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New to the forum and I am going to try to explain this the best that I can. I have a 2008 GL320 with around 130k. I had all four air struts replaced in august of 2019. everything was going great until about 6 months ago and I started getting the "compressor cooling down message" all struts were holding air and nothing was sagging, it just would not allow me to raise it to the "raised level" so I replaced the compressor and that seemed to fix it for a few months. then I started getting the message again.
after doing some research I decided to replace the valve block, thinking that maybe that was what was wrong originally, causing the compressor to go out. so I replaced the valve block and the compressor again and once again seemed to fix my problem.
then the other morning I came out and noticed my front end was almost completely bottomed out. so I got the jack out and jacked up the front end to spray some soapy solution on the struts to check for leaks. no leaks that I could see. when I lowered the back back down off the jacks, it was back to normal ride height. it seems that taking pressure off by jacking it up allowed it to raise back to normal ride height.
I then pressed the raise button and raised it to the "raised level" and let it stay there for a few hours. came back out and it was still holding that level. tried the soapy solution again and could not see or hear any leaks in the struts.
I then went to lower it back down to normal level and this is where things get strange. it took over 30 minutes but eventually the front lowered all the way to bottomed out, like I have about a inch between top of tire and wheel well. BUT the rear end did not lower back down at all. it is still at the raised level. car said on the dash that it was at lowered level. I pressed the raise button again and it raise the front to about 3 inches of clearance but did not affect the back, and then said on the dash "raised level"
I am at a loss as to what this could be. car rides very bouncy. any ideas? could it be ride level sensors? would this be all four sensors going out?
could it be a compressor relay? I replaced the relay the first time I replaced the compressor but not the second time I replaced it. also it should be noted that I can hear the compressor come on initially when I cut the car on and for a few seconds when I try to raise it but after that I cannot hear it. I am not getting any airmatic malfunction messages and I am not getting a compressor cooling down message.
it seems like the car things it is raising it and lowering it just fine but nothing is really happening. my first thought is the front struts had went out again, but I have a hard time believing both went out at the same time, and that would not explain why the rear end isn't lowering back down. lastly all 4 struts have about 15k on them.
New to the forum and I am going to try to explain this the best that I can. I have a 2008 GL320 with around 130k. I had all four air struts replaced in august of 2019. everything was going great until about 6 months ago and I started getting the "compressor cooling down message" all struts were holding air and nothing was sagging, it just would not allow me to raise it to the "raised level" so I replaced the compressor and that seemed to fix it for a few months. then I started getting the message again.
after doing some research I decided to replace the valve block, thinking that maybe that was what was wrong originally, causing the compressor to go out. so I replaced the valve block and the compressor again and once again seemed to fix my problem.
then the other morning I came out and noticed my front end was almost completely bottomed out. so I got the jack out and jacked up the front end to spray some soapy solution on the struts to check for leaks. no leaks that I could see. when I lowered the back back down off the jacks, it was back to normal ride height. it seems that taking pressure off by jacking it up allowed it to raise back to normal ride height.
I then pressed the raise button and raised it to the "raised level" and let it stay there for a few hours. came back out and it was still holding that level. tried the soapy solution again and could not see or hear any leaks in the struts.
I then went to lower it back down to normal level and this is where things get strange. it took over 30 minutes but eventually the front lowered all the way to bottomed out, like I have about a inch between top of tire and wheel well. BUT the rear end did not lower back down at all. it is still at the raised level. car said on the dash that it was at lowered level. I pressed the raise button again and it raise the front to about 3 inches of clearance but did not affect the back, and then said on the dash "raised level"
I am at a loss as to what this could be. car rides very bouncy. any ideas? could it be ride level sensors? would this be all four sensors going out?
could it be a compressor relay? I replaced the relay the first time I replaced the compressor but not the second time I replaced it. also it should be noted that I can hear the compressor come on initially when I cut the car on and for a few seconds when I try to raise it but after that I cannot hear it. I am not getting any airmatic malfunction messages and I am not getting a compressor cooling down message.
it seems like the car things it is raising it and lowering it just fine but nothing is really happening. my first thought is the front struts had went out again, but I have a hard time believing both went out at the same time, and that would not explain why the rear end isn't lowering back down. lastly all 4 struts have about 15k on them.
What about the level sensors? Check if they are not jammed or stuck. The joints where the arm and the sensor are connected could corrodeand collect dirt. The joints should be moving freely when moved by hand. I would remove them, clean, grease and reinstall.
What about the level sensors? Check if they are not jammed or stuck. The joints where the arm and the sensor are connected could corrodeand collect dirt. The joints should be moving freely when moved by hand. I would remove them, clean, grease and reinstall.
And welcome to the forum!
