>blowing out is getting combustion pressure into the cooling system 
>and popping 'em off.  been there, done that in a rabbit diesel.
>
>head gaskets would be the likely culprit. sorry.
>
thought about this too, pressure cap should blow off pressure at 15psi or 
so, anyone verified a pressure cap malfunction. You should blow your coolant 
into the overflow tank, along with gasses.... anyone know if this tank 
breathes? It should!  tim s