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In the last few months I have replaced my right front strut and air spring assembly as it was making a rattling noise, then the front left as it was leaking, then both of the rear air springs as at least one of them was leaking. So just when I think that my suspension troubles should be solved for a while, I notice that when I come out to the vehicle first thing in the morning, it appears to be in a raised position. I start it up, and I get the message on the dash "being lowered," and I can see the raise/lower button flashing as it sinks.
I scanned the suspension, but only found a line leak indication, which was left over from the leaking rear springs. I replaced the compressor and valve block about 7 years (and 47k miles) ago, as I was getting a variety of mysterious and eratic sinking of the vehicle on various corners and an indication that the compressor was shot.
So I suspect that the valve block is again the culprit, and that pressure is being allowed to leak into all springs overnight, causing it to rise. Since no command to rise has been sent, it sinks back down each morning when started.
I would be curious to see measurements. Meaning, measure the distance between the top of the tire and the fender at all four corners in the normal position immediately when you park it after driving, then raise the suspension and measure again, then lower it back to the normal position and measure a third time. The third measurement should match the first I think. Then measure again in the morning to see if it actually raises overnight and by how much. (I'm an engineer and like data, can you tell ha ha). Maybe it's actually slowly raising a little while driving (sensor issue?) and so the first measurement will be different than the third measurement. Or maybe the fourth measurement (morning) will be in between the first and second to support your overnight-raising theory. I will be curious to find out what's going on, please post a follow-up.
There’s something commanding your car to rise when it’s parked - or - your valve block is leaking as you say, but it can’t leak all four corners.
first, rule out, stuck button.
Then scan your front Sam/dashboard for signal to and from that button.
But this one is weird for sure because you’re not supposed to rise with the engine off. And you’re also prevented from lowering the vehicle with any door open.
Last edited by Max Blast; Jun 4, 2025 at 06:49 PM.
Well, of course this morning I went out and it was at its normal ride height. I have recorded the normal ride height, height with it intentionally raised, and the return-to-normal height--will share when I have the mysterious overnight increased height for comparison. Fiddled with the button and can't see that it is in any way stuck. My logic would be that if the button was stuck, or accidentally pushed, then I might find the vehicle raised in the morning, but it would not immediately lower itself, it would just stay raised until told to lower, or it lowers automatically because it reaches the speed threshold. I'm imagining that there is positive pressure in the reservoir, and overnight it leaks into all 4 bags causing it to rise. This would assume a lot of leaking valves and seems fairly unlikely that it would appear so consistent. It will be interesting to see if it rises even higher than "normal" raised position but will have to wait for that to happen again.
So here is the latest: The mysterious rising continues. Not every day, but sometimes, quite rapidly while I am in a store for 30 minutes or so. So far, the amount of rise can vary, and has not exceeded the measurement of the completely Raised position, but the vehicle gets driven every day, so maybe the thing to do would be to park it for a couple of days and see if it actually rises higher than the Raised position. Sometimes, only one side of the vehicle is elevated, while the other side is still at standard height. I have a replacement valve block in hand, so my next action will probably be to swap it out and see if that solves the mystery.
I believe the ride height sensors are doing their job--when the vehicle is mysteriously in a raised position, as soon as it is started, it checks the ride height sensors, perceives that the vehicle is elevated, and immediately goes into "lowering" mode until it is back at normal ride height.
Well, it has been a while, so here is the latest in the mystery: The random rising issue has continued. The only error code I get (using an Autel code reader) is an issue with it taking too long to fill the reservoir (which I usually find to be a problem with a worn out compressor). So I changed out the valve block (with an after-market unit) today. After doing so, had to go through several iterations in getting the suspension to fully inflate. I did get one error reading that one of the ride height sensors was giving an implausible value (but that went away and never returned). So now that the system has reinflated, I get no error codes, yet my rear suspension is riding at least 1/2" lower than it used to. In addition, if I hit the ride height button to raise the ride height, nothing happens. Surprisingly, no error codes are being coded. Any ideas?
Played with it some more today, and it magically started behaving properly again. Was able to raise and lower it, got corner heights back to what looks normal. I took it for a drive, and am now randomly getting the "Reservoir taking too long to fill" malfunction, so I'm guessing a new compressor is the next step.
I have no expertise in the automatic system, however I have had my 2012 GL450 for just over I year. It had been parked on a few used car lots for about 8 months prior to being sold to me with very little movement. ........So to the issue......