I forgot to mention, I did replace the front two sensors when I replaced the compressor and valve block. I did not replace the arm that connects to the sensors. but sensors seem to be moving fine. when I parked it last night I raised it to raised height and it held that level all night long without dropping. when I got to work this morning, I went to lower it and sure enough it lowered on the front to where it was bottomed out and I didn't seem to lower the back much if at all.
when replacing the sensors do you need to have the ride height recalibrated?
Its yer bags. Search the forum for like kind symptoms.
Compressor cooling down usually also means that needs replaced - it's burning out from trying to pressurize earth's atmosphere.
I am no longer getting the compressor cooling down message. that was about 6 months ago and I replaced the compressor, valve block, and the front sensors and that seemed to fix everything temporarily.
also its not just one side sagging or one corner. the front is sagging and the rear is staying at "raised level"
I am no longer getting the compressor cooling down message. that was about 6 months ago and I replaced the compressor, valve block, and the front sensors and that seemed to fix everything temporarily.
also its not just one side sagging or one corner. the front is sagging and the rear is staying at "raised level"
I would take that symptom as an indicator that one or both of your front bags have a leak, and your fully functioning level sensors are doing their job trying to keep the car level.
I would take that symptom as an indicator that one or both of your front bags have a leak, and your fully functioning level sensors are doing their job trying to keep the car level.
if thats the case then why is the rear staying in the raised position when I try to lower it? also if it was a leak, wouldn't the level drop over time? it will stay at the raised level with no problems or no leaking. I am also not hearing any leaking air, or getting any malfunction messages.
when it bottoms out on the front end I also do not hear the compressor running. it seems that if it was bottomed out, and there was a leak in the bags the compressor would continue to try and inflate the front bags to raise them to proper ride level, but would ultimately not be able to and then would throw either a malfunction or compressor cooling down.
I had a leak in the front driver last summer and replaced all four at that time. this is not showing the same symptoms as it did when I had that leak. it seems like the car things its level, but its not.
I would take that symptom as an indicator that one or both of your front bags have a leak, and your fully functioning level sensors are doing their job trying to keep the car level.
also not ruling out that it could be the bags, that just doesn't seem like it is. really just talking through symptoms and problems. thanks for the replies.
I forgot to mention, I did replace the front two sensors when I replaced the compressor and valve block. I did not replace the arm that connects to the sensors. but sensors seem to be moving fine. when I parked it last night I raised it to raised height and it held that level all night long without dropping. when I got to work this morning, I went to lower it and sure enough it lowered on the front to where it was bottomed out and I didn't seem to lower the back much if at all.
when replacing the sensors do you need to have the ride height recalibrated?
Not sure if sensor recalibration is necessary. From limited personal experience, the front and rear seem to be affected independently. If one or both your front bags are a problem, the rear wouldn't necessarily exhibit the same symptoms and vice versa.
In terms of why the rear doesn't drop as you expect when you lower the suspension, does it move when you raise it? I am assuming you are using the sport/comfort settings of ADS.
Not sure if sensor recalibration is necessary. From limited personal experience, the front and rear seem to be affected independently. If one or both your front bags are a problem, the rear wouldn't necessarily exhibit the same symptoms and vice versa.
In terms of why the rear doesn't drop as you expect when you lower the suspension, does it move when you raise it? I am assuming you are using the sport/comfort settings of ADS.
as far as I can tell it doesn’t seem to be moving much at all. When the front is bottomed out the rear looks to be raised. When the front is raised the rear looks to be about normal. I’m not sure if that means it’s moving, or if the movement from the front is affecting the height of the rear
as far as I can tell it doesn’t seem to be moving much at all. When the front is bottomed out the rear looks to be raised. When the front is raised the rear looks to be about normal. I’m not sure if that means it’s moving, or if the movement from the front is affecting the height of the rear
I would suggest measuring with tape, ground to fender lip on the same surface with the front up and bottomed out sometimes the difference in height may not be visible to the eye easily.
Update, it has held “raised level” for the past day and a half. Haven’t had to drive it so I left it at that level. It did not drop the time it was raised. I went to drive to today and pressed the button to lower it lowered fine and showed the Airmatic level but this is the level it’s at
if thats the case then why is the rear staying in the raised position when I try to lower it? also if it was a leak, wouldn't the level drop over time? it will stay at the raised level with no problems or no leaking. I am also not hearing any leaking air, or getting any malfunction messages.
when it bottoms out on the front end I also do not hear the compressor running. it seems that if it was bottomed out, and there was a leak in the bags the compressor would continue to try and inflate the front bags to raise them to proper ride level, but would ultimately not be able to and then would throw either a malfunction or compressor cooling down.
I had a leak in the front driver last summer and replaced all four at that time. this is not showing the same symptoms as it did when I had that leak. it seems like the car things its level, but its not.
ok I missed that you replaced all four bags. HVe you hooked it up to a star/das tool to do a real-time readout of your level sensors?
have you had it calibrated? That’s also a Star/das function I’d do first.
it might be your sensors then. Something - your front sensors possibly - isn’t telling the valve block to distribute air to the front bags.
