"Something Is Moving" Sound after Engine turn Off

[Drooby]

I am recently noticing a sound like "something is moving" or "mechanically pumping" ........... anyway a sound like that but NOT Clinging or rattling
Its Coming from inside the hood and I only notice it AFTER I turn the car OFF.

It continues for about 5-10 seconds and thats it .
Anyone have any idea what this is ..?

thanks

[Patrick]

It's the air vents closing automatically -nothing to worry about, just another special feature on BMW's. As far as I know it's to keep dust and pollution from "contaminating" the interior.

[Paul in NZ]

and whirring goes on for ages..........

[winfred]

on a car with a bosch ac compressor sometimes the compressor will run backwards till the pressures in the systen equwalize after the engine is shut off, it's very common

[Drooby]

Thanks guys - I was a bit worried (only had this car for a couple of months so I am still noticing stuff like this and getting worried )

Upgraded (my last beamer was a 1974-2002S ) - what a difference

[DueyT]

Drooby, between position 0 and 1 on the HVAC controls, there are ventilation doors that open progressively (electric actuators) - hence the "curved wedge" image above the knob - 0 fully closed, from 1 onwards to 4, the doors are full open. Like Patrick notes, upon shutdown, these door actuators cycle closed with a buzzing, humming sound until fully closed. My car takes about 15-20 seconds before it stops.

Cheers,
Duey

[Warren N.CA]

Thanks guys - I was a bit worried (only had this car for a couple of months so I am still noticing stuff like this and getting worried )

Upgraded (my last beamer was a 1974-2002S ) - what a difference

[Joestancampiano]

How can the compressor run backwards after the engine shuts down? Is this an area 51 thing?

[Bill R.]

then the discharge pressure side is much higher than the suction side and the high discharge pressure will push the piston down on whatever cylinder is halfway up.. it won't usually cycle too many times before the pressures equalize.

How can the compressor run backwards after the engine shuts down? Is this an area 51 thing?

[winfred]

my 535 does it for about 10 seconds but we had a 88 735il shop car a few years ago that would do it for a minute or more, however that car had the hands down coldest ac i've ever felt in a euro car. it's hard to describe the noise, ticka-ticka-ticka-ticka- one to two ticka-'s a second depending how worn the valves are