The front freeze plug on the passenger side of the engine on my 240z has been leaking and we can't figure out why. 2 days ago we replaced it with a new brass one and used gasket sealer all around it. Today there is another drip of coolant that came out of it. Anyone know why the freeze plug would develop a drip leak? It doesn't seem possible that the plug could be leaking again considering that we put a good amount of gasket sealer around the edges of the new plug when we installed it.

Have you examined closely, with a magnifying glass, the condition of the block?

I'll have to do that tomorrow. What exactly should i be looking for? The coolant leaks out of the bottom edge of the freeze plug, so i suppose their could be an imperfection in the block, but before the engine was rebuilt none of the freeze plugs ever leaked. If there is an imperfection in the freeze plug hole, then I would just have to use better sealant when installing another freeze plug, correct?