Sheared bolt.

While underneath the engine, cleaning the lower balance shaft housing, before resealing it, I noticed that a bolt was missing from the oil pan. Unfortunately the shank was still inside the block. It broke pretty deep, about 1cm inside the hole. drilling it out was also a problem, since in order to get on it, I had to drill between the oil pan sump, and crossmember. 

After drilling the bolt as far as i could get with a 6 inch drill bit, I tried removing it with a screw extractor. The was no way of turning the extractor, that has a 1/4 inch hex end, since the bolt is buried so deep between other components.

Some modification was required. I pounded a 1/4 inch hex nut on the end of the extractor, so I could turn it with a socket on a long extension. This worked, but instead of removing the bolt, it was chewing it up. I needed the extractor to bite. Trimming the tip, made it less likely to bottom out, but it still was not enough.
I finally found a bit long enough in a co-worker's tool box. It was thinner than I needed it to be, but that ended up being fine.

I finally removed the broken bolt by drilling it very deep. It only had 1.5mm till I came out the other side. I was a bit paranoid about drilling through the aluminum block, so I periodically checked the swarf with a magnet. Of course this would have been much easier to do with the oil pan off, but that is a pretty involved job. Engine should be supported from above, steering rack removed, crossmemeber removed..etc... It would benefit from a new gasket, but if I do pull it out, the rod bearings should be changed. Too many things are in pieces right now for me to start something else.