S-Class (W221) 2007-2013: S 320 CDI, S 350, S 450, S 500, S 550, S 420 CDI, S 600

One corner collapses 30 minutes after car turned off, strut replaced but didn’t work

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Old 08-16-2019, 07:03 AM
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2011 S550 4Matic
One corner collapses 30 minutes after car turned off, strut replaced but didn’t work

My front left strut collapses completely every time I turn the car off. It’s a slow deflate that takes around 15-30 minutes and happens every time I park. I replaced the strut but the behavior is the same.

where should I look next? Air lines? Valve body?

my concern is that I thought these struts had a residual pressure relief valve at the top that stopped it from leaking if the incoming pressure dropped. If this is true, then a leaking strut is just that...
Old 08-19-2019, 01:52 PM
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2011 S550 4Matic
A bit more detail on the car's behavior:

I ran the car for about 5 minutes and it doesn't seem to be leveling itself properly. The level sensors report -1 inch at the front left and +1.6 inches at the front right. The level sensors appear fine and seem to be reporting the true height at each wheel. I suspect the level control unit (valve block) but I'd expect an error code if the solenoids were failing/leaking.

One other odd thing is that the pressure sensor only reported 1.24 bar after the car had been running for a few minutes, this seems oddly low. I thought the struts held 5-10 bar.

Any advice would be greatly appreciated! I'm dangerously close to taking it to the dealer...
Old 08-25-2019, 09:13 AM
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[ SOLVED ]

I replaced the valve body and at the same time fixed a small crack that had formed where one of the lines entered the fitting at the valve body. With these two repairs completed, the air suspension functions normally.

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