We have a skidder with a detroit diesel in it we are having oil cooler problems, how do we fix it?

What do you mean ? A logging skidder ? Sorry, I was a faller . I imagine that you can fix it the same way you fix a car's oil cooler. By making sure there is no coolant leaking into the oil. If it does you have a leak. Replace the whole system. I know you are losing money everyday the skidder stays parked.