GL Suspension whoas
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
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From: Emmett, ID, USA
2007 GL450
Welp. No help. I now have a spare, used, working valve block.
I figured out the compressor can be causing this leakage. It has valves inside it. The compressor may also be relying on the piston seal to maintain the central pressure.
Replacement compressor (I ordered a cheapo as well as a replacement from Arnott) should be here today.
I figured out the compressor can be causing this leakage. It has valves inside it. The compressor may also be relying on the piston seal to maintain the central pressure.
Replacement compressor (I ordered a cheapo as well as a replacement from Arnott) should be here today.
Thread Starter
Super Member
Joined: Nov 2018
Posts: 604
Likes: 16
From: Atlanta, GA
2001 S500 (W220) / 2007 GL450 (X164)
Welp. No help. I now have a spare, used, working valve block.
I figured out the compressor can be causing this leakage. It has valves inside it. The compressor may also be relying on the piston seal to maintain the central pressure.
Replacement compressor (I ordered a cheapo as well as a replacement from Arnott) should be here today.
I figured out the compressor can be causing this leakage. It has valves inside it. The compressor may also be relying on the piston seal to maintain the central pressure.
Replacement compressor (I ordered a cheapo as well as a replacement from Arnott) should be here today.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
Likes: 628
From: Emmett, ID, USA
2007 GL450
Update: The Chinesium compressor simply does not work in the system. I have heard that if the computer sees anomalous information coming from, for example, the pressure sensors, it just shuts the whole thing down. That is what my system does; the air bags remain inflated, but the computer does not order the self leveling upon opening the door. I'll check the electrical connections and then put in the Arnott pump if I can find no other cause.
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NGL450 w/EORP, S550
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
Likes: 628
From: Emmett, ID, USA
2007 GL450
Update: The Chinesium compressor simply does not work in the system. I have heard that if the computer sees anomalous information coming from, for example, the pressure sensors, it just shuts the whole thing down. That is what my system does; the air bags remain inflated, but the computer does not order the self leveling upon opening the door. I'll check the electrical connections and then put in the Arnott pump if I can find no other cause.
Ended up getting an Autel. MP808. It's really sad you have to buy all this functionality for every car ever made in order to get the interactive capability, but it is what it is. It already paid for itself troubleshooting the system; I put the Arnott pump on the Chinesium valve block to figure out the fault was truly in the valve block. Recommended.
Thread Starter
Super Member
Joined: Nov 2018
Posts: 604
Likes: 16
From: Atlanta, GA
2001 S500 (W220) / 2007 GL450 (X164)
I'm so frustrated right now! Took the car to a shop for a second opinion and they say that they don't see the codes (5503 & 5508).
Then they tell me that because I have an aftermarket radio they are worried about the wiring and the air bus and the cascading effect of
problems blah blah blah.
Long sorry short they said they aren't able to diagnose it which makes me think that they don't have the proper scanner to trigger testing of things like the compressor and stuff.
At this point I feel like I might just throw the 2 front struts on and if that doesn't work throw another compressor on.
Then they tell me that because I have an aftermarket radio they are worried about the wiring and the air bus and the cascading effect of
problems blah blah blah.
Long sorry short they said they aren't able to diagnose it which makes me think that they don't have the proper scanner to trigger testing of things like the compressor and stuff.
At this point I feel like I might just throw the 2 front struts on and if that doesn't work throw another compressor on.
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MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
Likes: 628
From: Emmett, ID, USA
2007 GL450
I'm so frustrated right now! Took the car to a shop for a second opinion and they say that they don't see the codes (5503 & 5508).
Then they tell me that because I have an aftermarket radio they are worried about the wiring and the air bus and the cascading effect of
problems blah blah blah.
Long sorry short they said they aren't able to diagnose it which makes me think that they don't have the proper scanner to trigger testing of things like the compressor and stuff.
At this point I feel like I might just throw the 2 front struts on and if that doesn't work throw another compressor on.
Then they tell me that because I have an aftermarket radio they are worried about the wiring and the air bus and the cascading effect of
problems blah blah blah.
Long sorry short they said they aren't able to diagnose it which makes me think that they don't have the proper scanner to trigger testing of things like the compressor and stuff.
At this point I feel like I might just throw the 2 front struts on and if that doesn't work throw another compressor on.
The shop may not have MB-specific scan tools (e.g. MBII, Autel), so they only know generic OBD, which probably does not include those Airmatic codes.
Without a two-way system, e.g. Autel or DAS, you are pretty much flying blind. You have to be able to actuate valves on the block in order to determine much of anything. Otherwise the best you can do is read the pressure inside the valve block chamber, which is small and will pretty much always sag down on its own, making you think you have a leaky system.
