Reply to Jdz:
Mine went when I left it idling and walked away from the machine to help someone out with something else. It sprung a leak at the oil filter canister. By the time I ran back to the machine, it was too late.
Things have a way of sneaking up you,and many of the old machines don't have a lot of history to help the current owner.
A 9u D6 I bought at scrap iron price because steer clutches were rusted. Runs very well,track doesn't want climb the rollers.Quickly became my favorite. But does use a bit of oil. Was planting a 120 acres of safflower,without irrigation. So when the soil needs worked you have to go.
My practice has been fuel at the end of the day,and check oil. Rather than need oil it was full,and maybe thin. A oil change would not hurt,done the next morning. Checked at noon,and is it sitting level or not,that evening it is over full. So the question was run it another 8 or 10 hours or park it. As I had no other tractor fit to run, I called and found a tractor.
It sat in the yard some weeks before it got worked on. In that time fuel kept dripping through pump and crankcase was at the point of having fuel ready to overflow out the dipstick.
From keeping my ears open to others tails of woo,I think this was a bigger failure than many. But my advice would be you never know how fast it will start leaking,or when it will get worse fast. It is less than a $100 for all new seals and gaskets to fix the problem. Depending how handy you are it is a half a day project to fix, give or take. If you have real handy lifting devices it could be a one man project. I had 2 young backs on hand as well as myself and the neighborhood want to be know it all. Very easy with the help of the people here that had me well prepared for what we would find.
Mister know it all didn't want to believe the advice from here that the old seal would look square. But it is truly just a big fat o-ring that becomes square from the space it fits in. Sadly mister know it all has passed and is not around it impart what he learned that day.
I don't think I will change the o-ring seals in all my tractors just because. But will not run one once I see the oil level coming up on the dipstick.