Replacing Freeze Plugs
When coolant goes bad you may find a freeze plug leaking. They usually rot from the inside out. So, when you see one leaking, and you replace it, check the backside of it. If it's rusted out from the inside out you'll most likely have a another coolant leak real soon. When I see this condition I find it easier to simply pull the engine so we can get to them all and drive the new ones in straight. Here's one way to do it.