Claude,
Welcome to the TBN forums. Hope we can help you.
Condensation could be the cause if there was only a little water in the engine oil. But I think that would be more likely if you frequently started the motor for only a short time and didn't let it get hot, or if the tractor sat through a lot of warm/cold cycles. Did you find the water when changing the oil? If so, and you find the new oil also gets water in it, there are other possible causes:
If you have a gear-driven water pump, you could have a problem if the water pump is going bad. If the water pump bearings are worn the impeller shaft wobbles, and then the seal on the impeller shaft will fail, and water will leak into the chamber housing the drive gear. This chamber normally has a weep hole to let that leaking water out, but if the weep hole is plugged up, the water could be forced past the seal on the shaft that holds the gear and into your crankcase. You can check this pretty easily by cleaning the weep hole and checking for water the next time you run the engine at normal operating temperature for a while. If water shows up, then you need to replace the pump.
You could also have a head gasket problem, which would be more likely if the engine has become severely overheated at some time.
Or, as you suggested, you could have a cracked cylinder wall.
Is your tractor under roof? If not, and if it has a vertical exhaust pipe, over a long period of just sitting, I suppose rain could enter there and eventually reach your oil pan, but I think that's very unlikely.
If these suggestions don't help or you have more questions, post again. And please make a final post explaining what the problem was so future readers can benefit from your experience.
