You can check whether a nearby heater hose/pipe junction is not the cause of the leak, or if it is coming out of the bell housing. However, at your mileage and time of ownership, you should see your dealer for warranty service. There is no soft plug at the back of the camshaft hole, just an o-ring seal to the aluminum block plate from 2003-up. Up to about 1996, there was a flat type soft plug, and after that it was backed up with an o-ring between the plug and the camshaft. This plug or o-ring would leak oil, not coolant. There are no coolant soft plugs inside the block plate/bell housing area. There is one on the rear of the block above the block plate and under the cylinder head.