Question
Southern California, tree at least 45 years old. It has been healthy for the 37 years we have been enjoying it.
For the first time, beginning a couple of weeks ago, wet spots are developing on the trunk.  Some have grown to two feet in length. There are about a dozen occuring from near ground level to 8 feet up. I detect no odor.  I'd email you a photo if I could.

Answer
Sounds like damage from a flathead borer. These insect bore into the trunk and the tree exudes a sap to try to drown the insect larvae. The best thing to do is spray the damage trunk with an insecticide called Onyx or Merit. Wet the trunk until the solution runs down the trunk. Both will be absorbed into the bark of the trunk killing the insect. You should be able to find these at your local nursery.
Borers usually attack when a tree is under stress. I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Do this now and again in the Fall.