When I start my van it makes a loud high pitch whistle sound

I just hade a belt put on before Christmas. My son said it is more of a squealing not a whistle. It is getting worse that's all I know. It is coming from the right side of the engine. Thanks for responding.

Take the belt off to see if it still makes the noise, if not then the pulleys, tensioner needs to be investigated or the belt is getting wet.

okay. Thanks

Let me know what you find.