I have a milky residue inside of oil cap but no water mixture in oil itself what

I say no problem! Condensation, warmer in the day colder now at night! Keep a check on the coolant level. Good answer #1. Must have been pecking about the same time!

First try to flush, and clean the system. If you still have a milky substance it could be a lower intake manifold gasket.

I also agree with #1