Hello, i recently purchased a MQ with the SD33T engine wich havent been started for 7-8 years,

Last night i was getting ready to start the engine and 1st thing i did was check oil and coolant, and i suspected thelre was no coolat at all.
So there i am putting the coolant in the radiator and at some point i hear the coolant droping in the oil pan and immediately stoped adding more.Checked the oil via the dipstick and it was just like i suspected...coolat in oil pan.

Today i removed the oil cooler because someone told me that it could be cracked and coolant could be leaking from there but i didnt noticed any damage and there was no sludge build up.

Anyone with an idea where to look next? Could it be a head gasket or blown head?