Vehicle is making a whistling noise

So the vehicle is making a whistling noise, similar to sounding like a family of birds living under the hood.. so first off, I replaced the serpentine belt (which was fairly warn). The noise continued.. then I noticed a slight coolant (or condensation) (at this point I am not exactly sure which). so I replaced the water pump, and now it is over heating.. took it around the block and the temperature reached about 240. I have yet to change the thermostat, but it wasn't overheating before I changed the pump out.. what could have caused it? So; new Belt, new water pump...