hey
easy ways to check if your hg is gone... do a compression check.. let us know your numbers they should be 142 or above.. make sure they are even and don't differ by more than 14psi between cylinders
if you compression check comes up good you can next try a block check and see if there are exhaust gasses in the water
other than those tests there are just the usual tell tale signs, water bubbling out the overflow, overheating or spiking of the temp gauge
i can't think of any others off the top of my head right now
let us know how you get on
