My husband and I bought our G6 in Feb 2009 with 22k miles on it. Almost immediately we heard gurgling from the engine, on the driver side, close to the firewall. The gurgling was only heard when the engine was still cold and upon acceleration. After closer inspection, we realized the antifreeze reservoir was extremely low. We filled it up and didn't hear the gurgling until about 6 months later. We checked under the hood and, sure enough, the reservoir was empty again. If you know anything about cars, finding a slow anti-freeze leak can be like finding a needle in a haystack. So, we decided that as long as the leak is extremely slow that we would just top off the car when ever the gurgling started back.

In the first week of October of 2011, I topped of the reservoir. Then on November 29th 2011, the gurgling came back. and the reservoir was empty again. We have an appointment set up with our dealer on December 8th. The problem might be fixed under the powertrain warranty. We've done a little research and it looks like it might be leak around a gasket on the head. Hopefully that's all it is. I will update this as soon as possible.