I noticed last winter that after cold start my engine would whistle for a few seconds and then after it got slightly warm it would stop.
This year it seems to be getting worse, it's not even that cold and it pretty much only stops when the engine is at operating temp (so for quite a few minutes of driving), it's also way louder/annoying/embarassing.
It changes frequency when you rev and it doesn't happen during the summer so I'm thinking something to do with pulleys, belts, alternator, waterpump ??
It's an S52B32.