That’s similar to how my Corolla’s water pump attaches. When I recently replaced it both of the old rubber (probably neoprene) o-rings were noticeably distorted and stiff as a board, very much non-pliable. It appeared one of them had actually been leaking, but the other was still continent. The main leak problem tho was the shaft seal, but I can see how those o-rings could become problematic. My truck’s water pump attaches to the block via a normal gasket interface, and while the water pump shaft seal has leaked, the gasket interface has never leaked.
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