how does a shop check an engine crank case or the head for cracks if the engine overheated?

 

the check more for warpage when when it overheats. They check the surfaces with a straight edge and feeler guage underneith it to make sure all the clearances are the same = straight non warped surface along the Deck and the head.

Some shops use magniflux or x-ray to check for cracks that you can't see.

 

They would most likely use dye for aluminum. Magnaflux only work for ferromagnetic materials.

 

when you overheat an engine the bottom end does not warp?? why?