpful I'd say. Whereas with leaks, its not so useful and can be diagnosed DIY.

 

Last thing to add is this Mercedes Bulletin, essentially if your sure no detectible leaks exist in the system (air bag, struts, air lines and compression fittings, valve body, compressor, reservoir)... then Mercedes or indy with Xentry will run a bunch of tests. If they all pass, the software in the Airmatic will be updated.

Similar thread:https://mbworld.org/forums/e-class-w...e-c155664.html

Poster mdreef, did a lot of work and testing, but was still getting C155664... his concern was the frequency at which the compressor was cycling. Same advice given, at the end, Xentry tests and software update may be necessary.

 

I'll try to be as detailed as possible here so this will be alittle long. Car is my brothers. He's currently stationed in Kuwait. He brought the car home with a bad strut( had to keep pulling over so the car would inflate). I couldn't figure out the source of the issue at the time since it wouldn't inflate at all so I replaced the valve body( part came from mbpartsdirect.com). After replacing it, the car would rise off the floor like it should, but then it would drop after a day or 2(front first). So once I had time to work on it(along with a busted inner cv boot smh) I finally found the leak(driver front). Ordered the wrong part(Summit racing) and didn't realize it till taking the old one out so the car sat on jackstands for a month or 2 waiting on the new one(arnott AS-3238. Had to send the wrong one back to be exchanged plus I work a good amount of OT). Stands on front, not rear. Never turned car on while on stands. Put new one in a few days ago. Took car off stands and started it. Note, in this time the car was on stands, I've randomly used the battery charger on the battery. I believe it may have went dead once or twice. The button in the car was set for max height(I was using it to troubleshoot the leak). After starting, the pump ran as normal. The passenger side inflated fully, but the driver side did not. Driver side did inflate some, but the rear is still low. After awhile the malfunction error popped on the screen. Cleared it(after the pump sat for a few so it could cool), and it ran for 4 seconds and cut off. Let the car sit for a few hours then started it again. Pump ran for around 14 seconds then cut off. Malfunction error popped on screen again. Cleared it, and pump only ran for 4 seconds. Measured gap at drivers rear wheel from tire to fender and it's 1.5". Let car sit for about 2 days and went in there earlier to start it. As soon as it started, I pushed the max height button to turn it off. Heard some air get released, but still lopsided. Let it run for a couple minutes and took pics of values attached( benz 1, 2 and 3). Said "screw it" and hit max height button again. Felt the car rise in the front, but the rear didn't change. Malfunction error popped up again. I didn't time how long the pump ran, but it was well longer than 4 seconds. Benz4 is the final values I took. I'm limited on what I can see/do with the scanner I have. The driver's rear is still at 1.5" gap. I'm tempted to try disconnecting the battery for awhile and see what that does. Sorry about the big and double set of pics. I couldn't figure out how to delete them.

benz1

benz2

benz3

benz4


4

 

You never posted year and mileage... some will say, the car is at an age that all the struts and air springs should be replaced as it only a matter of time before they start failing. The rears are very common failure. I wouldn't disagree if you plan to keep the car for a while and it might reduce the amount of troubleshooting and messing around. I certainly would have replaced both struts, even if only 1 had a leak given the likely age of the car.


The scan tool data, suggests the left rear doesn't really respond and is the lowest corner. I'd check whether the ride height sensors at all four corners are responding. This could be done with the scan tool hooked up and jacking up (via jack pad) each corner. The expectation would be the value (example: -30 mm) would increase as you raise the corner, i.e. -30, -25, -15, 0, 5, 10, etc... and then decrease as you lower. Obviously the other corners will change as well, but focus on the one your lifting. Repeat for all corners. That should provide a rough idea that the sensors are working.

The next question would be, why doesn't the left rear respond *if* the sensor is working...

* is the ride height calibration that far off and airmatic is not trying to level the car?
* is the valve body not operating correctly?
* is there that massive of a leak, it can't raise that corner?

For the left rear corner that isn't raising, you could disconnect the line at the valve body, using shop air with a rubber-tipped nozzle, carefully apply pressure to the air line and see if you can get it to rise.

Disconnecting the battery for 10 minutes... okay. It can't hurt, but wouldn't expect any change in behavior.

 

I'm sorry, it's a 2010 E550 with 140k miles so it's probably past due for replacements. I didn't have much time, but I did the four corners with the jack and the sensors responded accordingly. Thanks for all the help so far. I'll have to see what route he wants to take and how much he wants to dump into this car.

 

So the left rear reads -30 mm to -36 mm level but you still have 1 1/2" between tire and fender. I think your left rear level sensor is bad or reading wrong due to off calibration or the sensing arm is broken or has moved as with -30 mm you should not have 1 1/2" between tire and fender.

 

My air struts just arrived. I will be replacing them tomorrow and will post an update. We got the same error code but we may have a different issue. Does your scanner tool have the ability to check the compressor?