Last edited by Max Blast; Aug 15, 2020 at 08:28 PM.
ok I missed that you replaced all four bags. HVe you hooked it up to a star/das tool to do a real-time readout of your level sensors?
have you had it calibrated? That’s also a Star/das function I’d do first.
it might be your sensors then. Something - your front sensors possibly - isn’t telling the valve block to distribute air to the front bags.
I have not had them read or recalibrated. As I am somewhat new to Mercedes in general I am not familiar with the star/das tool. I’m assuming that’s a type of code reader? Is that something that I can purchase or does that type reading have to be done a dealership/Mercedes shop?
I am also think it’s sensors. Because it will raise and hold level no problem. When it lowers it goes straight to bottomed out. It doesn’t lower to correct level and then leak down to bottomed out.
The symptoms you have can happen basically in three cases: faulty valve block, faulty sensors and dead airstruts. You do need to find an indy mercedes shop and get your car scanned with Star Diagnosis (mercedes dealership scanning tool). I will show all your struts and reservoir pressures and if your car lose them or not, level sensor readings etc.
Been a while since I updated this. But it has been in the shop, a independent MB shop. They have checked EVERYTHING. Found a small crack in the valve block and replaced it. Recalibrated all level sensors. Bags are good. Lines are good. Pump is good. Car still will not level up. Mechanic says it’s acting like it thinks it’s level but it isn’t. Could this be a computer problem? Like does that need to be reset?
So after the vlave block replacement the car is still uneven the same as before with the old block Wiring? Or is it leaning to another corner? How about the wiring harnesses/plugs? Check the harness for each sensor and make sure the connections are clean, no chafing of wires. You could also test voltage to each sensor. Or the shop should be able to.
So after the vlave block replacement the car is still uneven the same as before with the old block Wiring? Or is it leaning to another corner? How about the wiring harnesses/plugs? Check the harness for each sensor and make sure the connections are clean, no chafing of wires. You could also test voltage to each sensor. Or the shop should be able to.
yes after new valve block the car is same as before. They check all sensors and wiring to them. Only thing they haven’t checked yet, and they are doing it tomorrow, is the pump relay. Could that potentially be the issue?
I don't think the relay would have any bearing on the uneven leveling of the car. It would affect the compressor working effectively or not working at all. It seems like in your case the bags are just not inflating properly to keep the vehicle level.
I would be curious to know that the shop has checked, visually at least, the connections of the sensor plugs, and not just unplugged/replugged them to the sensors. If they have water intrusion and corrosion, they need to be cleaned, as well as the sensors' pins inspected and cleaned.
I don't think the relay would have any bearing on the uneven leveling of the car. It would affect the compressor working effectively or not working at all. It seems like in your case the bags are just not inflating properly to keep the vehicle level.
I would be curious to know that the shop has checked, visually at least, the connections of the sensor plugs, and not just unplugged/replugged them to the sensors. If they have water intrusion and corrosion, they need to be cleaned, as well as the sensors' pins inspected and cleaned.
to my knowledge they have checked the sensors. All sensors are reading as they should.
The shop determined it was a crack in the valve block and both from level sensors were bad. They replaced that and said they had trouble getting it to raise back up so they have to do that manually (don’t know exactly what that means, I’m assuming they had to inflate each bag individually)
anyways everything worked great for the past two weeks. My wife was out driving it last night and a malfunction message popped back up. It still road level and stayed level all night. She took it to work and while on her lunch break the malfunction message came back up. I told her to see if it would raise. She hit the button and after a few minutes it said compressor cooling down. She parked it for lunch and came back out and it had lowered slightly, probabaly about a inch lower than normal.
im guessing this is now the compressor? My thoughts are if they valve block had a crack, the compressor had been working overtime and basically wore itself out. After having the valve block fixed the compressor has now bit the dust?
Yes, because it is now working against resistance, which your leaky system didn't previously provide.
yes the compressor has probabaly bit the dust?
Meaning when the valve block was cracked there was no resistance on the compressor providing air. Now that the block is fixed there is resistance It basically doesn’t have enough juice left to work
The only way to determine if a compressor is really shot is to test it - it must put out 16 bar in 40 seconds. That test is available under the DAS -> Chassis -> Airmatic test menu if you have an MB code reader.
If it doesn't pass the test, it is toast. A new compressor should build that kind of pressure in 1-2 seconds. I had one that tested fine but took 10-12 seconds to build 16 bar - because one of the cap screws had failed. See my threads on that particular one.
Also do a visual and aural inspection of your compressor. You can do that by turning the wheels full right and removing the front half of the inner wheel well liner of the right front wheel.
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