ASZ Engine: Whistling Noise After Shut Off

Hello.
'I almost always hear a high-pitched whistling sound, twice in a row, coming from the engine compartment about a minute after I turn off the engine. The whistling sound gets progressively higher in pitch over the 4 seconds it lasts, and it starts quite quietly. There's a pause of about 2 seconds between the two whistling sounds, and both sounds are identical. I haven't been able to pinpoint the source of the noise after three attempts. Where could this noise be coming from? Could it indicate a leak in a hose, from which pressure is escaping when the car is stationary?'

cu moby

When the car is off, there's only vacuum left... so it could be a vacuum valve that's switching. I only hear it when the parking brake lever is released, but that sound stops about 10 seconds after the engine is turned off.

Hello,
Was the air conditioning on before you parked?
haithamina

Hello,
Was the air conditioning on before you parked?
haithamina

Hello, I'm just going to take them off now... it's not quite as warm anymore.

cu moby