I have a10k series machine was running it had had no trouble out of it at all shut it down for the night had good oil pressure no heating issues and the next morning it was locked up removed hydralic pump not locked there torque converter spins freely hard to belive it just locked up but I'm fixing to drop the belly pan and oil pan and see what I find
What is the coolant level , has it dropped . Maybe a leaky head has filled a cylinder over night
As epirbalex says, coolant or I would say possibly fuel on a piston. Think coolant most likely, check radiator level. Does starter engage, just wondering. Simon C
Pull the starter and try and bar the engine over at the flywheel.
sugar in the engine oil??
I once had a tractor do that, ran perfect, shut it off and it wouldn’t restart, locked up. Turns out it was just the starter was shot and had jumped a tooth jamming everything up. Removed the starter and it turned over just fine with a bar.
Friend of mine scored Massey 1150 tractor from local boneyard for scrap price, supposedly had locked up engine. When he got it home tried pulling starter and found same thing, starter and bendix locked in fully actuated position into flywheel. After pulling starter engine turned freely. 10 years later still his favorite haymaker.