Coolant visible on top of engine
 

1994 88 Royale with 84K miles. I'm not a mechanic so I hope I get description right.

After engine runs for 10 minutes or so and then shut down, there is a visible pooling of liquid which I would think is coolant on the top right front of the engine. The pooling takes some time to be evident. The pooling is just left of the thermostat inside of an indention in what I think is the lower intake manifold and the depth of the liquid is about 1/4". There is also either a bolt or nut inside of this indention. If the liquid is dried-up, with a paper towel for example, it will eventually reappear. This source of the liquid is not apparent while the engine is running.

The oil is not milky and does not appear to have any water in it. Coolant loss does not appear to be a problem. There is some dark gook evident in the coolant when the radiator cap is removed.

Any suggestions on where to start with this situation would be appreciated.