Cracked Head Or Block

[S47]

Whats the easiest way of checking a head and block for internal water leaks?
Recently my engine overheated after losing all the water coz of hosepipe & head gasket failure, after repairing the Hose & head gasket, the problem re-occurred, but the water must have leaked from a cracked head or Block - again dumping all the water into the engine bores, So either the head or block are cracked
I replaced the complete engine so my car is going OK but I was thinking of keeping the usable bits from the old engine.
When Looking at the old head & block there's nothing obvvious as to where [or how or why] the water is leaking - how can I tell whether its the head or Block which has the water leak problem when under engine operating conditions??
Or do I simply play safe & bin both
The engine in question is a Silvertop zetec

[dan19evans]

When the car overheated, did you have the cylinder head skimmed? If the head has warped it could cause recurring head gasket problems

[S47]

Dan
I'm certain the head wasn't warped - I checked it on a large surface table with engineers blue, after first cleaning all the crap off.
I've changed many blown head gaskets, always checking the head as above and never had a later problem, the problem is either the head or block are cracked as I stated previously, so how do I test 'em or do I just bin 'em

[dan19evans]

Not really sure there is a way you can test the head or block for leaking into the bores. You won't be able to pressurise the cooling system and check for leaks as the cylinder head will be off...