Low Tech test
With the system cold, make sure full of coolant (or plain ol' H2O), leave radiator/expansion cap off. Start engine, let warm a bit and gently rev it. Often a blown head gasket will build enough pressure in the cooling system to force coolant out the expansion tank.
If a fair amount of coolant comes spewing out the tank, chances are good the gasket is blown.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.