Sound for a few minutes after I shut off the car?

[JJeep]

Sometimes I hear a continuous sound, sort of a droning sound, when I shut off the car with the remote key. It happens randomly one in 10 times.

I haven't been able to determine how it lasts, since have to use the key again to stop it.

Is this normal?

Thanks.

 

[JJeep]

EDIT: It is a continuous hissing sound rather droning.

 

[Bricktop X PWR]

All Snake jokes aside, hissing would indicate pressure being lost.

Have you checked your coolant levels.

Probably the only pressurised thing on the car along with your tyres and A/C system.

 

[Ian Key]

Have you had AC running? It could be the AC gasses decompressing.