I've got a 2015 S550 that I absolutely love, but over the past week I've started noticing this faint hissing sound coming from the front driver side whenever I park the car and step out, almost like air slowly escaping from somewhere. At first I thought I was just imagining things, but I've confirmed it a few times now and I'm pretty sure it's coming from the air suspension strut on that corner. The car still sits level and doesn't seem to be dropping overnight, but I know these Airmatic systems are known for developing slow leaks in the struts or the air lines over time, and that hissing sound is usually the first warning sign that something isn't sealing properly anymore. I'm honestly dreading this because I've heard horror stories about the cost of replacing these air struts, and the dealership will probably quote me something astronomical for a job that involves dropping the entire front subframe just to access everything. I've been doing some research online and it seems like there are some independent shops that can rebuild the existing struts with new seals and o-rings for a fraction of the cost of buying brand new units, which sounds like a much more sensible option if I can find someone who actually knows what they're doing. I live in MBZ City and work nearby, so I've been looking for a Genuine Mercedes repair center in MBZ City that has experience with Airmatic systems and can properly diagnose whether it's actually the strut itself or just a leaking fitting or airline that needs tightening. I really don't want to wait until the car drops to the bump stops and leaves me stranded, but I also don't want to rush into an expensive repair if it turns out to be something simple. Has anyone here dealt with Airmatic hissing issues on their S-Class and found a shop that can rebuild the struts rather than just replacing them at full price? I'd be so grateful for any advice or recommendations before I start spending money on this thing.