Stop Leak stopped the leak. Water levels seem to be holding after several hours of running the engine. We were going to take SV Grace out for a "sea trial" Friday morning, but we have a new development that needs to be pursued first.
Yesterday morning we were heartened by the apparent success of Stop Leak as we torqued all the head bolts (some were loose) to tighten up the head on the head gasket. This was done while the engine was hot, so we had to let the engine cool down overnight, before we adjusted the valves. We ran it this morning with the newly adjusted valves for a good long time. It sounded great and there was no apparent water loss.
This afternoon I pulled a small amount of oil out of the engine for a detailed oil analysis. The analysis can detect impurities like antifreeze in the oil in very minute quantities on the order of one part per million. This was the final check to confirm the head gasket was ok. When I took a close look at the oil in the sample bottle however, I saw many small silver specks. Since Stop Leak is composed of some kind of finely granulated silver metal all bets are off on the head gasket. This morning's first order of business is to get the oil up to the test facility and see what's going on. Maybe head gasket is bad after all.
This would be good news because it would eliminate the "retired" exhaust manifold as the source of the leak. "Retired" is Volvo speak for "no longer being manufactured".
I am not real happy with them. Parts like the exhaust manifold are not usually replaced early in an engine's life. These parts fail only after many years. So just when you would expect to see a spike in the demand for these castings, Volvo has ceased making them, forcing owners to consider repowering......with a Yanmar.