Initially the vehicle would max out the left front corner when sitting overnight it would also cause the right rear corner to sit as the lowest corner. The truck would air up with engine running but the front left conner would remain higher then the rest. After reading and getting a good understanding of the self leveling sensors I found all of mine to be in some degree of rusted frozen. I worked on the front two lever arms to lube up and free their movement. At that point when ever I shut off the car I would manipulate that front left sensor level arm until the valve block would react and lower the front end. After a week of that the front end settled down and would self level when the car was shut off its own. I have not spent enough time under the rear to free those two levelling sensors up for fear the car will lower itself while I am under there so next time I have it on a lift I will really get after them. The right rear will still sit the lowest over night but not by much and truck airs up right way when started.
My thoughts are the the sensors self leveling action take place with engine and power off. As well as being active when manually raising or lowering the suspension. But move to some sort of pre set level when the engine is running based on speed and other conditions. I intend to free up my two rear level arms then consider replacing all four sensors and move from the original plastic level arms to a metal adjustable type next spring.
It was pretty cheap for a tool that is bi-directional with a Benz. (I've been looking for something "cheapish" for a while)
I read the Airmatic system, recalibrated the height sensors and set a new ride height. Did this a few hours ago, I'll see if the settings stay saved in the ECU over the next few days.
Nice. I would be interested in your review of the scanner overall for the Benz.
I use mine all the time...it does everything I have ever needed it to do. The other day I tried to use it to reset the service light on my Sprinter 3500 and it would not do it - gave me instructions on how to do it on the dash (that also did not work) some of the buttons it said to hit are not there...
It was pretty cheap for a tool that is bi-directional with a Benz. (I've been looking for something "cheapish" for a while)
I read the Airmatic system, recalibrated the height sensors and set a new ride height. Did this a few hours ago, I'll see if the settings stay saved in the ECU over the next few days.
Wel back to updates to the original thread: I replaced the compressor and initially got the "reservoir taking too long to fill" malfunction, but haven't seen it in a while. I also seemingly suddenly notice that when I come out to the locked vehicle and unlock the doors (I assume the suspension automatically lowers a little bit to facilitate entry), I hear a hissing sound from the front end. Is this the normal sound of air being vented to reduce the suspension height, or should that air be sent to the reservoir, and I am hearing a leak?
Wel back to updates to the original thread: I replaced the compressor and initially got the "reservoir taking too long to fill" malfunction, but haven't seen it in a while. I also seemingly suddenly notice that when I come out to the locked vehicle and unlock the doors (I assume the suspension automatically lowers a little bit to facilitate entry), I hear a hissing sound from the front end. Is this the normal sound of air being vented to reduce the suspension height, or should that air be sent to the reservoir, and I am hearing a leak?
Has the rising stopped?’I have been working on my GL trying to find out why the compressor is running too much compared to my other mb air suspension vehicles. I couldn’t find this writeup for a x-164 but this writeup sure opened my eyes for all that the control module under the driver foot well does and all the signals going to it. definitely worth the read.
at the very end of article
“A parked vehicle is "woken up" before the engine is started. That is to say, the AIRmatic with ADS control module receives signals from the door contact switches, the trunk switch and infrared remote control indicating that the driver may soon start the engine and drive the vehicle. The current vehicle level is checked immediately and corrected if required. The vehicle level at the front axle is considered to be critical, for instance, if the full wheel angle can no longer be guaranteed. In this case a message appears on the multifunction display in the instrument cluster to warn the driver: "Stop car too low". If the control module is woken (for example by opening one of the doors), there follows a period of spare time before the driver actually starts the engine during which the vehicle level is corrected. This reduces the waiting time required to correct the vehicle level and the vehicle is ready for driving more promptly. Pressure in the main reservoir is used to raise the stationary vehicle. The compressor is only used if the pressure reservoir is empty. It must be ensured that the battery voltage is sufficient to then start the engine.”
Things seem to be back to normal. The front struts and airbags have been replaced, as well as the valve block and the compressor. Now it can sit for several days and neither rise nor sink. Normal. I did get just the one warning about the compressor taking too long to fill the reservoir right after I replaced the compressor, but I am guessing that it had something to do with needing to fill the reservoir after breaking the lines--haven't seen it since (knock on wood). I'm guessing that when I have seen the "reservoir taking too long to fill" warnings, it is because the compressor is worn out from constantly filling leaking airbags.
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