Hissing Sound - Underneath Car When Opening Door
 

I have the Comfort Access option and when I put my hand on the door handle and it unlocks there is always a hissing sound from underneath the car--like air being let out of a balloon. What is that ?

your chariot is awakening. specifically, i have no idea. might be the rear suspension, or the fuel pump priming. plus all of the electronic gizmos boot up when you open the door with CA.

Bump... In case someone knows now.

I have the same thing. Been trying to figure out what it is.

Snake.

Maybe a pissed off X5?

If the car has been parked and the key has not beem moved within 20 feet for 20 minutes or more, the sound you hear may be the fuel priming function. If you have a very low tank you will hear more of a hissing sound.

^ wow that actually makes sense.

<-- going to start up the lawn mower in a few mins and I recall it sounds like that when priming.

No comfort access here, and a full gas tank. My daughter opened the rear door first yesterday and we heard that loud hissing sound too. Never noticed it before.

I'm not surprised to be honest. This is my 4th BMW in the last 20 years and they've been and endless source of strange and unusual noises at strange and unusual times.

Do you have the 3rd row seat? If so it should be the rear air suspension....