During my manifold replacement I guess I didn't drain quite enough coolant before I removed it because the coolant passages dumped some antifreeze in the lifter galley and then into the oil. I drained the oil the next day and the engine didn't run in the meantime...I didn't bother to change the filter because I didn't see how water could get in there without the pump being active. The car is running again but when I checked the dipstick there were signs of moisture and even a little white . Granted I'm an idiot for letting this happen in the first place but if I drain the oil will it be okay?
If you change the oil & filter again and it still does it, you might need to re-check your gasket. I had to re-do the intake gasket on my Grand Marquis because of the oil & coolant mixing.
I jusat swapped on my ported heads.It's almost a done deal that water is going to get in there.I ran a quart of engine flush (with the old oil and filter),drained the pan,letting everything drip out thoroughly,then added the Syntec and new filter.All good to go.Plus,the engine flush will help get rid of any built up that may be in the engine that you don't know about.Good luck.
Check the gasket for leaks. If you drained the oil the coolant should have come out too so I'm guessing you have a leaky gasket.