Didn't get into the workshop yesterday as I took SWMBO down to visit here sister near Oldham. Going in this morning a little surprise awaited me. There was a small pool of oil under the tractor. At first I thought the sump gasket was weeping. I'd used the old gasket, with a smear of silicon grease either side, as it was undamaged and looked ok. Something I've done many times before.
So off with the engine and onto the bench. Sump off and a new gasket, with a smear of Hylomar jointing compound either side and sump back on. Engine was then left standing on the bench with a refill of oil in. After a while a trace of oil appeared again. That when I noticed it was coming from the sump it's self by bolt hole.
Off with sump again and after a thorough degreasing, no crack was visible. So taking the sump up to the farm I turned the acyt' torch on that corner. Sure enough, as the heat built up a hairline crack became visible, as oil began to appear. I didn't get the area red hot, just enough so all oil contamination was gone.
I have some two part epoxy metal replacement stuff, which I have used with success on a petrol tank. I'll give it a try tomorrow. A layer on the inside over the crack. Nothing to lose and it's got two choices. It'll work or not. We'll see.