I delveloped a major coolant leak as I was about 30 yards away from pulling into my garage. I did not know of the leak until I saw the trail of coolant in the street after getting out of my car. The engine was running fine and I did not have any signs of an engine problem. The coolant is leaking from an opening at the bottom rear of the bell housing. The radiator drained empty. When I poured more water into the overflow tank. it immediately flowed very fast out of the opening. See the opening in the picture. What is this opening for? Could a frost plug failed? Any other ideas? Help

 

There are frost plugs in the rear iron...so likely that's whats up

 

OP, just came to your thread after PM, and yes what I said we call welsh plugs in Australia (frost plug) MMC Japan calls them Plug/Blind.
These are not a 'common' problem , but as I said it is usually engine out to either renew the plug , about 5 of them are in rear housing iron depends on which any one is possibly leaking, one might get to it from removing Transmission on a hoist and flywheel (manual), but it is not a quick and easy fix as again much depends on which Plug is leaking, or find out why it is leaking (usually corrosion from old coolant, using tap water, etc).

Having said that you have a lot of coolant coming out, usually but not always leaks from welsh plugs are a slow one, a welsh plug is made of soft metal (used to be brass in banger engines) and is then pressed into the much harder Iron Rotor Housing ( the end black one).

Even though you joined in 2012 you don't have enough posts counts.