2005 E320 CDI: Something's Running...
 

occasionally when I approach the Car, to open the door, trunk, or get in, I hear a quiet, efficient whirring sound for a couple seconds, like a small electric motor is running. What is this? First I thought of the Airmatic suspension, but I did not think the Diesels had this.
I just completed putting almost 1900 miles on Her, round trip to Bloomington, ID, including side trips to Indianapolis and West Baden Springs (worth seeing, by the way). Best tank was 39.74 MPG. Perfect performance, could not ask for better. All faces are "smiley" so far.

SBC brake pump.

And...don't do any brake service w/o first disconnecting that system. Will activate whenever a door is openned or the key gets close to the car on some models.

SBC was only around in 05 & 06. The system was a weak design that was given an 10 yr extended warranty by MB and was done away with in 07.

Ok, Thanks, both good and bad to know, I guess.
At the 110,000 mile point, I am on the "wallet" warranty.