How do I know if I've got a cracked block or not?

 

if its in the car look for anitfrezze driping and oil dripping . If its out of the car take it to a machine shop and they have a process that will show any cracks.but dont mistake it for a blow head gasket or a leaky intake gasket.

 

Funina pretty much covered it but whats makin you think you have a crack somewhere? how many miles are on the motor?