Another Airmatic thread---but with a twist
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Joined: May 2013
Posts: 81
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From: Houston, TX
'98 E320 and '08 GL320
Another Airmatic thread---but with a twist
Last June, I had leaking air springs that inevitably led to replacing all four. My compressor was taking too long to fill the system, so that was replaced as well. Then I started getting wonky thing like only the front air springs deflating, which I had seen before, so I replaced the valve block. This was the third time I have replaced pretty much the entire system, so I feel like I have a good handle on trouble shooting these things.
Jump to a week or so ago, when the front two springs deflated inexplicably. Trouble shot with my scanner (not bi-directional or as good as I would like) and was misled to believe that it was a failed ride height sensor. Replaced both of the front ones and still get an error: Line Leak. So after further troubleshooting, I find that I never hear the compressor running. If I come out first thing in the morning, and start and try to raise the vehicle, the light will flash for a while, and then I get the "Malfunction" message on the dash. But no indication the compressor is active. I have tried swapping out the compressor with an old one, and no difference. I've checked/replaced the fuse and the relay, and nothing. Checked everywhere for leaks, but found nothing.
The most confusing part of the current situation is that it appears that the system is not sending power to the compressor at all, as if it is in a "protective" mode, yet, when I scan after clearing the line leak code, nothing new comes up. My scanner doesn't show any pressures, just the various codes, and the feedback from the ride height sensors.
Thanks in advance!
Jump to a week or so ago, when the front two springs deflated inexplicably. Trouble shot with my scanner (not bi-directional or as good as I would like) and was misled to believe that it was a failed ride height sensor. Replaced both of the front ones and still get an error: Line Leak. So after further troubleshooting, I find that I never hear the compressor running. If I come out first thing in the morning, and start and try to raise the vehicle, the light will flash for a while, and then I get the "Malfunction" message on the dash. But no indication the compressor is active. I have tried swapping out the compressor with an old one, and no difference. I've checked/replaced the fuse and the relay, and nothing. Checked everywhere for leaks, but found nothing.
The most confusing part of the current situation is that it appears that the system is not sending power to the compressor at all, as if it is in a "protective" mode, yet, when I scan after clearing the line leak code, nothing new comes up. My scanner doesn't show any pressures, just the various codes, and the feedback from the ride height sensors.
Thanks in advance!
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From: Seattle, WA
SL500
Did you check Both fuses? There is the Big 40 amp fuse in the engine compartment fuses box. Then in the rear luggage compartment fuse box there is another 15 amp fuse for the Airmatic control unit (Fuse location #32). If it seems like the compressor is getting no signal, then I'd suspect the fuse in the rear for the control unit.
Last edited by Aussiesuede; Apr 28, 2026 at 08:54 PM.
Thread Starter
Member
Joined: May 2013
Posts: 81
Likes: 8
From: Houston, TX
'98 E320 and '08 GL320
I hadn't checked the 15a fuse in the rear, but it is solid. The 40a fuse is also not welded in place. So this morning when I fire up the vehicle, the raising/lowering button flashes its light for a while, the compressor does not hum, and eventually, I get the "malfunction" message on the dash. When I check the codes, sometimes I get the "line leak" message, sometimes no code at all.
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From: Emmett, ID, USA
2007 GL450
The self diagnostics are generally a bit lame. For example, the system notices that it is taking too long to raise the central reservoir pressure and concludes there must be a leak - because there is no way the pump could be malfunctioning, right?
Have you verified that the front air springs are not leaking? When replacing mine recently, we found that over-torquing the compression nut on the air line can squeeze the o-ring out of position. Check for leaks using soapy water.
Regarding the "leaky line" error: This could be due to a malfunctioning compressor relay. The system apparently does not sense whether the compressor is actually running; it only knows that voltage is being applied to the relay, not that the relay is applying voltage to the compressor or that the compressor is running. (At least, this is my understanding. Don't quote me.) Try replacing the relay; it's a cheap diagnostic.
The relays are also dangerous. There is a diode inside them that shunts excess voltage, created when the pump motor is turned off, to ground. If the diode shorts out internally, it will route excess current through the fuse block circuit board traces. Failure here would cause all sorts of additional problems, so seems unlikely in your situation, but it couldn't hurt to lift the engine compartment fuse-and-relay board and look at the traces underneath.
Also, please tell the manufacturers of your various replaced components. Some low-budget valve blocks simply don't work at all. Cheap compressors can fail very quickly.
Have you verified that the front air springs are not leaking? When replacing mine recently, we found that over-torquing the compression nut on the air line can squeeze the o-ring out of position. Check for leaks using soapy water.
Regarding the "leaky line" error: This could be due to a malfunctioning compressor relay. The system apparently does not sense whether the compressor is actually running; it only knows that voltage is being applied to the relay, not that the relay is applying voltage to the compressor or that the compressor is running. (At least, this is my understanding. Don't quote me.) Try replacing the relay; it's a cheap diagnostic.
