Did a little troubleshooting tonight after work. I'm thinking the whistle (more like a whine) is the water pump. My radiator developed a leak a while ago, not sure when. I've put water in a couple times, it's never overheated on me, but it's definitely wet in the center bottom. I've also been noticing large puddles under her after a good drive. Anyway, I got her warmed up and turned the heat on... No warm air. So...I ordered everything but the pump for a cooling system overhaul from Amazon. I'll see if I can source a Mopar pump locally... Amazon was out and the online parts stores want a lot of money to ship. My wife has taken to calling my Jeep the "money pit"