After I graduated from law school I was not working while I was studying for the bar. When I left the grocery store one afternoon the car (1976 Datsun F-10 hatchback, one of the ugliest things ever to grace a showroom) barely started to crank and that was it. I knew by the sound it wasn't the starter or battery and just to confirm I tried to push start it, and it locked the rear tire when I let out the clutch.

I pulled the spark plugs and cranked it over, and got a gush of coolant from one of the cylinders, so I figured it blew a head gasket. I pulled the dipstick and was happy to see no evidence of coolant in the oil, so I knew it had just happened and wasn't something that had been building up over time.

However, on pulling the head I found that the aluminum had corroded, pitted and ultimately failed between the edge of the combustion chamber and the water jacket, so that coolant had just poured into the cylinder. Since I was broke and there weren't any serviceable heads in wrecking yards, I took a Dremel tool and some small bits and cleaned up the corroded area until it was all bare metal; I didn't make it smooth but left lots of valleys. Then I mixed up some JB Weld and really forced it into all the little gaps, building it up until it was a little higher than the mating surface. I let it cure for 24 hours, then filed and sanded it back down to flush. I sprayed a new head gasket with copper coat, and then reassembled. I also changed the oil.

I owned the car for a couple more years after that and then engine was still fine when I sold it. That really surprised me, and it sure made me a believer in the folks behind JB Weld products.