possible that someone had the tractor apart at some point, then upon reassembly of the front frame they used the incorrect bolt(s). With them being too long and installed by a gorilla it will punch right through the back side of the block, obviously causing leak. Or another scenario which I am guilty of. There is possibility that when a bolt was installed there was some silicone, grease, water, anything noncompressable in the back of the hole. When you tighten the bolt against the noncompressable, it becomes a really really powerful hydraulic "cylinder" except the back side usually blows out and the result is the same as using a bolt that is too long or not "washered" properly. I did it on a transmission housing and it cost me about $3700 (it cost ME that much, a tech) to fix it. Had to replace the housing, it was the only way to properly do it. If it were mine (and it wasn't) I'd have patched it but when you deal with other peoples' stuff you fix it right or don't bother touching it. In my case it was SILICONE (sealant, liquid gasket) that wasn't cleaned out of the hole.
look at your parts breakdowns and see if it shows a bolt in that hole. If it does, someone likely put the wrong one in at some point and broke the block. If it doesn't there's still a possibility. You should be able to clean it up and have a look-see into the bolt hole, may have to use a mirror or something to see it but it will usually be obvious once you get the junk outta the hole. Or see if you can stuff a coat hanger or something in it (engine off of course) it shouldn't go in very far.
