I think Frank C. talks about boiling for several hours. Heat up, let crud boil, agaitate with nuts and bolts in the tank, let keep boiling. And just because it doesn't have a hint of gas smell doesn't mean it can't explode. I'm guessing this could go down to local radiator repair shop and get boiled out for 25-50 bucks and then you won't need to worry about a large kaboom.