I have an ML500 W164 - 06 (never had one before and not had long) and I started to try some of the features. The airmatic system seems to work fine, it goes up and down evenly but the pump makes quite a pronounced buzzing noise when its operating. It runs for approximately 2 minutes while it is adjusting the ride height to HIGH then switches off. It then lowers itself (on command)nicely without making a noise. Is this normal? I would be grateful for feedback from folks who have experience of this system.
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