Phil, many years ago my Dad had the fan belt break on his 454 with D-179 Diesel while plowing. Before he noticed the temp gauge was well in the red and the rad boiling over. After the boil over it would leak coolant into the crankcase over night when it was cool. He had to finish plowing and other fall work before he could have O-rings replaced. So he only put rad cap on just enough to hold it and every morning he would open crankcase drain plug enough to let coolant drain. But as weather got colder it would leak more and if he was not using for a few days he would drain the coolant out of the block. After he was finished with the tractor, he had the local IH dealer replace the cylinder O-rings. My brother has the tractor today and it has well over 15,000 hours on it and engine is still running strong.
I am not recommending the above as it is your tractor. I am just stating my Dad's experience, be it good or bad.