Internal water leak

[davem201m38]

Hi all,
OK, this winter I'm rebuilding my MC L134 engine. This engine did run fine until I parked it up last winter with plenty of new expensive antifreeze in it. So I was a bit surprised this spring to find the engine locked solid. Dropping the oil I found water in the oil in the sump.
So somehow water had got from the cooling system into the sump. When I get the sump off and strip the block I suspect I'll be looking for a tiny crack or other route for that water.
The last 'rebuild' was by Japan Ord Command, over 60 years ago. It has evidence of a crack on the outer block behind the distributor but this has self sealed long ago. The block will be going to the machine shop and magnafluxing may be an option if the shop does it.
So my question is;
1. What are the typical routes or known points where the engine fails?
2. Anywhere special I should check for a hairline crack?
3. Does magnafluxing work for visible surfaces inside the block?

Ta, Dave.

[oilleaker1]

They like to crack from a head stud into the valve pockets, and possibly the channel or hole the distributor shaft slides down into. Heads can also crack. Machine shops can magnaflux and pressure test blocks. I was told not to clean it or blast it. Magnaflux is easier to see cracks on a rusty dirty block. Check the head gasket for signs of leakage. Obviously the cylinder that has antifreeze in it when you pull the head is the area to study closely. I had a WW2 engine that had a pinhole leaking internally due to a thin casting at the base of the water jacket. I also had a soft plug that leaked down behind the dipstick , oil fill tube and seeped into the engine around the tube. Always something to challenge you. John

[davem201m38]

Ah! Good advice, thank you. The crack behind the distributor could be a suspect.
I'll ask at the shop how they want the block delivering and in what state.
This is a genuine MC engine so I'm pretty keen to preserve it.
As an aside, this jeep stood 30 years in a Greek military scrap yard and the engine started after a light service, but 1 year in an English garage and it's goosed.
Cheers, Dave.

[oilleaker1]

Since the engine was locked, which usually means piston rings rusted, head gasket first. Then cracks. A engine that has run with a leak will burn off the carbon in that leaking cylinder, and with history of the leak will tend to rust and pit the surfaces in the combustion chamber more than other chambers. Unfortunately, I've scrapped three blocks from cracks not fixable. A external crack around the distributor, is quite fixable. I've cleaned and V'd out those and then mig welded them. You weld about a 1/4 inch at a time. Always keeping it cool. Then grind it flat and look. It will re-crack if you got it too hot. Then a covering of JB Weld will seal it for good. The drill, thread, and pin method of internal crack repair is the best way to fix internal cracks. My GPW 1943 block was saved this way and runs excellent. Also: the distributor bore can be salvaged with a length of rigid copper tubing and permatex sealant. Beware if they plane the block surface you can lose your MC XXXXX number. Let us know what they find. I love a good ending. John