Today I couldn't get the car to start (unrelated problem?), so when I came home, I inspected the engine area with the engine running.

I could not smell/see any exhaust anywhere around the block (so no crack in the block then...) and in doing so I saw this drain plug. Plug is intact and there is nothing leaking/no wetness anywhere around it. In fact, the only wetness anywhere around the block at all is on the middle of the head from the slightly leaking valve cover gasket.

Apart from the pressure test/repeated visual inspections, I would only guess that my head gasket is the vanishing coolant culprit.

Out of curiosity, with a small leak like this one, is it acceptable to drive the car around without risking catastrophic engine damage?

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87 300E
202k on the clock