"O" ring seal on steel heater pipe going into the upper right hand side of the inlet manifold, or pipe going down front right of engine to back of pump?? Water pump gasket?? I find it easier to trace these sort of leaks using a small mirror on a stick and a torch, if that's any help. FWIW, once remedied I add a tub of Barr's leak-seal to every vehicle I've ever owned, it's one of the few sealant types that remains active in suspension in the fluid and won't clog up waterways or radiators. Badger.