Buzzing sound inside cabin of E70 35D..

[Nyc Dito]

So once in a while after I start the vehicle I can hear a buzzing sound on the passenger side of the car, I hear it inside. BUT it does not sound like its coming FROM inside the cabin.

Today it lasted a little longer than usual so I walked outside and I couldn't really hear it. I had the radio and HVAC blower off. Came back inside, the car being on the whole time, and it was still present. I shut the engine and electrics off, and it was still going but then powered down after about 10 seconds. It sounds like a pump/motor, something that can buzz lightly, but loud enough to be heard.

I recently had to fill my DEF after I received the no start message, maybe its transferring DEF from passive to active? Yet, I've heard this sound before, even when filled with DEF.

I only hear it or notice it when starting up or after a few minutes after start up. I dont think i hear it at other times. I'm not commuting daily anymore but will try to pay attention and grab a recording the next time I drive the vehicle.

No codes, lights on dash, nothing. All maintenance up to date.

any leads, clues or suggestions would be appreciated and thanks!

[Sophisticated Redneck]

Sounds like your air pump is coming on, normal for it to do this once in awhile to auto-level the truck. To confirm, it will be loudest outside on passenger around middle of the truck as that is where the pump is located

[Nyc Dito]

Originally Posted by Sophisticated Redneck

Sounds like your air pump is coming on, normal for it to do this once in awhile to auto-level the truck. To confirm, it will be loudest outside on passenger around middle of the truck as that is where the pump is located

Thanks and yes it does sound like its coming from that area. Appreciate the reply Sophisticated Redneck ..

[Sophisticated Redneck]

Originally Posted by Nyc Dito

Thanks and yes it does sound like its coming from that area. Appreciate the reply Sophisticated Redneck ..

No problem. If you find it coming on everytime you startup, it could be indication of one of your rear air springs getting a slow leak, which is fairly common but In time it can overwork the pump so keep an eye on it and how often you hear it activate. Usually when it gets that bad you will notice your X5 sitting lower on one side before you start it up.