Air bag is for accidents. Air spring pretty sure you mean.

Most often deflating spring is from a leak in the spring itself. Occasionally it's in a fitting somewhere but with just one side won't be at the compressor.

You can sometimes confirm with soapy water like a tire.

Young age doesn't mean it can't leak. Follow the symptoms.

We had the same year/model and had to replace both air springs. I was surprised how fast they failed on the e seventy vs. the e fifty three.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)