After a hot run on Sunday, I noticed an obvious hissing water leak where the water pump housing meets the engine block. This seal had held for three years since I built the engine, but for some reason is seeping now. Before I pop off the assembly and replace the gasket, any new advice of gasket-seal procedures, best sealant, etc?

Form-a-gasket works great. Put it on both sides of the gaskets. I used it for most of my engine gaskets when I rebuilt my engine 30 yrs ago. I dissembled the engine this year with no leaks and the gasket just peels off! No old gasket to scrap off!

When you pull the Timing Cover check it for pitting and flatness.
They can get pretty bad over time around the water ports.

I use the biggest fine tooth flat file I have to work them back smooth. Check with a straight edge.

<for pitting and flatness.
They can get pretty bad over time around the water ports>

Ditto

Mine didn't leak, and I did it as a pm measure.

Mine was deep enough that it would have distorted the mating surface that covers the crankcase area. So I leveled the whole the mating surface, starting with #36 paper on a longboard, and finishing in, I cannot remeber if it were, #320 or #500, followed by a hand-burnish to acheive an origional texture surface.

I don't know if you can still get it, but the only thing I use is Permatex #2 non hardening sealer. I have a large, 32 oz tube, and a 32 oz bottle of brush/ball-in-cap. Both are militar-issue and have a man-date of 1974, and I have had the stuff since I was a kid. (It was at my parents house when I moved to TX and rediscovered when I came back.) I still use it and used it when I 'painted' my engine. I have had 100% sucess rate with #2, and there have been a few 'shady' installs where the surfaces could have been cleaner.

Surgically clean union areas, not so much sealers, is the key to leak-free bonds. Silicone is an excellent invention and cannot be surpassed in some applications. For instance, it's the only way to install headers, either silicone only or as a gasket sealer. But I don't like silicone as a gasket sealer in engine acessory assemblies.

Good info all, appreciate it. Amervo, I'll be up to Maryland to visit family in October and to go to the Redskins-Colts game!

I use the same stuff. They have all sorts of silicone products now. I used it instead of or enhanced gaskets in my engine back in the 80's with Permatex. I torn down the engine this year and it was still working and I peeled it off with my fingers. The only leaks I had were the front and rear seals!