Tracking Down Air Suspension Leak... Advise?
Thread Starter
Junior Member
Joined: Jan 2019
Posts: 43
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GL350
Tracking Down Air Suspension Leak... Advise?
2011 GL350
Front Left has been dropping overnight. Put my Autel 906TS on to diagnose suspension components. All components checked out within spec. Only item the scanner cannot perform a test on is the air line(s) between the control valve and each strut, leading me to believe the line is the culprit. Is there any way to test the air line? (I've done the soapy water test on both the control valve and strut air connection and no noticeable leak). Guessing the line has hair line crack(s) or chaffing somewhere along the routing by the firewall??? All though the strut tested within spec, is there any reason to believe it still may be the failure???
Thx for any input...
Front Left has been dropping overnight. Put my Autel 906TS on to diagnose suspension components. All components checked out within spec. Only item the scanner cannot perform a test on is the air line(s) between the control valve and each strut, leading me to believe the line is the culprit. Is there any way to test the air line? (I've done the soapy water test on both the control valve and strut air connection and no noticeable leak). Guessing the line has hair line crack(s) or chaffing somewhere along the routing by the firewall??? All though the strut tested within spec, is there any reason to believe it still may be the failure???
Thx for any input...
MBWorld Fanatic!
Joined: May 2015
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From: Allentown, PA
'08 GL 320 CDI
What do you mean "The strut tested within spec"?
Correct me if I'm wrong, but... how does the scanner know if the bag, specifically, is good, or not? Or, for that matter, how does it differentiate anything downstream of the valve block (as far as leaks)? Meaning, it wouldn't know if a line is leaking, the fitting at the bag or the bag itself.
Do the soapy water test on the bag. In both normal and raised positions. By far (and feel free to search for threads on this, because there are MANY), the most common culprit is the bag. Holes in the bag sometimes only present at certain "folded" positions. Good place to start testing.
Correct me if I'm wrong, but... how does the scanner know if the bag, specifically, is good, or not? Or, for that matter, how does it differentiate anything downstream of the valve block (as far as leaks)? Meaning, it wouldn't know if a line is leaking, the fitting at the bag or the bag itself.
Do the soapy water test on the bag. In both normal and raised positions. By far (and feel free to search for threads on this, because there are MANY), the most common culprit is the bag. Holes in the bag sometimes only present at certain "folded" positions. Good place to start testing.
Thread Starter
Junior Member
Joined: Jan 2019
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GL350
The Autel 906TS runs a Pneumatic Test on each individual suspension component one by one by activating compressor for a short time to bring specific component into range then holding for 30sec (+/-) to monitor any change in "bar". If the scanner determines the specific component is holding air pressure within a predetermined range, it shows component as "functioning properly". The diagnostic procedure indicates that it cannot test the air line functionality between the control valve and struts/airbags for obvious reasons.
If I misunderstood the process, then I stand corrected, but thought it was rather thorough and straight forward.
I'll perform the soapy water test on the bags to determine if any signs of leaks.
Thx for the reply.
If I misunderstood the process, then I stand corrected, but thought it was rather thorough and straight forward.
I'll perform the soapy water test on the bags to determine if any signs of leaks.
Thx for the reply.
MBWorld Fanatic!
Joined: May 2015
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From: Allentown, PA
'08 GL 320 CDI
Ok, I think I understand. However, there is no way for the computer to know if the bag, line or fitting is the culprit (should there be a leak). In essence, the line/fitting/bag are all "one thing" in the eyes of the computer. The only sensor is the level sensor... but if ANY of those three things (bag/fitting/line) had a leak, the result would be the same... the bag deflates. Play with the suspension settings and bags - while it does happen, a line leaking is definitely the more rare thing - with the bag being the most common. It's actually quite common for the bag, in early stages of demise, to have a hole that "closes up" when it's folded just right.
MBWorld Fanatic!
Joined: Jan 2010
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NGL450 w/EORP, S550
All a scan tool can do for you here is to tell you where your eyes should be looking and where to put the soapy suds...this is true even for MB Star.
as a data point, Das said my compressor tested fine even though the back cover had a broken retaining bolt.
dont trust the scanner in this case, use your eyes and ears.
as a data point, Das said my compressor tested fine even though the back cover had a broken retaining bolt.
dont trust the scanner in this case, use your eyes and ears.