The relays are also dangerous. There is a diode inside them that shunts excess voltage, created when the pump motor is turned off, to ground. If the diode shorts out internally, it will route excess current through the fuse block circuit board traces. Failure here would cause all sorts of additional problems, so seems unlikely in your situation, but it couldn't hurt to lift the engine compartment fuse-and-relay board and look at the traces underneath.
Also, please tell the manufacturers of your various replaced components. Some low-budget valve blocks simply don't work at all. Cheap compressors can fail very quickly.
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Joined: May 2013
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From: Houston, TX
'98 E320 and '08 GL320
Literally all of the air bags, the compressor and the valve block were replaced last June. Everything seemed to be holding fine, then one day a couple of weeks ago, I pulled the vehicle out of the driveway, and then backed it back in, and the next morning the front end had deflated. One of the error codes at the time referred to an implausible signal from one of the front ride height sensors, and the value of that one did seem out of whack. So I replaced both of them. I have been working on replacing the steering rack for the last couple of weeks, and now that that is done, I have turned my attention back to the air suspension. So far, I have done the following:
- Replaced the relay, and checked the front and rear fuses
- replaced the valve block
- swapped out the current compressor with an old "worn out" one, just to test and see if it runs...no change.
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
Oh, one other question. Where is the car? For instance, I did my bags, lines, shocks, compressor and solenoid. Freaked me out that when it was on a jack the pump never started.
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From: Emmett, ID, USA
2007 GL450
Do the basic diagnostics rather than trying to divine what is going on via your scan tool. I beat my head against the wall for weeks because I couldn't understand the diagnostic information, and couldn't believe that a new Arnott pump would fail after 20k miles. So do the soapy water test on everything you disturbed while replacing, and consider whether you might have installed new but low quality parts. There's no shame in that; we've all refused to believe that new parts could be bad. In large part due to Chinesium ingredients (Arnott pump Made in China), "Nothing works anymore." We've got guys, myself included, that installed brand new, supposedly high quality, CV axles that are going clink clank clunk. It's maddening.
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From: Albuquerque
'10 CL550, '12 GL550
it doesn’t and that’s normal.
confess I’ve never jacked up a wheel with the ignition on.
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From: Houston, TX
'98 E320 and '08 GL320
Alrighty then, I seem to be making some progress. First thing this morning I unplugged the compressor electrical connections, and found that I had voltage there. Swapped in the old compressor (again) and it hummed. So I removed the current (less than a year old) compressor and put the old (worn) one back in. So I figure what was happening when I tried all this earlier is that I had already tried to make the vehicle rise, the system had already gone into error/system protection mode, and hence no juice to the compressor. Somehow in the process of all of this, the compressor motor failed.
All is not well yet, though. Now when I start the car up, the compressor hums for a while then eventually stops. I then get the "Malfunction" error, and when I read the codes, it now has only the "Suspension Strut is implausible". It still doesn't rise, so either my old worn compressor isn't putting out enough air, or there is still a massive leak. Still scratching my head. I figure a new compressor is the next step.
All is not well yet, though. Now when I start the car up, the compressor hums for a while then eventually stops. I then get the "Malfunction" error, and when I read the codes, it now has only the "Suspension Strut is implausible". It still doesn't rise, so either my old worn compressor isn't putting out enough air, or there is still a massive leak. Still scratching my head. I figure a new compressor is the next step.
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
I have thus far had great results from these guys....
https://rebuildmastertech.com/merced...-ads-airmatic/
https://rebuildmastertech.com/merced...-ads-airmatic/
Thread Starter
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Joined: May 2013
Posts: 81
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From: Houston, TX
'98 E320 and '08 GL320
I have thus far had great results from these guys....
https://rebuildmastertech.com/merced...-ads-airmatic/
https://rebuildmastertech.com/merced...-ads-airmatic/
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From: Emmett, ID, USA
2007 GL450
Things may have changed in the last few years, but the go-to compressor always was AMK. Nobody reported good results with any other make.
You need to clear the error codes before the suspension will resume normal operation. It will helpfully avoid running the compressor when it thinks the system is leaking. The codes might self-clear with drive cycles, but it is much quicker and safer to do it manually.
If you have the means and inclination, a bidirectional scan tool is highly recommended. For example, accessing the Airmatic module, you'd be able to raise and lower individual corners on the vehicle. This might have saved you some pain.
My general impression that Autel is on the leading edge of third party scan tools - my MP808 seems quite solid - but there may be others.
No-name parts are hit-or-miss. I installed a valve block that was non functional out of the box. TPMS lasted from one to five years. But my no-name thermostat has held up faithfully for 50k miles now. To be safe, I now only install the best, near-OEM, parts - but still that is not a guarantee I won't be found crying in the garage.
You need to clear the error codes before the suspension will resume normal operation. It will helpfully avoid running the compressor when it thinks the system is leaking. The codes might self-clear with drive cycles, but it is much quicker and safer to do it manually.
