I'm sorry. Today I'm being stupid. I should have provided more information. The truck is a 1990 Ram 50 with the 2.4 L engine, "base" model (I can't recall off the top of my head what the engine designation is). The tube that is leaking is on the passenger side of the engine and seems to come out of the water pump, runs to the rear of the engine passing under the exhaust manifold, and then disappears behind the rear of the engine. The leak is just under the rearmost part of the exhaust manifold.

And thank you for taking the time to reply, LSR Mike!