Boiler crack in cast iron block

dtopp45

Hi I have a question about my boiler. Pressure was low and found a leak on the block which the tech confirmed. Not a big leak and doesn't leak on to the ground all the time. Heat still going and getting estimates to replace/hoping it keeps going until then. The tech turned the auto fill valve off to keep the pressure down to keep it alive longer (I think??). However I'm not sure there's a low water cut off. How would I know? Is this asking for it to run dry?? Thoughts?