Coolant level dropping without a leak

I'm looking for troubleshooting advise in chasing down the cause of this. Also, any repair suggestions would be greatly appreciated on my 2008 Cobalt with a 2.2 l engine with 80000 miles on it.

Tia

You could try replacing the thermostat. Thats what I did. I mean it didnt work but it might for you...

Depending on how much coolant you are losing, it can only be going one of two places. Either leaking outside or inside. Here's what I would do. Buy or borrow a coolant system pressure tester, and pump the system up to 15 pounds. Let it set for a few minutes, and look for coolant under the vehicle and inside under the dash. If no coolant, pull the spark plugs and turn over the engine. Also check the oil. If the pressure tester drops quickly, you have a major leak and should be easy to find. If it doesn't drop at all, let the motor run till hot and test again.

Could there be air in the system? Was it flushed recently?