On the driver side under the rear bumper there is a little part that has a rubber cover over it. Every time I turn my van off I hear a kind of loud buzzing noise. I like to think I know a little about cars, but I have no idea what this part is, or what it does, or if I need to be worried about the noise. Any help would be great

 

Do you have the optional load leveling suspension ? If you do it is the pump for the air shocks.

 

+1 Gregdd

When you first start the van is usually when you will hear the compressor running or if it is already running and you load some heavy cargo in the back. Noisy kids will however drown it out so you won't even know it is there. A simple way to tell if you have self leveling, look from under the back bumper at the rear shocks and if there is what looks like a thin wire plugged into the middle of them you have it.

It will occasionally run after you take the key out, but I'm not sure I would describe it as a buzzing noise. How long have you had this van?

 

One thing about the load leveling that I don't like. It will run when the van is turned off. Once when parked off road on an rutted out surface. The pump would continuously run and then release air over and over until I moved the van. Makes me think if you had a leak it might run until the pump died.

 

That doesn't sound right. Probably kill the battery before the pump, which could then leave you stranded somewhere. I've heard mine running right after taking the key out, but once it finishes that cycle it doesn't run again until you put the key back in.