engine whistle - 2002 wrangler

I have whistling type sound (like a tea kettle) when I turn off the engine. Belts all check out fine. Any ideas?

Perhaps radiator?

Common, it is the radiator. There is a plastic top to the metal radiator, they leak and are known to go bad. It happens to us all, my 04 w/ 12,000 miles is doing it too...

Thanks. I'll try a new radiator cap and see if that solves my annoying whistle.