Airmatic suspension - confirm diagnosis of internal leak in valve block please
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Joined: Jun 2021
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W221 S550
Airmatic suspension - confirm diagnosis of internal leak in valve block please
Hello,
can I ask you to confirm my diagnosis of the sagging air suspension in my new-to-me S500 (S550) 4matic? The car starts dropping (front only) after standing for a few hours, until it is very low at the front after 24 hours. When being started, it shows no error message on the dashboard and rises to the correct height within 15 seconds. It drives faultlessly (it is a Mercedes after all).
In my private workshop, I run the car and sprayed the pressure lines to the front shocks and the connectors at the valve block with leak detection spray (soapy water in a can) with no results - no bubbling nowhere.
I then rose to car to the high suspension setting, turned it off and unscrewed the pressure line from the compressor to the valve block at the compressor, then submerged the pressure line in a glass jar filled with water.
Very slowly, and in intervals of 20 to 25 seconds, single bubbles formed at the end of the pressure line. I have a video - it is as exciting as watching grass grow:
https://www.dropbox.com/s/mhow5cowyi...bbles.mp4?dl=0
This makes me believe that there is an internal leak in the valve block, allowing pressurised air from the shocks (by coincidence, both front shocks) to slowly leak towards the compressor where it is released into the atmosphere.
I can also hear the car moving around pressure every few minutes after being shut off. The car seems to re-pressurise the front shocks from the pressure reservoir, until the reservoir is empty and the car starts sagging.
Well, am I right? A new valve block is less expensive than two new front shocks...
Arne
can I ask you to confirm my diagnosis of the sagging air suspension in my new-to-me S500 (S550) 4matic? The car starts dropping (front only) after standing for a few hours, until it is very low at the front after 24 hours. When being started, it shows no error message on the dashboard and rises to the correct height within 15 seconds. It drives faultlessly (it is a Mercedes after all).
In my private workshop, I run the car and sprayed the pressure lines to the front shocks and the connectors at the valve block with leak detection spray (soapy water in a can) with no results - no bubbling nowhere.
I then rose to car to the high suspension setting, turned it off and unscrewed the pressure line from the compressor to the valve block at the compressor, then submerged the pressure line in a glass jar filled with water.
Very slowly, and in intervals of 20 to 25 seconds, single bubbles formed at the end of the pressure line. I have a video - it is as exciting as watching grass grow:
https://www.dropbox.com/s/mhow5cowyi...bbles.mp4?dl=0
This makes me believe that there is an internal leak in the valve block, allowing pressurised air from the shocks (by coincidence, both front shocks) to slowly leak towards the compressor where it is released into the atmosphere.
I can also hear the car moving around pressure every few minutes after being shut off. The car seems to re-pressurise the front shocks from the pressure reservoir, until the reservoir is empty and the car starts sagging.
Well, am I right? A new valve block is less expensive than two new front shocks...
Arne
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Joined: Jun 2020
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'11 E350, '11 E550, '98 M3, '95 E320
I'll add, usually there's a valve on the output of the airmatic compressor, which either allows pressurized air into the valve body and system OR it vents, allowing lowering of suspension. So it [valve in compressor] would also have to be defective for the system to leak out.
More likely one or both struts are leaking, assuming you've checked the lines and connections for leaks.
More likely one or both struts are leaking, assuming you've checked the lines and connections for leaks.
MBWorld Fanatic!
Joined: Oct 2010
Posts: 5,141
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
The obvious leak is seen by just looking at the car. Air bubbles coming out at phase “like looking at grass growing” tells me it is not a valve leak issue especially as there should be two valves leaking at the same time.
It most likely is leak in air spring that was already also mentioned.
Super Member
Joined: Feb 2009
Posts: 717
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From: Brooklyn, NY
2007 S550 4Matic 2013 S550 Base
Scanner will not know if valve is leaking. It only knows if valve is in open or closed position or if the circuit is broken (=solenoid coil bad or bad connection).
The obvious leak is seen by just looking at the car. Air bubbles coming out at please “like looking at grass growing” tells me it is not a valve leak issue especially as there should be two valves leaking at the same time.
It most likely is leak in air spring that was already also mentioned.
The obvious leak is seen by just looking at the car. Air bubbles coming out at please “like looking at grass growing” tells me it is not a valve leak issue especially as there should be two valves leaking at the same time.
It most likely is leak in air spring that was already also mentioned.
