Upon reflection, Check out my problem and it *could* be yours.
I bought the 580D with a "fresh" engine overhaul and somewhat unknown operational history. One day while messing about in the yard, I got steam out of the blowby tube, basicly about as much exhaust as from the stack. I shut her down and pulled the dipstick. Chocolate Milk! :cussing
So, I ordered a head gasket from work and set about tearing down things to
work while having the worst buyer's remorse in recent memory. I almost
had the rocker assembly off when I found a freeze plug loose behind the
rocker stand. I found the hole it goes in. There are three freeze/cup/core
plugs in the top of the head. One on each end and one more or less in the
center. Coolant is in the head and oil is flowing around in the rocker area.
I changed the head gasket for double sure and replaced the offending plug
and it's brothers with extra deep versions with lion's head gasket sealer on them as per ex Case mechanic instructions. Changed oil and coolant and have had no further troubles from it. Turns out my "bad" machine has been
better than I thought after all. Everything in the engine actually was fresh
and nice looking inside.
I suspect yours might be leaking or have a small pinhole in one or more of the
plug. Pull the hood so you can see and pull the valve cover should be all the tearing down needed to inspect. HTH
Dang, I got on a tear I guess.