Could someone please explain to me or direct me to some material explaining how the AST works in the FD and its interaction with the cooling and radiator?

 

it helps clear the air bubbles in the radiator

 

It is supposed to help eliminate air from the cooling system. In my 10+ years experience with these cars, it does nothing but take up space in the engine bay and serve as yet another failure point. I recommend eliminating it on all my customer's cars. The only downside is it takes longer to burp the cooling system of air after a flush but is no problem if you know how to do it properly.

 

+1, mines eliminated.

 

we just had the same exact thread last week...

you might want to try searching.