2000 Ford Fiesta repair

Be sure to double check for the leak at all of the hoses, pipes etc. Above the area where the engine and gearbox bolt together. You have to make sure that the leak isn't coming from somewhere else because you'd hate to go through all the work of disconnecting the transmission and then finding out its a hose somewhere and the water is running along the engine and dripping at the rear causing you to think that its the core plug.

If nothing is found, you will have to disconnect the transmission from the engine to find the leak (and in that case it will most likely be a freeze plug [core plug])