Here is more info in a hurry before.
I had nearly 4-5 gal of coolant get into the oil in about 5 min. I know this from checking the oil first before firing it up to plan on moving the combine. I didnt move it so I shut it off after about 5 min. A pool of oil and coolant was on the floor after it ran.
Right now oil cooler is off. I am going to check it out more in the morning.
If you have a bad oil cooler, you'll have a milkshake both ways as the cooling system holds pressure after the engine is shut down, as oil pressure goes away immediately. This is of course assuming that you get the system to operating temp.
If you take the head off make sure you get it magnafluxed for cracks at a machine shop, especially if no other obvious problem is found. Check the liners closely for cracks too. This past harvest I had a 9600 with the same symptoms as yours and it was a fine crack running vertically on #3 liner. Only 4000 hrs on the engine, far from worn out.
That depends on what you find, how many hours you have on it, and if you do the work yourself. I would first get the engine to were you can pull the pan and fill it with coolant and see if you can visually see were the coolant is draining from. You may need to put a couple of pounds of pressure to it to get the coolant flowing. Or-rings and cracked liners should be easy to see.
I guess I like to know what I am up against so I know what option works best for me.
A complete overhaul kit is about $2600. Getting the head done at a machine shop will run you roughly $1000. Then there's oil, coolant, injectors, etc. You could be up and running with a fresh rebuild for around 4 grand if the major components are ok.