There has been a lot written about air in the cooling system, so try the main search function to see what all you might find.
Another approach is to find an incline nearby, when the car is cool drive there. Then with the front of the car on the high side of the incline open the overflow tank (why you should start this with the car cool) and let the system burp. Again, try the search.
The main search is the fourth item in the row beginning with "Home" it searches the entire forum. The search under the club logo will only search the topic you are currently on.
I used "cooling burp" with no quotes, and got a short list of hits - easy to read through.
Good luck.