checking for cracks in the block
 

The engine overheated. 204000 miles. The rear plastic coolant hose connection broke and coolant lost. I had the head removed and found a blown head gasket. Head gasket replaced, head surfaced .011, complete machine shop head rebuild, new valves and valve seals, head checked for cracks, none found, new head bolts. checked the block visually and with a straight edge, light sanded the block surface.
After reassembly, drove for 2 days, and overheated again. Had the coolant checked and found exhaust gas in the coolant. Will boil the coolant out after about 10 minutes of running. Also found crankcase vent valve not working.
I am resigned to taking the head off again. Is there a way to check the block for cracks without taking it to a machine shop and disassembling the block?