Has anyone had a problem with the oil getting into the cooling system

What is your question?

i was driveing and my gage spiked hot so i pulled over right away changed the thermostat ran for two days the ran hot agin at that point i had oil in the radeator so i changed the headgaskets on both sides drove for a week and it overheated agin and there was oil in the cooling system agin pulled the oilcooler off its a one pice cooler thats about 300dollars at ford so i hooked hoses to it and and the water hose to test it and had no leakes so iam thinking a crack in the head inless someone else knows something i dont iam just at a loss cause if it was a crack in the head why did it go a hole week before it did it agin.