first, welcome aboard
define milky. a slight bit of condensation foam in the valve covers is normal if you idle a lot
if you are generating a milkshake. you have an issue
most thermal-declination-H2O-phase-change structural breaches are from improper winterization. so how did you winterize?
however you could also be in salt water and your manifolds could have rusted to the point of needing to be replaced.
only way to tell. drain the water from the cooling passage and pressure test the block and heads.