Originally posted by black 1994 c280
I have the same sound on my 94 C280. I was told that it was the vacuum pump
it IS the vacuum pump which is used for the central locking, airconditioning system (operation of valves in the heater housing) and possible multi contour seats...
A humming sound every 2 minutes is too often and not that normal...but as long as the sound only continous for 2 seconds, I wouldn't pay too much attention to it.