380SL Humming noise
 

Got a 85 380SL a few weeks ago and it has a loud humming noise coming from the right rear as soon as the engine is started. The noise is there regardless if the vehicle is moving or not. I think the problem might be part of the fuel delivery system. Anyone had this problem before?

Sounds like you've got a fuel pump that's about to go. There's some tests in the service manual that you can do to check the output volume and pressure. Probably a more telling test is how much current it's drawing.

My 380 SL did the samething. I went under the car with it running and used a stethascope (sp) to listen and the noise was definitely the fuel pump. I was told by many that it might run indefinitely like that but also it might just quit and leave me stranded. The common idea from most was that if it makes that hum something is going wrong. I decided to go ahead and change mine which is not very difficult. Humming noise went away and all has been fine since.

In my years of automotive experience I have found that generally most cars hum because they don't know the words. At least that is what I think, but I could be wrong.

This may be a long shot but I have a hum (slightly fainter than what you describe) which seems to be coming from the rear but I know that it is actually caused by the A/C and air circulation system. When I turn off the system, it stops.