Over on Warhammer Empire I came across the topic Is steam tank totally unfair?.
I think that we've been playing it wrong. The way I thought it worked was choose a number of steam points you want to use, roll a dice, and if the total wasn't more than your wounds then the original number plus the D6 was the number of steam points you have available to use to move/charge etc.
The way that it does work is you choose a number of steam points you want to use. This will be the number of steam points available to you if the overload doesn't occur.
The rolling of the D6 is just to see if an overload occurs. Roll the dice and add the number to the number of steam points. If the total is more than your wounds then you can't move or shoot this turn and you take one wound. The D6 doesn't give you steam points that you can use.
That steam tank is not so scarey after all.