Sounds like the notorious Lower Intake Manifold gasket if this is a 3.4L V6.
If it is the V6, use a flashlight to look behind and below the power steering pump which is located at the top pulley in the middle. If you see anti-freeze back in that area, it's likely to be the lower intake manifold gasket that's leaking. The early 3.4 V6's had this problem before a revised gasket was introduced to correct the problem.
The other things to look for on that side of the engine are leaks from any of the coolant hoses going to or from the radiator to the engine or the bottle and be sure to check for signs of a leak from the bottle cap and overflow attached to the bottle neck. Again, assuming it's a V6. Don't know about the 4 cyl.