[CruisinG6]

A sloshing sound could really be air bubbles moving through the coolant, although its unlikely... how does the coolant look?

Just sounds odd to me you can even hear the trans fluid.

 

[CruisinG6]

I hope it is not the coolant as I am having a leak from the right side of the car (pulley area) . I figured it was my water pump going out and weeping. You can really only here it when you first start the car that's why I figured it was the tranny fluid in the torque convertor. My car is an 07 G6 V-6 and has 90,000 on it as of now.

All the more reason I think its your coolant. When the car is cold the coolant has settled and air has taken up all the of the high spots in the motor and radiator. What you're hearing is all the air bubbles being forced through the heater core behind the dash.

 

[CruisinG6]

I'd recommend keeping up on your coolant level until you get that leak sorted out. Don't want to loose your heat or damage the engine.