The reservoir fill time error is most likely due to the pump wearing out. It simply has developed too much internal leakage. There could be other leaks, such as between the pump and the valve block, and between the valve block and the reservoir - and on the reservoir itself - but these are much less likely barring physical damage, and can mostly be checked externally pretty easily.
So in short, if you have the fill time error, you probably have a worn out pump. I would do the pump first and then the struts if that doesn't help. And the struts only have a problem if they sag overnight. Or you do the soapy wooder trick and find stoner spit on the air bags.
Thread Starter
Super Member
Joined: Nov 2018
Posts: 604
Likes: 16
From: Atlanta, GA
2001 S500 (W220) / 2007 GL450 (X164)
Yes, it's frustrating, especially without the tools to give you insight into and control over the systems. You're stumbling in the dark with your hands tied behind your back.
The shop may not have MB-specific scan tools (e.g. MBII, Autel), so they only know generic OBD, which probably does not include those Airmatic codes.
Without a two-way system, e.g. Autel or DAS, you are pretty much flying blind. You have to be able to actuate valves on the block in order to determine much of anything. Otherwise the best you can do is read the pressure inside the valve block chamber, which is small and will pretty much always sag down on its own, making you think you have a leaky system.
The reservoir fill time error is most likely due to the pump wearing out. It simply has developed too much internal leakage. There could be other leaks, such as between the pump and the valve block, and between the valve block and the reservoir - and on the reservoir itself - but these are much less likely barring physical damage, and can mostly be checked externally pretty easily.
So in short, if you have the fill time error, you probably have a worn out pump. I would do the pump first and then the struts if that doesn't help. And the struts only have a problem if they sag overnight. Or you do the soapy wooder trick and find stoner spit on the air bags.
The shop may not have MB-specific scan tools (e.g. MBII, Autel), so they only know generic OBD, which probably does not include those Airmatic codes.
Without a two-way system, e.g. Autel or DAS, you are pretty much flying blind. You have to be able to actuate valves on the block in order to determine much of anything. Otherwise the best you can do is read the pressure inside the valve block chamber, which is small and will pretty much always sag down on its own, making you think you have a leaky system.
The reservoir fill time error is most likely due to the pump wearing out. It simply has developed too much internal leakage. There could be other leaks, such as between the pump and the valve block, and between the valve block and the reservoir - and on the reservoir itself - but these are much less likely barring physical damage, and can mostly be checked externally pretty easily.
So in short, if you have the fill time error, you probably have a worn out pump. I would do the pump first and then the struts if that doesn't help. And the struts only have a problem if they sag overnight. Or you do the soapy wooder trick and find stoner spit on the air bags.
I guess I could spray soapy water on the components to look for a leak.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
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From: Emmett, ID, USA
2007 GL450
Remember the valve block's normal state is all valves closed. You only read a location's pressure by opening the valve to that location and none others. The problem with the MBII is it tells you the pressure sensor reading but doesn't allow you to activate any valves - meaning all you can read is the pressure inside the valve block chamber.
To fill the reservoir, the system turns on the pump and opens the valves to the pump and to the reservoir. So you can see it's a pretty simple system after all, without very many places to go wrong.
I chased my tail because I couldn't believe the Arnott pump had failed after 20k miles. I get the feeling you are similarly in disbelief. It can happen; it's a pretty tough situation the pump is put in.
One problem with the MBII is you do not have the ability to reset the pump timer. Autel will let you do that. I wish I had with the Arnott pump, because I could have figured out whether the pump is running excessively.
Spray some soapy wooder and order yourself a replacement pump. I wish I could tell you the right kind, but I'm as stumped as everyone else on what are actually good parts for this suspension. Figure out who the OEM supplier is? My original lasted more than 150k miles; I replaced it purely because I was assuming it was on its last legs and Arnott would be better.
Thread Starter
Super Member
Joined: Nov 2018
Posts: 604
Likes: 16
From: Atlanta, GA
2001 S500 (W220) / 2007 GL450 (X164)
Won't take but a few seconds. Everyone should own a wash bottle, dish detergent and water.
Remember the valve block's normal state is all valves closed. You only read a location's pressure by opening the valve to that location and none others. The problem with the MBII is it tells you the pressure sensor reading but doesn't allow you to activate any valves - meaning all you can read is the pressure inside the valve block chamber.
To fill the reservoir, the system turns on the pump and opens the valves to the pump and to the reservoir. So you can see it's a pretty simple system after all, without very many places to go wrong.
I chased my tail because I couldn't believe the Arnott pump had failed after 20k miles. I get the feeling you are similarly in disbelief. It can happen; it's a pretty tough situation the pump is put in.
One problem with the MBII is you do not have the ability to reset the pump timer. Autel will let you do that. I wish I had with the Arnott pump, because I could have figured out whether the pump is running excessively.
