Nissan Largo Friends

core plug location please . i have water leack at back of engine i feel it is a plug gone. can anyone advice where to get one if it is the core plug

NORMALLY ONE BEHIND FLYWHEEL,GEARBOX NEEDS TO BE REMOVED TO GET TO IT,COULD BE WATER PIPE FROM TURBO TO REAR ENGINE,COULD BE HEAD GASKET ALL SORTS OF POSSIBILITYS,ALSO THINK IS A PLUG ON BACK OF HEAD