I've been able to find coolant leaks by isolating the radiator and heater core to prevent pressure damage, and using a pressure tester to jack up the cooling system pressure way above normal. Connect the top and bottom radiator hoses together, put a loop of heater hose across the heater supply ports, and pump the system up to about 20 PSI or so. If there's a seep leak, it will probably turn into a spray. I've even pressurized a block with a garden hose at times to find pinhole leaks!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!