If you have the means and inclination, a bidirectional scan tool is highly recommended. For example, accessing the Airmatic module, you'd be able to raise and lower individual corners on the vehicle. This might have saved you some pain.
My general impression that Autel is on the leading edge of third party scan tools - my MP808 seems quite solid - but there may be others.
No-name parts are hit-or-miss. I installed a valve block that was non functional out of the box. TPMS lasted from one to five years. But my no-name thermostat has held up faithfully for 50k miles now. To be safe, I now only install the best, near-OEM, parts - but still that is not a guarantee I won't be found crying in the garage.
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From: Emmett, ID, USA
2007 GL450
P.S. Arnott sank to second- or thir-tier status. They used to be famous for their lifetime no-questions-asked warranty, but that no longer holds: It's now "lifetime, excluding wear, such as aging (dry rot) of the air springs, causing leakage", as I found out when I called about my leaking struts. Also, one member here looked closely at the rear air springs and discovered their pressure rating was significantly lower than the same product from Bilstein. Arnott started selling Chinesium compressors, which you can get on Ebay, and AMK compressors, which you can get cheaper elsewhere.
Bilstein and AMK remain solid thus far, but I do not know a reputable manufacturer for the valve blocks. Fortunately if you don't run the compressor on a leaky system, moisture won't get in and the valve block will last a very long time.
P.P.S. Replace the compressor intake air hose when you replace the compressor. The molded rubber has a tendency to crack and thus let in dirty air, presumably leading to premature wear.
Bilstein and AMK remain solid thus far, but I do not know a reputable manufacturer for the valve blocks. Fortunately if you don't run the compressor on a leaky system, moisture won't get in and the valve block will last a very long time.
P.P.S. Replace the compressor intake air hose when you replace the compressor. The molded rubber has a tendency to crack and thus let in dirty air, presumably leading to premature wear.
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Joined: May 2013
Posts: 81
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From: Houston, TX
'98 E320 and '08 GL320
Yes, I had basically replaced every component with Arnott around 4 years ago. At the time they had a lifetime warranty on the air springs. Fortunately, they honored that warranty and eventually replaced all four air springs last June as they were leaking. I think the modern warranty is only for a year or two. At the time, I had also experimented with buying some air springs from a no-name company on Amazon for around $50 each. They claimed to be compatible with the GL, but when they arrived, they were noticeably smaller in diameter than the originals, so they got returned. My original MB valve block is lost in the chaos of my garage, but I have three blocks sitting on my bench right now, one super cheap no-name Amazon buy, one from Arnott, and one from an actually reviewed and "recommended" (still an off-brand), and they all are identical to one another. Probably all came from the same factory.
Anyway, when I saw that none of the air lines had actually engaged their retaining rings in the valve block, it is no surprise that the system was leaking. I can understand a compressor losing its compression due to wearing out, but am surprised that motor failed on this compressor. Tried bench testing it, and it is dead for sure.
Anyway, when I saw that none of the air lines had actually engaged their retaining rings in the valve block, it is no surprise that the system was leaking. I can understand a compressor losing its compression due to wearing out, but am surprised that motor failed on this compressor. Tried bench testing it, and it is dead for sure.
Thread Starter
Member
Joined: May 2013
Posts: 81
Likes: 8
From: Houston, TX
'98 E320 and '08 GL320
Things may have changed in the last few years, but the go-to compressor always was AMK. Nobody reported good results with any other make.
You need to clear the error codes before the suspension will resume normal operation. It will helpfully avoid running the compressor when it thinks the system is leaking. The codes might self-clear with drive cycles, but it is much quicker and safer to do it manually.
If you have the means and inclination, a bidirectional scan tool is highly recommended. For example, accessing the Airmatic module, you'd be able to raise and lower individual corners on the vehicle. This might have saved you some pain.
My general impression that Autel is on the leading edge of third party scan tools - my MP808 seems quite solid - but there may be others.
No-name parts are hit-or-miss. I installed a valve block that was non functional out of the box. TPMS lasted from one to five years. But my no-name thermostat has held up faithfully for 50k miles now. To be safe, I now only install the best, near-OEM, parts - but still that is not a guarantee I won't be found crying in the garage.
You need to clear the error codes before the suspension will resume normal operation. It will helpfully avoid running the compressor when it thinks the system is leaking. The codes might self-clear with drive cycles, but it is much quicker and safer to do it manually.
If you have the means and inclination, a bidirectional scan tool is highly recommended. For example, accessing the Airmatic module, you'd be able to raise and lower individual corners on the vehicle. This might have saved you some pain.
My general impression that Autel is on the leading edge of third party scan tools - my MP808 seems quite solid - but there may be others.
No-name parts are hit-or-miss. I installed a valve block that was non functional out of the box. TPMS lasted from one to five years. But my no-name thermostat has held up faithfully for 50k miles now. To be safe, I now only install the best, near-OEM, parts - but still that is not a guarantee I won't be found crying in the garage.
