KCe550

Strangest thing… I unlocked my 2008 E550 while walking toward it in a parking lot today and a loud squeal came from the front of the car. I opened the hood to confirm it was indeed coming from my car and to trace the source. Might have been front left side but it was hard to tell. The squeal sounded like the sound of a loose belt on an older vehicle but no belts were visible and the engine wasn’t on. It lasted about twenty seconds and then faded away. I seem to remember also hearing the sound of compressed air being released, which I've noticed on other occasions.

I’m new to this car and Mercedes and didn’t expect that. It didn’t happen at my next stop/parking instance, but did squeal again briefly when I turned the car off in my garage.

What is this?

CaliBenzDriver

Do you have air suspensions aka AirMatic ?
The chassis height is managed by air compressor and sensors that can develop repair needs.

You can read OBDII computer faults with a handhelp scanner to confirm the health report.

KCe550

Thanks, yes my car has some kind of air suspension which was allegedly repaired about a year ago. I will try the code scanner trick per your recommendation.

KCe550

Could it be the SBC system?

Heguli

No SBC on a 2008 car, it was dropped with the face-lift in 2006.

E500 AMG Sport

The sound happened after hitting the unlock button?
Probably a bad alarm siren which also makes a sound when locking & unlocking the vehicle.
Try pressing the Panic button on the remote and see what happens.
Siren is behind the driver front wheel well liner.

nd-photo.nl

In that little box. This picture is from my W219 chassis, but should be similar/identical