ok i have a 2008 pontiac g6 gt 3.5L and i am wanting to know how to bleed the coolant system of air?

Starting with a cold engine, fill the radiator to the top and leave the cap off. Also fill the overflow reservoir to the "cold" line. Now start the car and let it warm up a little until the thermostat opens and allows coolant to flow into the radiator. At his point, some coolant will likely "burp" from the open radiator cap along with the trapped air. Replace the cap and allow the engine to reach operating temp. Observe the coolant level in the reservoir and add as much coolant that will bring the level up to the "hot" line. Shut the car down and allow it to cool for 30 minutes and re-check the reservoir level - it should be bacck down to the "cold" line.

Check your secondary fan relay. Look under the hood when it's starts getting over normal temperature. The second fan should be on. If it's not, you have a bad fam relay

Bad head gasket.