Spray some soapy wooder and order yourself a replacement pump. I wish I could tell you the right kind, but I'm as stumped as everyone else on what are actually good parts for this suspension. Figure out who the OEM supplier is? My original lasted more than 150k miles; I replaced it purely because I was assuming it was on its last legs and Arnott would be better.
Remember the valve block's normal state is all valves closed. You only read a location's pressure by opening the valve to that location and none others. The problem with the MBII is it tells you the pressure sensor reading but doesn't allow you to activate any valves - meaning all you can read is the pressure inside the valve block chamber.
To fill the reservoir, the system turns on the pump and opens the valves to the pump and to the reservoir. So you can see it's a pretty simple system after all, without very many places to go wrong.
I chased my tail because I couldn't believe the Arnott pump had failed after 20k miles. I get the feeling you are similarly in disbelief. It can happen; it's a pretty tough situation the pump is put in.
One problem with the MBII is you do not have the ability to reset the pump timer. Autel will let you do that. I wish I had with the Arnott pump, because I could have figured out whether the pump is running excessively.
Spray some soapy wooder and order yourself a replacement pump. I wish I could tell you the right kind, but I'm as stumped as everyone else on what are actually good parts for this suspension. Figure out who the OEM supplier is? My original lasted more than 150k miles; I replaced it purely because I was assuming it was on its last legs and Arnott would be better.
I honestly didn't know that the MB ii could do that much. I had one shop tell me that one of my struts were leaking but that was so odd because it never sags at all.
I will check for leaks and look at changing the pump first. Hopefully that will fix the issue.
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Joined: Nov 2019
Posts: 648
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From: Yeast Coast, Canada
GL550 X164
The bags' OE supplier is Ate. I would not be surprised if they make all the components for the Airmatic system.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
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From: Emmett, ID, USA
2007 GL450
There is a similar AMK sticker on what is supposedly a Bilstein compressor:
This would not be a huge surprise. Bilstein does not necessarily make everything in-house. They might buy parts and put their brand on them.
A fellow selling an AMK pump parked it on top of a MB box, saying it is genuine:
So this seems to be lining up to: AMK is the OEM supplier.
The P-2594 Arnott compressor (which Arnott says, via Amazon, fits X164) has an AMK sticker on the motor body:
The older (but not by much; see the test date of 2/2020) Arnott 3214 pump (which is what Arnott's web site shows as the part for X164 and W164) does not show AMK:
While this P-2858 (for X166) from Arnott (though not on their web site) does appear to be AMK:
Below about $350 there are no AMK compressors on Ebay. After that it's Chinesium all the way down.
Last edited by eric_in_sd; Mar 20, 2021 at 12:39 PM.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
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From: Emmett, ID, USA
2007 GL450
There are also "Cardone" compressors; they are AMK.
I'm real curious who makes the non AMK Arnott compressors. I wonder if they are Chinesium. Considering I got 17k miles out of mine, I wouldn't be surprised.
Air compressors wear out pretty fast. They're just like a compression engine; imagine running your motor without oil, just aluminum pistons slapping around inside aluminum cylinders, and you can imagine how expensive a compressor would be if it were built to last for, say, a thousand hours. You'd need a piston with rings, a chrome steel cylinder sleeve, and an oil lubrication system for the piston rings. 1/8 of the GL's motor, in other words.
Overheating the compressor is terrible for it, too. The piston and cylinder wear out exponentially faster the hotter they get. I have a little tire inflator compressor; I mounted little 12V fans on the heat sinks on the head to help cool when pumping. Which is another reason to stay on top of leaking bags - they bring down the compressor, and the dryer inside the pump gets overloaded, pushing moisture into the valve block - it's a mess!
If your pump fails, don't throw it out. That's a real nice 12V DC motor in there. The pump head is scrap but the motor is probably still fine.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
Likes: 628
From: Emmett, ID, USA
2007 GL450
Sad!
I bought an open box AMK on Ebay for ~$350. When I get settled in at the new house I'll swap it for the Chinesium model. Or maybe wait for the latter to fail - dunno.
Properly situated, and not abused, the German or American made compressors will last a long time.
Note the venturi vacuum oil suction will put a lot of wear and tear on your compressor. They simply are not meant to have that long a life. Good shop compressors have rings on the pistons, an iron sleeve in the cylinder, and an oil bath system, and will last nearly forever. Any mass market compressor simply won't last long. It's purely a function of hours of use - cycles of the piston - with a temperature multiplier.
I should have known there was something to it - I was able to sell my used 150K mile air pump for ~$50. Had I known I had installed an air pump that would only last 17K miles, I would have left it in there.
Did y'all consider that the M273 motor has an 11:1 compression ratio, meaning it puts out 10 bar? If you put a jake brake on it, you could inflate the air suspension, kinda. The diesel motor has enough compression to do it, for sure.
