Spitting Coolant

[Bob Jacobsen <jacobsenra@hotmail.com>]

After taxing around for a while my Rotax 912S has been "spitting" some 
coolant out of the overflow bottle.  It also makes a gurguling sound.

It seems that coolant runs back into the bottle through the hose in the 
bottom and pushing some coolant out through the tiny vent hole in the cap.  
It sends out enough coolant thats its visible on the side of the airplane.  
All temps are fine, the engine runs great, there are no other coolant leaks.

Any Ideas?

Thanks

Bob Jacobsen
A131