I have a 2001 s40 and have started to hear a whining sound on idle coming from somewhere near the air filter box, cant quite pinpoint the exact location. Any help would be appreciated. Thanks

 

Could it be a whistling sound from the dipstick? That's a sign of a clogged PCV system.

Near the air filter box. Lets see, trans is underneath. Pump for windshield washer. Cooling fans. Relays in the fuse box.

A mechanics stethoscope helps tracking down unusual noises. A flexible hose held to your ear can be a cheap substitute.

 

Gonna try and pay more attention to the location